Facultative bacterial endosymbionts in insects have been under intense study during the last years. Endosymbionts can modify the insect＇s phenotype, conferring adap- tive advantages under environmental stress. This s...Facultative bacterial endosymbionts in insects have been under intense study during the last years. Endosymbionts can modify the insect＇s phenotype, conferring adap- tive advantages under environmental stress. This seems particularly relevant for a group of worldwide agricultural aphid pests, because endosymbionts modify key fitness-related traits, including host plant use, protection against natural enemies and heat tolerance. Aimed to understand the role of facultative endosymbionts on the success of introduced aphid pests, the distribution and abundance of 5 facultative endosymbionts （Hamiltonella defensa, Regiella insecticola, Serratia symbiotica, Rickettsia and Spiroplasma） were stud- ied and compared in 4 cereal aphids （Sitobion avenae, Diuraphis noxia, Metopolophium dirhodum and Schizaphis graminium） and in the pea aphid Acyrthosiphon pisum complex from 2 agroclimatic zones in Chile. Overall, infections with faeultative endosymbionts exhibited a highly variable and characteristic pattern depending on the aphid species/host race and geographic zone, which could explain the success of aphid pest populations after their introduction. While S. symbiotica and H. defensa were the most frequent endosym- bionts carried by the A. pisum pea-race and A. pisum alfalfa-race aphids, respectively, the most frequent facultative endosymbiont carried by all cereal aphids was R. insecticola. Interestingly, a highly variable composition of endosymbionts carried by S. avenae was also observed between agroclimatic zones, suggesting that endosymbionts are responding differentially to abiotic variables （temperature and precipitations）. In addition, our findings constitute the first report of bacterial endosymbionts in cereal aphid species not screened before, and also the first report of aphid endosymbionts in Chile.展开更多
The maternally heritable endosymbiont provides many ecosystem functions.Antibiotic elimination of a specific symbiont and establishment of experimental host lines lacking certain symbionts enable the roles of a given ...The maternally heritable endosymbiont provides many ecosystem functions.Antibiotic elimination of a specific symbiont and establishment of experimental host lines lacking certain symbionts enable the roles of a given symbiont to be explored.The whitefly Bemisia tabaci(Gennadius)in China harbors obligate symbiont Portiera infecting each in-dividual,as well as facultative symbionts,such as Hamiltonella,Rickettsia and Cardinium,with co-infections occurring relatively frequently.So far no studies have evaluated the selectivity and efficacy of a specific symbiont elimination using antibiotics in whiteflies co-infected with different symbionts.Furthermore,no success has been achieved in estab-lishing certain symbiont-free B.tabaci lines.In this study,we treated Hamiltonella infected B.tabaci line,Hamiltonella-Rickettsia-co infected line and Hamiltonella-Cardinium co-infected line by feeding B.tabaci adults with cotton plants cultured in water containing ri-fampicin,ampicillin or a mixture of them,aiming to selectively curing symbiont infections and establishing stable symbiont-free lines.We found ampicillin selectively eliminated Cardinium without afecting Portiera,Hamiltonella and Rickettsia,although they coex-isted in the same host body.Meanwhile,all of the symbionts considered in our study can be removed by rifampicin.The reduction of facultative symbionts occurred at a much quicker pace than obligate symbiont Portiera during rifampicin treatment.Also,we measured the stability of symbiont elimination in whitefly successive generations and established Rickettsia-infected and Cardinium-infected lines which are absent in natural populations.Our results provide new protocols for selective elimination of symbionts co-existing in a host and establishment of different symbiont-infected host lines.展开更多
Bacterial endosymbionts of sap-sucking insects provide their host with a num- ber of beneficial qualities,including the supply of nutrition,defense against parasitoids, and protection from heat stress.Damage to these ...Bacterial endosymbionts of sap-sucking insects provide their host with a num- ber of beneficial qualities,including the supply of nutrition,defense against parasitoids, and protection from heat stress.Damage to these bacterial associates can therefore have a negative impact on the fitness of their insect host.We evaluated observational and experi- mental factors regarding the normative hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera:Adelgidae)to help understand the roles of its three recently identified symbionts,including under heat stress conditions.The prevalence of A.tsugae's facultafive symbiont (Serratia symbiotica)was examined at different spatial scales to determine how variable infection rates are for this symbiont.There was no significant difference found in infection rates between adelgids on a tree,within a plot,or within a state.However, significantly more adelgids in Georgia (95%)had S.symbiotica compared to those in New York (68%).Microsatellite genotyping of the adelgids found that this difference was most likely not the result of a second introduction ofA.tsugae into eastern North America.Comparison orS.symbiotica proportions between first and fourth instars showed that symbiont absence did not affect the ability ofA.tsugae to survive aestivation.Evaluations of sym- biont densities within each adelgid found that when S.symbiotica was absent,the density of obligate symbionts was significantly higher.Exposure to heat stress (32.5℃)was not consistently correlated with changes in symbiont densities over a 4-d period.Overall,we have shown that symbiont prevalence and densities vary within the broad population of A.tsugae in eastern North America,with potentially significant effects upon the ecology of this important pest.展开更多
Methanogenic endosymbionts are the only known intracellular archaeans and are especially common in anaerobic ciliated protists.Studies on the evolution of associations between anaerobic ciliates and their methanogenic...Methanogenic endosymbionts are the only known intracellular archaeans and are especially common in anaerobic ciliated protists.Studies on the evolution of associations between anaerobic ciliates and their methanogenic endosymbionts offer an excellent opportunity to broaden our knowledge about symbiosis theory and adaptation of eukaryotes to anoxic environments.Here,the diversity of methanogenic endosymbionts was analyzed with the addition of nine anaerobic ciliate populations that were newly studied by various methods.Results showed that diverse anaerobic ciliates host methanogenic endosymbionts that are limited to a few genera in orders Methanomicrobiales,Methanobacteriales,and Methanosarcinales.For the first time,anaerobic ciliates of the classes Muranotrichea and Prostomatea were found to host methanogenic endosymbionts.Distinct origins of endosymbiosis were revealed for classes Armophorea and Plagiopylea.We posit that armophoreans and plagiopyleans might have harbored Methanoregula(order Methanomicrobiales)and Methanocorpusculum(order Metha-nomicrobiales),respectively,as methanogenic endosymbionts at the beginning of their evolution.Subsequently,independent endosymbiont replacement events occurred in methanogen-ciliate associations,probably due to ecological transitions,species radiation of ciliate hosts,and vertical transmission bottlenecks of endosymbionts.Our results shed light on the evolution of associations between anaerobic ciliates and methanogens,and identifies the necessary preconditions for illustrating mecha-nisms by which endosymbioses between these partners were established.展开更多
