Romipeptides A and B(1 and 2),two new romidepsin derivatives,and three known compounds,chromopeptide A(3),romidepsin(4)and valine-leucine dipeptide(5)were isolated from the fermentation broth of Chromobacterium violac...Romipeptides A and B(1 and 2),two new romidepsin derivatives,and three known compounds,chromopeptide A(3),romidepsin(4)and valine-leucine dipeptide(5)were isolated from the fermentation broth of Chromobacterium violaceum No.968.Their structures were elucidated by interpretation of their UV,HR-ESI-MS and NMR spectra.The absolute configuration of compound 1 and 2 were established by single crystal X-ray diffraction analysis.Compounds 1–5 were evaluated for their anti-proliferative activities against three human cancer cell lines,SW620,HL60,and A549.The results showed most of these compounds exhibited antitumor activities in vitro,in which compound 2 displayed potent cytotoxicity to SW620,HL60 and A549 cell lines,with IC_(50) of 12.5,6.7 and 5.7 nmol·L^(–1),respectively.展开更多
Chromobacterium violaceum is a gram-negative bacterium, which has been used widely in microbiology labs involved in quorum sensing(QS) research. Among the QS-regulated traits of this bacterium, violacein production ha...Chromobacterium violaceum is a gram-negative bacterium, which has been used widely in microbiology labs involved in quorum sensing(QS) research. Among the QS-regulated traits of this bacterium, violacein production has received the maximum attention. Violacein production in this organism, however is not under sole control of QS machinery, and other QSregulated traits of this bacterium also need to be investigated in better detail. Though not often involved in human infections, this bacterium is being viewed as an emerging pathogen. This review attempts to highlight the recent research advances on Chromobacterium violaceum, with respect to violacein biosynthesis, development of various applications of this bacterium and its bioactive metabolite violacein, and its pathogenicity.展开更多
Objective:To investigated into the anti-quorum sensing(QS)activity of Syzygium cumini L.(S.cumini)and Pimenta dioica L.(P.dioica)using Chromobacterium violaceum(C.violaceum)strains.Methods:In this study,anti-QS activi...Objective:To investigated into the anti-quorum sensing(QS)activity of Syzygium cumini L.(S.cumini)and Pimenta dioica L.(P.dioica)using Chromobacterium violaceum(C.violaceum)strains.Methods:In this study,anti-QS activity of ethanol extract of Syzygium cumini L.and Pimenta dioica L.were screened using C.violaceum CV026 biosensor bioassay.By bioassay guided fractionation of 5.cumini and P.dioica,ethyl acetate fraction(EAF)with strong anti-QS activity was separated.Inhibition of QS regulated violacein production in C.violaceum ATCC12472 by EAF was assessed at different concentrations.The effect of EAF on the synthesis of autoinducer like N-acyl homoserine lactone(AHL)was studied in C.violaceum ATCC31532 using its mutant C.violaceum CV026 by standard methods.Results:EAF inhibited violacein production in C.violaceum ATCC12472 in a concentration dependent manner without significant reduction in bacterial growth.Complete inhibition of violacein production was evidenced in 0.75-1.0 mg/mL concentration of EAF without inhibiting the synthesis of the AHL.TLC biosensor overlay profile of EAF revealed two translucent spots in 5.cumini and P.dioica that inhibited C_6-AHL mediated violacein production in C.violaceum CV026.Conclusions:This study indicates the anti-QS activity of the tested medicinal plants against C.violaceum.展开更多
Piericidin A1, 3’-rhamnopiericidin A1, and a novel compound piericidin E, a new quorum-sensing (QS) inhibitor against Chromobacterium violaceum CV026, were isolated from the culture broth of Streptomyces sp. QS is we...Piericidin A1, 3’-rhamnopiericidin A1, and a novel compound piericidin E, a new quorum-sensing (QS) inhibitor against Chromobacterium violaceum CV026, were isolated from the culture broth of Streptomyces sp. QS is well known as a microbial signaling system and controls certain types of gene expression resulting in bioluminescence, biofilm formation, swarming motility, antibiotic biosynthesis, and virulence factor production. C. violaceum CV026 is commonly used to determine qualitative and quantitative QS activity. The structures of piericidin derivatives were characterized, and their QS activities were determined.展开更多