The brown planthopper, Nilaparvata lugens St?l, has become a major threat in tropical Asian and China since the rice green revolution of the 1960 s. Currently, insecticide application remains the primary choice for co...The brown planthopper, Nilaparvata lugens St?l, has become a major threat in tropical Asian and China since the rice green revolution of the 1960 s. Currently, insecticide application remains the primary choice for controlling this rice insect pest, but heavy use of insecticides poses dangerous risks to beneficial natural enemies and pollinators, and stimulates N. lugens reproductivity, and has caused a resurgence of the pest in the major rice-planting regions throughout Asia. Achieving the long-lasting goal of sustainable management of N. lugens requires understanding of the molecular basis of outbreaks of the pest and the development of environment-friendly pest-control strategies. Here, we review the recent molecular advances in N. lugens research on the aspects of its endosymbionts, virus transmission, insecticide resistance, and interaction between N. lugens and rice plants. We also put forward further research directions that may shed some lights on management of the rice pest.展开更多
The invasive insect pest, red palm weevil (RPW), Rhynchophorus ferrugineus, poses a significant threat to date production, causing substantial economic damage. If uncontrolled, RPW leads the severely infested host tre...The invasive insect pest, red palm weevil (RPW), Rhynchophorus ferrugineus, poses a significant threat to date production, causing substantial economic damage. If uncontrolled, RPW leads the severely infested host tree to collapse and eventually die. The symbiotic associations with microorganisms and RPW in their gut may help their host insects’ establishment, development, nutrition assimilation, and survival. The objective of this research was the molecular characterization of the microbiome of RPW. In this study, the microbiome was compared among different tissues in females and males of RPW of three different morphs and larvae collected from date palm plantations in the Kingdom of Bahrain. A 251-bp segment of bacterial 16S rRNA was amplified by PCR, sequenced, and processed using the bioinformatics platform QIIME2. One ASV, corresponding to the obligate weevil symbiont Nardonella, predominated in adult female samples, constituting 56 ± 7% of total reads, but was less dominant in male samples (12 ± 3%) and larval samples (2.6 ± 1.9%). For females, samples that included reproductive tissues were almost entirely composed of Nardonella (88% - 99%). When Nardonella was excluded from analyses, there were no differences between adult females and adult males, but larval samples were more species-rich and differed in microbial composition from adults. There were no consistent differences in the microbiomes among morphs. Several specimens showed evidence of infection with host-specific strains of Spiroplasma-like members of the Entomoplasmatales, which are often pathogens or vertically transmitted symbionts. Such close microbial associates deserve additional attention as potential routes to control this destructive date palm pest.展开更多
Pederin belongs to a group of antitumor compounds found in terrestrial beetles and marine sponges. It is apparently used by some members of the rove beetle Paederus as a chemical defense against predators. A recent cl...Pederin belongs to a group of antitumor compounds found in terrestrial beetles and marine sponges. It is apparently used by some members of the rove beetle Paederus as a chemical defense against predators. A recent cluster analysis of the putative pederin biosynthesis gene （ped） strongly suggests that pederin is produced by bacterial symbionts. This paper reviewed the criteria for proving symbiontic origin of bioactive metabolite, indirect and molecular evidences for pederin bacterial origin, as well as three sets ofped clusters and putative biosynthesis process of pederin.展开更多
Brasenia schreberi (water shield), a perennial freshwater aquatic plant of the family Nymphaeaceae, is rich in polysaccharides with positive biological activity and potential application value. As an indicator plant o...Brasenia schreberi (water shield), a perennial freshwater aquatic plant of the family Nymphaeaceae, is rich in polysaccharides with positive biological activity and potential application value. As an indicator plant of the environment in wetlands, B. schreberi original and wild water environment faced increasing deterioration and has been listed as a critically endangered species in several countries of East Asia. Seeking an alternative method to produce B. schreberi mucilage polysaccharide is of top priority. The morphological structure of the stem and leaf of B. schreberi was studied. Well-developed glandular cells and aerenchyma tissue were observed in the stem and leaves of water shield, which were related to its aquatic habitat and polysaccharide secretion and then three endophytic bacteria were successfully isolated and purified from its stem and leaf and identified as Micromonospora sp. YG-1, Xylariaceae sp. strain UT-X and Psychrobacter pulmonis strain T-15. Symbiotic bacteria from B. schreberi produced polysaccharides with similar spectral peaks and chemical functional groups to those of B. chinensis. Further, analysis of hydroxyl free radicals showed that symbiotic bacteria in water shield had significant antioxidant activity against hydroxyl free radicals. This study provides a theoretical and practical basis for further study using symbiotic bacteria to produce polysaccharides to overcome the environmental limitations of the growth and development of B. schreberi.展开更多
Insect symbionts Wolbachia used for pest population control has focused on vector pest species and agricultural insects while rare reports in Chinese stored-product insect samples.In this paper,we surveyed the prevale...Insect symbionts Wolbachia used for pest population control has focused on vector pest species and agricultural insects while rare reports in Chinese stored-product insect samples.In this paper,we surveyed the prevalence of Wolbachia using a PCR detection method in ten Tenebrionidae stored-product insects.Subsequently,the spatiotemporal Wolbachia infection dynamics in Tribolium confusum and Wolbachia elimination patterns using tetracycline treatment were investigated in detail by TaqMan®probe real-time quantitative PCR,and host reproductive fitness parameters were compared.T.confusum was the only Wolbachia infected species in all the surveyed species.Wolbachia infection density consistently increased with the development of T.confusumand plateaued at 3.7×107 wsp copies per individual insect at the young adult stage.Wolbachia densities in females were higher than that in males with a significant difference at the pupae stage and varied among different tissues and organs.Uninfected female beetles were completely incapable of producing mature progenies when crossed with Wolbachia infected males.Embryogenesis and egg hatch rate were specifically inhibited after Wolbachia elimination,while other traits,including the number of eggs,pupation rate and sex ratio,remained unaffected by tetracycline treatment.Our results showthat the TaqMan®probe qPCR is a reliable detection method for quantifying the density of Wolbachia as compared to qualitative detection of wsp gene by PCR and relatively quantified by real-time qPCR.The fitness results indicated that Wolbachia infection was not an obligate symbiont and benefited the host confused flour beetle.展开更多
The structures of bacterial communities in the brown planthopper （BPH） Nilaparvata lugens （St^l） from different geographic and resistant virulent populations were analyzed by using denatured gradient gel electroph...The structures of bacterial communities in the brown planthopper （BPH） Nilaparvata lugens （St^l） from different geographic and resistant virulent populations were analyzed by using denatured gradient gel electrophoresis （DGGE）. Results showed that the bacterial communities in BPH nymph from the first to the fifth instars varied with nymphal growth and development. The bacterial communities in the first-instar BPH nymph were similar to those in adults. Nine geographic BPH populations were divided into three groups based on the cluster analysis of DGGE fingerprint. The first group was from the Philippines; the second group was from Thailand and Hainan, Yunnan and Zhejiang provinces of China; and the third group was from Vietnam and Guangxi, Hunan and Jiangxi provinces of China. BPH populations adapted to different resistant rice varieties. The BPH populations from Mudgo （with resistant gene Bphl） and ASD7 （with resistant gene bph2） differed with those of the susceptible rice variety TNI.展开更多
Astome ciliates live in the digestive tract of a broad spectrum of marine, freshwater, and terricolous annelids. In aquatic lumbriculid and criodrilid oligochaetes collected in Central Europe, we rediscovered three in...Astome ciliates live in the digestive tract of a broad spectrum of marine, freshwater, and terricolous annelids. In aquatic lumbriculid and criodrilid oligochaetes collected in Central Europe, we rediscovered three insufficiently known astomes: Hoplitophrya secans, Mesnilella clavata, and Buchneriella criodrili. Their morphology was studied using in vivo observation, protargol, and dry silver nitrate impregnation. Multiple nuclear and mitochondrial molecular markers were used to determine their phylogenetic positions and reconstruct their evolutionary history. According to our phylogenetic analyses: (1) mouthless ciliates isolated from annelids form a robustly supported monophylum within the class Oligohymenophorea, (2) the progenitor of astomes invaded the digestive tract of marine polychaetes during the Paleozoic era, (3) lumbricid earthworms likely served as a source of astomes for criodrilid, almid, and megascolecid earthworms, (4) the ancestral host of the earthworm-dwelling astome clade led an endogeic lifestyle, and (5) there were multiple independent transfers of astomes from endogeic to epigeic and anecic earthworms. These findings support previous views of the annelid phylogeny, suggesting that astomes reside and evolve in tandem with annelids for several hundred million years.展开更多
Aphids are sap-feeding plant pests that depend on their symbiotic relationships with the primary endosymbiont Buchnera aphidicola to adapt to impoverished diets. However, how the host plant affects the aphid primary s...Aphids are sap-feeding plant pests that depend on their symbiotic relationships with the primary endosymbiont Buchnera aphidicola to adapt to impoverished diets. However, how the host plant affects the aphid primary symbiont and aphid adaptation to host plant transfer are poorly known. In this study, aphid symbiont screening and genotype identification were used to establish 2 aphid strains (Rhopalosiphum maidis [Rm] and Rhopalosiphum padi [Rp] strains) containing only Buchnera without any secondary symbionts for both wheat aphid species (R. maidis and R. padi). Aphid fitness and Buchnera titers were unstable on some of these host plants after transferring to novel host plants (G1–G5), which were influenced by host plant species and generations;however, they stabilized after prolonged feeding on the same plants for 10 generations. The electropenetrography (EPG) records showed that the allocation of aphid feeding time was significantly distinct in the 6 host plants;aphids had more intracellular punctures and spent more nonprobing time on green bristlegrass which was not conducive to its growth compared with other plants. The content of soluble sugar, soluble protein, and amino acid in the leaves of the 6 host plants were also clearly separated. The correlation coefficient analysis showed that the nutrient contents of host plants had significant correlations with aphid feeding behaviors, fitness, and Buchnera titers. In the meantime, aphid fitness, and Buchnera titers were also affected by aphid feeding behaviors. Also, Buchnera titers of aphid natural populations on 6 host plants showed a visible difference. Our study deepened our understanding of the interaction among aphids, endosymbionts, and host plants, indicating that the host plant nutrient content is a predominant factor affecting aphid adaptation to their diet, initially affecting aphid feeding behaviors, and further affecting aphid fitness and Buchnera titers, which would further contribute to exploiting new available strategies for aphid control.展开更多
Hemipteran and dipteran insects have behavioral,cellular and chemical strategies for evading or coping with the host plant defenses making these insects particularly destructive pests worldwide. A critical component o...Hemipteran and dipteran insects have behavioral,cellular and chemical strategies for evading or coping with the host plant defenses making these insects particularly destructive pests worldwide. A critical component of a host plant＇s defense to herbivory is innate immunity. Here we review the status of our understanding of the receptors that contribute to perception of hemipteran and dipteran pests and highlight the gaps in our knowledge in these early events in immune signaling. We also highlight recent advances in identification of the effectors that activate pattern-triggered immunity and those involved in effector-triggered immunity.展开更多
Wolbachia can profoundly influence the survival, reproduction, and defenses of insect hosts. These interactions could potentially be harnessed for managing pests or insecttransmitted diseases. Diaphorina citri Kuwayam...Wolbachia can profoundly influence the survival, reproduction, and defenses of insect hosts. These interactions could potentially be harnessed for managing pests or insecttransmitted diseases. Diaphorina citri Kuwayama is a phloem-feeding pest capable of transmitting the putative causal agent of citrus greening, Candidatus Liberibacter asiaticus (CLas). Like many insects, D. citri is also infected with Wolbachia (wDi). Recent studies indicate that the relative abundance of wDi could be associated with the abundance of CLas, and that wDi may contribute to regulating expression of phage lytic cycle genes in CLas, suggesting the need for better understanding of wDi biology in general. This study investigated the genetic diversity of wDi among D. citri in populations spanning eleven countries and two U.S. territories. Six Wolbachia genes, wsp, coxA.fbpA.ftsZ, gatB, and hep A, were sequenced and compared across samples. Two prevalent wDi strains were identified across the samples, and screening of clone libraries revealed possible coinfection of wDi strains in specific populations. D. citri mitochondrial cytochrome oxidase subunit I gene (mtCOI) were more divergent between D. citri populations that were infected with different wDi strains or had different infection statuses (single infection vs. coinfection). While we could not eliminate the possibility that maternal transmission may contribute to such patterns, it is also possible that wDi may induce cytoplasmic incompatibility in their host. These fin dings should contribute to the understanding of wDi population ecology, which may facilitate manipulation of this endosymbiont for management of citrus greening disease worldwide.展开更多
Bemisia tabaci-transmitted geminiviruses are one of the major threats on cassava and vegetable crops in Africa. However, to date, few studies are available on the diversity orB. tabaci and their associated endosymbion...Bemisia tabaci-transmitted geminiviruses are one of the major threats on cassava and vegetable crops in Africa. However, to date, few studies are available on the diversity orB. tabaci and their associated endosymbionts in Africa. More than 28 species have been described in the complex ofB. tabaci cryptic species; among them, 2 are invasive pests worldwide： MED and MEAM1. In order to assess the species diversity orB. tabaci in vegetable crops in Senegal, several samplings in different localities, hosts and seasons were collected and analyzed with nuclear （microsatellite） and mitochondrial （COI） markers. The bacterial endosymbiont community was also studied for each sample. Two species were detected： MED Q1 and MEAM1 B. Patterns of MED Q1 （dominance on most of the samples and sites, highest nuclear and mitochondrial diversity and broader secondary endosymbiont community： Hamiltonella, Cardinium, Wolbachia and Rickettsia）, point toward a predominant resident begomovirus vector group for MED Q 1 on market gardening crops. Furthermore, the lower prevalence of the second species MEAM1 B, its lower nuclear and mitochondrial diversity and a narrower secondary endosymbiont community （Hamiltonella/Rickettsia）, indicate that this genetic group is exotic and results from a recent invasion in this area.展开更多
Immunofluorescence has been widely used to localize microbes or specific molecules in insect tissues or cells.However,significant autofluorescence is frequently observed in tissues which can interfere with the fluores...Immunofluorescence has been widely used to localize microbes or specific molecules in insect tissues or cells.However,significant autofluorescence is frequently observed in tissues which can interfere with the fluorescent identification of target antigens,leading to inaccurate or even false positive fluorescent labeling.The alimentary canal of the potato psyllid,Bactericera cockerelliŠulc,exhibits intense autofluorescence,hindering the application of immunolocalization for the detection and localization of the economically important pathogen transmitted by this insect,“Candidatus Liberibacter solanacearum”(Lso).In the present study,we tested the use of irradiation,hydrogen peroxide(H2O2)and Sudan black B(SBB)treatments to reduce the autofluorescence in the B.cockerelli alimentary canal tissues.Furthermore,we assessed the compatibility of the above‐mentioned treatments with Lso immunolocalization and actin staining using phalloidin.Our results showed that the autofluorescence in the alimentary canal was reduced by irradiation,H2O2,or SBB treatments.The compatibility assays indicated that irradiation and H2O2 treatment both greatly reduced the fluorescent signal associated with Lso and actin.However,the SBB incubation preserved those target signals,while efficiently eliminating autofluorescence in the psyllid alimentary canal.Therefore,herein we propose a robust method for reducing the autofluorescence in the B.cockerelli alimentary canal with SBB treatment,which may improve the use of immunofluorescence labeling in this organism.This method may also have a wide range of uses by reducing the autofluorescence in other arthropod species.展开更多
Male-killing is 1 of 4 known strategies that inherited parasitic endosymbionts have evolved to manipulate their host＇s reproduction. In early male-killing, infected male offspring are killed early in embryogenesis. W...Male-killing is 1 of 4 known strategies that inherited parasitic endosymbionts have evolved to manipulate their host＇s reproduction. In early male-killing, infected male offspring are killed early in embryogenesis. Within the Insecta, male-killing bacteria have been found in a wide range of hosts. The Coccinellidae families of beetles, better known as ladybirds, are particularly prone to male-killer invasion. In samples of the coccinellid, Coc- cinula crotchi, from Japan, a new male-killing bacterium was revealed by phenotypic assay. Molecular genetic analysis revealed the identity to be a tetracycline-sensitive Flavobac- terium that causes female-biased offspring sex ratio. Furthermore, that Flavobacterium strain was found to be closely related to the Flavobacterium causing male-killing in the congeneric Japanese coccinellid, Coccinula sinensis, which was collected from the same region. However, we found slightly different Flavobacterium strains infecting C. sinen- sis from regions with different environmental conditions. This may be an indication of horizontal transmission of male-killing Flavobacterium between these 2 ladybird spices. Finally, environmental conditions may affect the spread of male-killing bacteria among their hosts.展开更多
Larvae of the diamondback moth, Plutella xylostella L. （Lepidoptera： Plutelli- dae）, have rich microbial communities inhabiting the gut, and these bacteria contribute to the fitness of the pest. In this study we ev...Larvae of the diamondback moth, Plutella xylostella L. （Lepidoptera： Plutelli- dae）, have rich microbial communities inhabiting the gut, and these bacteria contribute to the fitness of the pest. In this study we evaluated the effects of five antibiotics （rifampicin, ampicillin, tetracycline, streptomycin sulfate and chloramphenicol） on the gut bacterial di- versity ofP xylostella larvae. We screened five different concentrations for each antibiotic in a leaf disc assay, and found that rifampicin and streptomycin sulfate at 3 mg/mL signif- icantly reduced the diversity of the bacterial community, and some bacterial species could be rapidly eliminated. The number of gut bacteria in the rifampicin group and strepto- mycin sulfate group decreased more rapidly than the others. With the increase of antibiotic concentration, the removal efficiency was improved, whereas toxic effects became more apparent. All antibiotics reduced larval growth and development, and eventually caused high mortality, malformation of the prepupae, and hindered pupation and adult emergence. Among the five antibiotics, tetracycline was the most toxic and streptomycin sulfate was a relatively mild one. Some dominant bacteria were not affected by feeding antibiotics alone. Denaturing gradient gel electrophoresis graph showed that the most abundant and diverse bacteria in P xylostella larval gut appeared in the cabbage feeding group, and diet change and antibiotics intake influenced gut flora abundance. Species diversity was significantly reduced in the artificial diet and antibiotics treatment groups. After feeding on the artificial diet with rifampicin, streptomycin sulfate and their mixture for 10 days, larval gut bacteria could not be completely removed as detected with the agarose gel electrophoresis method.展开更多
There exists a kind of symbiotic bacterium named ＂Candidatus Arsenophonus nilaparvatae＂ in the brown planthopper （BPH）, Nilaparvata lugens. After being filtered and assembled from the BPH genome sequencing project...There exists a kind of symbiotic bacterium named ＂Candidatus Arsenophonus nilaparvatae＂ in the brown planthopper （BPH）, Nilaparvata lugens. After being filtered and assembled from the BPH genome sequencing project, the genome sequence of this bacterial symbiont was obtained. After initial analysis based on the genome, we have found its potential role to synthesize B vitamins for the host. In order to better understand the lifestyle and the genomic changes of this symbiotic bacterium after the symbiotic relationship was established, we further report the characteristics of this draft genome. Compared with several other related bacteria, ＂Candidatus Arsenophonus nilaparvatae＂ has proven to be a facultative endosymbiont at the genomic level. Concurrently, the presence of fimbriae and flagella formation related genes indicates this maternally transmitted endosymbiont is most likely to retain the capacity to invade new hosts. Through further analysis of annotated gene sets, we also find evidence of genome reduction in its secretion system and metabolic pathways. These findings reflect its evolutionary trend to be an obligate one and enable a deeper study of microbe-insect interactions.展开更多
文摘Facultative bacterial endosymbionts in insects have been under intense study during the last years. Endosymbionts can modify the insect＇s phenotype, conferring adap- tive advantages under environmental stress. This seems particularly relevant for a group of worldwide agricultural aphid pests, because endosymbionts modify key fitness-related traits, including host plant use, protection against natural enemies and heat tolerance. Aimed to understand the role of facultative endosymbionts on the success of introduced aphid pests, the distribution and abundance of 5 facultative endosymbionts （Hamiltonella defensa, Regiella insecticola, Serratia symbiotica, Rickettsia and Spiroplasma） were stud- ied and compared in 4 cereal aphids （Sitobion avenae, Diuraphis noxia, Metopolophium dirhodum and Schizaphis graminium） and in the pea aphid Acyrthosiphon pisum complex from 2 agroclimatic zones in Chile. Overall, infections with faeultative endosymbionts exhibited a highly variable and characteristic pattern depending on the aphid species/host race and geographic zone, which could explain the success of aphid pest populations after their introduction. While S. symbiotica and H. defensa were the most frequent endosym- bionts carried by the A. pisum pea-race and A. pisum alfalfa-race aphids, respectively, the most frequent facultative endosymbiont carried by all cereal aphids was R. insecticola. Interestingly, a highly variable composition of endosymbionts carried by S. avenae was also observed between agroclimatic zones, suggesting that endosymbionts are responding differentially to abiotic variables （temperature and precipitations）. In addition, our findings constitute the first report of bacterial endosymbionts in cereal aphid species not screened before, and also the first report of aphid endosymbionts in Chile.
基金We thank Kai-Li Zhang of Institute of Plant Protection,Jiangsu Academy of Agricultural Sciences for help with the collection of B.tabaci populations.This study was supported by the National Natural Science Foundation of China(31701797)the Natural Science Foundation of Jiangsu Province,China(BK20170598)the Key Re-search and Development Program of Jiangsu Province,China(BE2010342).
文摘The maternally heritable endosymbiont provides many ecosystem functions.Antibiotic elimination of a specific symbiont and establishment of experimental host lines lacking certain symbionts enable the roles of a given symbiont to be explored.The whitefly Bemisia tabaci(Gennadius)in China harbors obligate symbiont Portiera infecting each in-dividual,as well as facultative symbionts,such as Hamiltonella,Rickettsia and Cardinium,with co-infections occurring relatively frequently.So far no studies have evaluated the selectivity and efficacy of a specific symbiont elimination using antibiotics in whiteflies co-infected with different symbionts.Furthermore,no success has been achieved in estab-lishing certain symbiont-free B.tabaci lines.In this study,we treated Hamiltonella infected B.tabaci line,Hamiltonella-Rickettsia-co infected line and Hamiltonella-Cardinium co-infected line by feeding B.tabaci adults with cotton plants cultured in water containing ri-fampicin,ampicillin or a mixture of them,aiming to selectively curing symbiont infections and establishing stable symbiont-free lines.We found ampicillin selectively eliminated Cardinium without afecting Portiera,Hamiltonella and Rickettsia,although they coex-isted in the same host body.Meanwhile,all of the symbionts considered in our study can be removed by rifampicin.The reduction of facultative symbionts occurred at a much quicker pace than obligate symbiont Portiera during rifampicin treatment.Also,we measured the stability of symbiont elimination in whitefly successive generations and established Rickettsia-infected and Cardinium-infected lines which are absent in natural populations.Our results provide new protocols for selective elimination of symbionts co-existing in a host and establishment of different symbiont-infected host lines.
文摘Bacterial endosymbionts of sap-sucking insects provide their host with a num- ber of beneficial qualities,including the supply of nutrition,defense against parasitoids, and protection from heat stress.Damage to these bacterial associates can therefore have a negative impact on the fitness of their insect host.We evaluated observational and experi- mental factors regarding the normative hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera:Adelgidae)to help understand the roles of its three recently identified symbionts,including under heat stress conditions.The prevalence of A.tsugae's facultafive symbiont (Serratia symbiotica)was examined at different spatial scales to determine how variable infection rates are for this symbiont.There was no significant difference found in infection rates between adelgids on a tree,within a plot,or within a state.However, significantly more adelgids in Georgia (95%)had S.symbiotica compared to those in New York (68%).Microsatellite genotyping of the adelgids found that this difference was most likely not the result of a second introduction ofA.tsugae into eastern North America.Comparison orS.symbiotica proportions between first and fourth instars showed that symbiont absence did not affect the ability ofA.tsugae to survive aestivation.Evaluations of sym- biont densities within each adelgid found that when S.symbiotica was absent,the density of obligate symbionts was significantly higher.Exposure to heat stress (32.5℃)was not consistently correlated with changes in symbiont densities over a 4-d period.Overall,we have shown that symbiont prevalence and densities vary within the broad population of A.tsugae in eastern North America,with potentially significant effects upon the ecology of this important pest.
基金supported by the National Natural Science Foundation of China(32370471,32070406)Basic and Applied Basic Research Founda-tion of Guangdong Province(2024A1515011110)the Project(No.RSP2025R7)of King Saud University,Saudi Arabia.
文摘Methanogenic endosymbionts are the only known intracellular archaeans and are especially common in anaerobic ciliated protists.Studies on the evolution of associations between anaerobic ciliates and their methanogenic endosymbionts offer an excellent opportunity to broaden our knowledge about symbiosis theory and adaptation of eukaryotes to anoxic environments.Here,the diversity of methanogenic endosymbionts was analyzed with the addition of nine anaerobic ciliate populations that were newly studied by various methods.Results showed that diverse anaerobic ciliates host methanogenic endosymbionts that are limited to a few genera in orders Methanomicrobiales,Methanobacteriales,and Methanosarcinales.For the first time,anaerobic ciliates of the classes Muranotrichea and Prostomatea were found to host methanogenic endosymbionts.Distinct origins of endosymbiosis were revealed for classes Armophorea and Plagiopylea.We posit that armophoreans and plagiopyleans might have harbored Methanoregula(order Methanomicrobiales)and Methanocorpusculum(order Metha-nomicrobiales),respectively,as methanogenic endosymbionts at the beginning of their evolution.Subsequently,independent endosymbiont replacement events occurred in methanogen-ciliate associations,probably due to ecological transitions,species radiation of ciliate hosts,and vertical transmission bottlenecks of endosymbionts.Our results shed light on the evolution of associations between anaerobic ciliates and methanogens,and identifies the necessary preconditions for illustrating mecha-nisms by which endosymbioses between these partners were established.
基金supported by the National Natural Science Foundation of China(31672025,31471765 and 31630057)
文摘The brown planthopper, Nilaparvata lugens St?l, has become a major threat in tropical Asian and China since the rice green revolution of the 1960 s. Currently, insecticide application remains the primary choice for controlling this rice insect pest, but heavy use of insecticides poses dangerous risks to beneficial natural enemies and pollinators, and stimulates N. lugens reproductivity, and has caused a resurgence of the pest in the major rice-planting regions throughout Asia. Achieving the long-lasting goal of sustainable management of N. lugens requires understanding of the molecular basis of outbreaks of the pest and the development of environment-friendly pest-control strategies. Here, we review the recent molecular advances in N. lugens research on the aspects of its endosymbionts, virus transmission, insecticide resistance, and interaction between N. lugens and rice plants. We also put forward further research directions that may shed some lights on management of the rice pest.
文摘The invasive insect pest, red palm weevil (RPW), Rhynchophorus ferrugineus, poses a significant threat to date production, causing substantial economic damage. If uncontrolled, RPW leads the severely infested host tree to collapse and eventually die. The symbiotic associations with microorganisms and RPW in their gut may help their host insects’ establishment, development, nutrition assimilation, and survival. The objective of this research was the molecular characterization of the microbiome of RPW. In this study, the microbiome was compared among different tissues in females and males of RPW of three different morphs and larvae collected from date palm plantations in the Kingdom of Bahrain. A 251-bp segment of bacterial 16S rRNA was amplified by PCR, sequenced, and processed using the bioinformatics platform QIIME2. One ASV, corresponding to the obligate weevil symbiont Nardonella, predominated in adult female samples, constituting 56 ± 7% of total reads, but was less dominant in male samples (12 ± 3%) and larval samples (2.6 ± 1.9%). For females, samples that included reproductive tissues were almost entirely composed of Nardonella (88% - 99%). When Nardonella was excluded from analyses, there were no differences between adult females and adult males, but larval samples were more species-rich and differed in microbial composition from adults. There were no consistent differences in the microbiomes among morphs. Several specimens showed evidence of infection with host-specific strains of Spiroplasma-like members of the Entomoplasmatales, which are often pathogens or vertically transmitted symbionts. Such close microbial associates deserve additional attention as potential routes to control this destructive date palm pest.
基金supported by the National Natural Science Foundation of China (30871631)the Natural Science Foundation of Chongqing, China(2007BB1364)
文摘Pederin belongs to a group of antitumor compounds found in terrestrial beetles and marine sponges. It is apparently used by some members of the rove beetle Paederus as a chemical defense against predators. A recent cluster analysis of the putative pederin biosynthesis gene （ped） strongly suggests that pederin is produced by bacterial symbionts. This paper reviewed the criteria for proving symbiontic origin of bioactive metabolite, indirect and molecular evidences for pederin bacterial origin, as well as three sets ofped clusters and putative biosynthesis process of pederin.
文摘Brasenia schreberi (water shield), a perennial freshwater aquatic plant of the family Nymphaeaceae, is rich in polysaccharides with positive biological activity and potential application value. As an indicator plant of the environment in wetlands, B. schreberi original and wild water environment faced increasing deterioration and has been listed as a critically endangered species in several countries of East Asia. Seeking an alternative method to produce B. schreberi mucilage polysaccharide is of top priority. The morphological structure of the stem and leaf of B. schreberi was studied. Well-developed glandular cells and aerenchyma tissue were observed in the stem and leaves of water shield, which were related to its aquatic habitat and polysaccharide secretion and then three endophytic bacteria were successfully isolated and purified from its stem and leaf and identified as Micromonospora sp. YG-1, Xylariaceae sp. strain UT-X and Psychrobacter pulmonis strain T-15. Symbiotic bacteria from B. schreberi produced polysaccharides with similar spectral peaks and chemical functional groups to those of B. chinensis. Further, analysis of hydroxyl free radicals showed that symbiotic bacteria in water shield had significant antioxidant activity against hydroxyl free radicals. This study provides a theoretical and practical basis for further study using symbiotic bacteria to produce polysaccharides to overcome the environmental limitations of the growth and development of B. schreberi.
基金supported by National Natural Science Fund Project (No.31601890)the Fundamental Research Funds for the Henan Provincial Colleges and Universities in Henan University of Technology (No.2016XTCX01)
文摘Insect symbionts Wolbachia used for pest population control has focused on vector pest species and agricultural insects while rare reports in Chinese stored-product insect samples.In this paper,we surveyed the prevalence of Wolbachia using a PCR detection method in ten Tenebrionidae stored-product insects.Subsequently,the spatiotemporal Wolbachia infection dynamics in Tribolium confusum and Wolbachia elimination patterns using tetracycline treatment were investigated in detail by TaqMan®probe real-time quantitative PCR,and host reproductive fitness parameters were compared.T.confusum was the only Wolbachia infected species in all the surveyed species.Wolbachia infection density consistently increased with the development of T.confusumand plateaued at 3.7×107 wsp copies per individual insect at the young adult stage.Wolbachia densities in females were higher than that in males with a significant difference at the pupae stage and varied among different tissues and organs.Uninfected female beetles were completely incapable of producing mature progenies when crossed with Wolbachia infected males.Embryogenesis and egg hatch rate were specifically inhibited after Wolbachia elimination,while other traits,including the number of eggs,pupation rate and sex ratio,remained unaffected by tetracycline treatment.Our results showthat the TaqMan®probe qPCR is a reliable detection method for quantifying the density of Wolbachia as compared to qualitative detection of wsp gene by PCR and relatively quantified by real-time qPCR.The fitness results indicated that Wolbachia infection was not an obligate symbiont and benefited the host confused flour beetle.
基金funded by the National Basic Research Program of China (973, Grant No. 2010CB126202)the Agro-Industry R & D Special Fund of China (Grant No. 201003031)
文摘The structures of bacterial communities in the brown planthopper （BPH） Nilaparvata lugens （St^l） from different geographic and resistant virulent populations were analyzed by using denatured gradient gel electrophoresis （DGGE）. Results showed that the bacterial communities in BPH nymph from the first to the fifth instars varied with nymphal growth and development. The bacterial communities in the first-instar BPH nymph were similar to those in adults. Nine geographic BPH populations were divided into three groups based on the cluster analysis of DGGE fingerprint. The first group was from the Philippines; the second group was from Thailand and Hainan, Yunnan and Zhejiang provinces of China; and the third group was from Vietnam and Guangxi, Hunan and Jiangxi provinces of China. BPH populations adapted to different resistant rice varieties. The BPH populations from Mudgo （with resistant gene Bphl） and ASD7 （with resistant gene bph2） differed with those of the susceptible rice variety TNI.
基金supported by the Slovak Research and Development Agency under contract No.APVV-19-0076 and No.APVV-23-0015by the Grant Agency of the Ministry of Education,Science,Research and Sport of the Slovak Republic and Slovak Academy of Sciences under the Grant VEGA 1/0013/21.provided by The Ministry of Education,Science,Research and Sport of the Slovak Republic in cooperation with Centre for Scientific and Technical Information of the Slovak Republic.
文摘Astome ciliates live in the digestive tract of a broad spectrum of marine, freshwater, and terricolous annelids. In aquatic lumbriculid and criodrilid oligochaetes collected in Central Europe, we rediscovered three insufficiently known astomes: Hoplitophrya secans, Mesnilella clavata, and Buchneriella criodrili. Their morphology was studied using in vivo observation, protargol, and dry silver nitrate impregnation. Multiple nuclear and mitochondrial molecular markers were used to determine their phylogenetic positions and reconstruct their evolutionary history. According to our phylogenetic analyses: (1) mouthless ciliates isolated from annelids form a robustly supported monophylum within the class Oligohymenophorea, (2) the progenitor of astomes invaded the digestive tract of marine polychaetes during the Paleozoic era, (3) lumbricid earthworms likely served as a source of astomes for criodrilid, almid, and megascolecid earthworms, (4) the ancestral host of the earthworm-dwelling astome clade led an endogeic lifestyle, and (5) there were multiple independent transfers of astomes from endogeic to epigeic and anecic earthworms. These findings support previous views of the annelid phylogeny, suggesting that astomes reside and evolve in tandem with annelids for several hundred million years.
基金funded by the programs of the China Agriculture Research System of MOF and MARA(CARS-02)the Agricultural Science and Technology Innovation Program(ASTIP)of CAAS.
文摘Aphids are sap-feeding plant pests that depend on their symbiotic relationships with the primary endosymbiont Buchnera aphidicola to adapt to impoverished diets. However, how the host plant affects the aphid primary symbiont and aphid adaptation to host plant transfer are poorly known. In this study, aphid symbiont screening and genotype identification were used to establish 2 aphid strains (Rhopalosiphum maidis [Rm] and Rhopalosiphum padi [Rp] strains) containing only Buchnera without any secondary symbionts for both wheat aphid species (R. maidis and R. padi). Aphid fitness and Buchnera titers were unstable on some of these host plants after transferring to novel host plants (G1–G5), which were influenced by host plant species and generations;however, they stabilized after prolonged feeding on the same plants for 10 generations. The electropenetrography (EPG) records showed that the allocation of aphid feeding time was significantly distinct in the 6 host plants;aphids had more intracellular punctures and spent more nonprobing time on green bristlegrass which was not conducive to its growth compared with other plants. The content of soluble sugar, soluble protein, and amino acid in the leaves of the 6 host plants were also clearly separated. The correlation coefficient analysis showed that the nutrient contents of host plants had significant correlations with aphid feeding behaviors, fitness, and Buchnera titers. In the meantime, aphid fitness, and Buchnera titers were also affected by aphid feeding behaviors. Also, Buchnera titers of aphid natural populations on 6 host plants showed a visible difference. Our study deepened our understanding of the interaction among aphids, endosymbionts, and host plants, indicating that the host plant nutrient content is a predominant factor affecting aphid adaptation to their diet, initially affecting aphid feeding behaviors, and further affecting aphid fitness and Buchnera titers, which would further contribute to exploiting new available strategies for aphid control.
基金supported by National Institute of Food and Agriculture(Award No.2010-65106-20675)supported by the National Science Foundation(Award No.IOS-072093 and IOSEAGER-1450331)Bill&Melinda Gates Foundation via a subcontract(B0426×5)from the National Research Institute,University of Greenwich,UK
文摘Hemipteran and dipteran insects have behavioral,cellular and chemical strategies for evading or coping with the host plant defenses making these insects particularly destructive pests worldwide. A critical component of a host plant＇s defense to herbivory is innate immunity. Here we review the status of our understanding of the receptors that contribute to perception of hemipteran and dipteran pests and highlight the gaps in our knowledge in these early events in immune signaling. We also highlight recent advances in identification of the effectors that activate pattern-triggered immunity and those involved in effector-triggered immunity.
文摘Wolbachia can profoundly influence the survival, reproduction, and defenses of insect hosts. These interactions could potentially be harnessed for managing pests or insecttransmitted diseases. Diaphorina citri Kuwayama is a phloem-feeding pest capable of transmitting the putative causal agent of citrus greening, Candidatus Liberibacter asiaticus (CLas). Like many insects, D. citri is also infected with Wolbachia (wDi). Recent studies indicate that the relative abundance of wDi could be associated with the abundance of CLas, and that wDi may contribute to regulating expression of phage lytic cycle genes in CLas, suggesting the need for better understanding of wDi biology in general. This study investigated the genetic diversity of wDi among D. citri in populations spanning eleven countries and two U.S. territories. Six Wolbachia genes, wsp, coxA.fbpA.ftsZ, gatB, and hep A, were sequenced and compared across samples. Two prevalent wDi strains were identified across the samples, and screening of clone libraries revealed possible coinfection of wDi strains in specific populations. D. citri mitochondrial cytochrome oxidase subunit I gene (mtCOI) were more divergent between D. citri populations that were infected with different wDi strains or had different infection statuses (single infection vs. coinfection). While we could not eliminate the possibility that maternal transmission may contribute to such patterns, it is also possible that wDi may induce cytoplasmic incompatibility in their host. These fin dings should contribute to the understanding of wDi population ecology, which may facilitate manipulation of this endosymbiont for management of citrus greening disease worldwide.
文摘Bemisia tabaci-transmitted geminiviruses are one of the major threats on cassava and vegetable crops in Africa. However, to date, few studies are available on the diversity orB. tabaci and their associated endosymbionts in Africa. More than 28 species have been described in the complex ofB. tabaci cryptic species; among them, 2 are invasive pests worldwide： MED and MEAM1. In order to assess the species diversity orB. tabaci in vegetable crops in Senegal, several samplings in different localities, hosts and seasons were collected and analyzed with nuclear （microsatellite） and mitochondrial （COI） markers. The bacterial endosymbiont community was also studied for each sample. Two species were detected： MED Q1 and MEAM1 B. Patterns of MED Q1 （dominance on most of the samples and sites, highest nuclear and mitochondrial diversity and broader secondary endosymbiont community： Hamiltonella, Cardinium, Wolbachia and Rickettsia）, point toward a predominant resident begomovirus vector group for MED Q 1 on market gardening crops. Furthermore, the lower prevalence of the second species MEAM1 B, its lower nuclear and mitochondrial diversity and a narrower secondary endosymbiont community （Hamiltonella/Rickettsia）, indicate that this genetic group is exotic and results from a recent invasion in this area.
基金This work was supported by Texas A&M University and Texas A&M AgriLife Research(Controlling Exotic and Invasive Insect-Transmitted Pathogens)and Hatch project TEX0-1-9381 Accession Number 1015773Xiaotian Tang received the Herb Dean'40 Endowed Scholarship from the Department of Entomology at Texas A&M University.
文摘Immunofluorescence has been widely used to localize microbes or specific molecules in insect tissues or cells.However,significant autofluorescence is frequently observed in tissues which can interfere with the fluorescent identification of target antigens,leading to inaccurate or even false positive fluorescent labeling.The alimentary canal of the potato psyllid,Bactericera cockerelliŠulc,exhibits intense autofluorescence,hindering the application of immunolocalization for the detection and localization of the economically important pathogen transmitted by this insect,“Candidatus Liberibacter solanacearum”(Lso).In the present study,we tested the use of irradiation,hydrogen peroxide(H2O2)and Sudan black B(SBB)treatments to reduce the autofluorescence in the B.cockerelli alimentary canal tissues.Furthermore,we assessed the compatibility of the above‐mentioned treatments with Lso immunolocalization and actin staining using phalloidin.Our results showed that the autofluorescence in the alimentary canal was reduced by irradiation,H2O2,or SBB treatments.The compatibility assays indicated that irradiation and H2O2 treatment both greatly reduced the fluorescent signal associated with Lso and actin.However,the SBB incubation preserved those target signals,while efficiently eliminating autofluorescence in the psyllid alimentary canal.Therefore,herein we propose a robust method for reducing the autofluorescence in the B.cockerelli alimentary canal with SBB treatment,which may improve the use of immunofluorescence labeling in this organism.This method may also have a wide range of uses by reducing the autofluorescence in other arthropod species.
文摘Male-killing is 1 of 4 known strategies that inherited parasitic endosymbionts have evolved to manipulate their host＇s reproduction. In early male-killing, infected male offspring are killed early in embryogenesis. Within the Insecta, male-killing bacteria have been found in a wide range of hosts. The Coccinellidae families of beetles, better known as ladybirds, are particularly prone to male-killer invasion. In samples of the coccinellid, Coc- cinula crotchi, from Japan, a new male-killing bacterium was revealed by phenotypic assay. Molecular genetic analysis revealed the identity to be a tetracycline-sensitive Flavobac- terium that causes female-biased offspring sex ratio. Furthermore, that Flavobacterium strain was found to be closely related to the Flavobacterium causing male-killing in the congeneric Japanese coccinellid, Coccinula sinensis, which was collected from the same region. However, we found slightly different Flavobacterium strains infecting C. sinen- sis from regions with different environmental conditions. This may be an indication of horizontal transmission of male-killing Flavobacterium between these 2 ladybird spices. Finally, environmental conditions may affect the spread of male-killing bacteria among their hosts.
文摘Larvae of the diamondback moth, Plutella xylostella L. （Lepidoptera： Plutelli- dae）, have rich microbial communities inhabiting the gut, and these bacteria contribute to the fitness of the pest. In this study we evaluated the effects of five antibiotics （rifampicin, ampicillin, tetracycline, streptomycin sulfate and chloramphenicol） on the gut bacterial di- versity ofP xylostella larvae. We screened five different concentrations for each antibiotic in a leaf disc assay, and found that rifampicin and streptomycin sulfate at 3 mg/mL signif- icantly reduced the diversity of the bacterial community, and some bacterial species could be rapidly eliminated. The number of gut bacteria in the rifampicin group and strepto- mycin sulfate group decreased more rapidly than the others. With the increase of antibiotic concentration, the removal efficiency was improved, whereas toxic effects became more apparent. All antibiotics reduced larval growth and development, and eventually caused high mortality, malformation of the prepupae, and hindered pupation and adult emergence. Among the five antibiotics, tetracycline was the most toxic and streptomycin sulfate was a relatively mild one. Some dominant bacteria were not affected by feeding antibiotics alone. Denaturing gradient gel electrophoresis graph showed that the most abundant and diverse bacteria in P xylostella larval gut appeared in the cabbage feeding group, and diet change and antibiotics intake influenced gut flora abundance. Species diversity was significantly reduced in the artificial diet and antibiotics treatment groups. After feeding on the artificial diet with rifampicin, streptomycin sulfate and their mixture for 10 days, larval gut bacteria could not be completely removed as detected with the agarose gel electrophoresis method.
基金Acknowledgments This work was supported by grants from the National Natural Science Foundation of China （31272374 and 31070136） and the National Basic Research Program of China （973 Program, No. 2010CB 126205）.
文摘There exists a kind of symbiotic bacterium named ＂Candidatus Arsenophonus nilaparvatae＂ in the brown planthopper （BPH）, Nilaparvata lugens. After being filtered and assembled from the BPH genome sequencing project, the genome sequence of this bacterial symbiont was obtained. After initial analysis based on the genome, we have found its potential role to synthesize B vitamins for the host. In order to better understand the lifestyle and the genomic changes of this symbiotic bacterium after the symbiotic relationship was established, we further report the characteristics of this draft genome. Compared with several other related bacteria, ＂Candidatus Arsenophonus nilaparvatae＂ has proven to be a facultative endosymbiont at the genomic level. Concurrently, the presence of fimbriae and flagella formation related genes indicates this maternally transmitted endosymbiont is most likely to retain the capacity to invade new hosts. Through further analysis of annotated gene sets, we also find evidence of genome reduction in its secretion system and metabolic pathways. These findings reflect its evolutionary trend to be an obligate one and enable a deeper study of microbe-insect interactions.