Background: Chromobacterium violaceum is a Gram-negative, a facultative anaerobe bacteria producing violacein pigment. C. violaceum is generally present as the normal flora of water and soil. The Urine Tract Infection...Background: Chromobacterium violaceum is a Gram-negative, a facultative anaerobe bacteria producing violacein pigment. C. violaceum is generally present as the normal flora of water and soil. The Urine Tract Infection (UTI) due to C. violaceum is very rare. Until now there was no report from Africa about UTIs caused by C. violaceum. The antimicrobial susceptibility pattern of C. violaceum is very limited due to the rarity of isolation from clinical specimens. Here, we describe the first case of urinary tract infection caused by C. violaceum in Angola. Aim: Our case report was carried out to assess the sensitivity and resistance pattern of C. violaceum as the causative agent of UTI. Results: C. violaceum was sensitive to Amoxicillin/Clavulanic acid, Ceftriaxon, Ciprofloxacin, Doxycycline, Trimethoprim/Sulfamethoxazole, Piperacilin/Tazobactam, Gentamicin, Amikacin, Aztreonam and imipenem. The bacteria showed resistance to Cefuroxime. Conclusion: Here, we report a rare case of complicate urinary tract infection caused by C. violaceum in patient, who was treated successfully with ciprofloxacin for a total duration of 7 days.展开更多
Chromobacterium violaceum is a Gram negative, facultative anaerobe, generally present in water, soil in tropical and subtropical regions. This bacterium is an emerging environmental pathogen that causes life threateni...Chromobacterium violaceum is a Gram negative, facultative anaerobe, generally present in water, soil in tropical and subtropical regions. This bacterium is an emerging environmental pathogen that causes life threatening infection in humans and animals. It can cause wound infection, visceral abscess, septicaemia, meningitis, diarrhoea, UTI. It is associated with significant mortality due to severe systemic infection. As the bacteria have high spreading tendency leading to sepsis, early identification and prompt treatment is necessary. Here we report a case of Chromobacterium violaceum wound infection in a 9 years old male from Dhaka, who was successfully treated with combination of cefixime and flucloxacillin antibiotics as per culture sensitivity report.展开更多
Insect-bacteria associations can influence vector competence in multiple ways. Chromobacterium anophelis, a bacterium known to be pathogenic to mosquitoes, may also act as an anti-pathogen by inhibiting the developmen...Insect-bacteria associations can influence vector competence in multiple ways. Chromobacterium anophelis, a bacterium known to be pathogenic to mosquitoes, may also act as an anti-pathogen by inhibiting the development of other pathogens within mosquitoes. The mechanism behind this inhibition remains unclear, with two hypotheses: the bacterium either boosts the mosquito’s immunity or directly targets other pathogens within the mosquito. The objective of this study is to elucidate the mechanism behind this pathogen-inhibition effect in mosquitoes. Bioassays (assessing longevity, fecundity, and fertility) were conducted on mosquitoes infected with the bacterium and an entomopathogenic fungus, Metarhizium pingshaense, whose hyphae grow on mosquitoes after killing them. The prevalence of hyphal growth was evaluated. The longevity of mosquitoes co-infected with Chromobacterium anophelis and Metarhizium pingshaense was significantly higher than those infected solely with the more virulent microorganism, which was Chromobacterium anophelis. Hyphae were observed on 100% of mosquitoes infected only with the fungus, whereas mosquitoes co-infected with the bacterium exhibited a lower prevalence of fungal hyphal growth. The number of eggs laid by infected mosquitoes was approximately the same, within the typical range (50 - 150). However, the number of larvae observed from co-infected mosquitoes was significantly higher than those produced by mosquitoes exposed to the microorganism that most reduced egg hatch rates. These results align with the hypothesis that Chromobacterium anophelis inhibits the development of other pathogens within mosquitoes by directly targeting them.展开更多
Introduction:Chromobacterium haemolyticum(C.haemolyticum)can cause invasive infections in humans.This study aims to reveal the genomic characteristics of C.haemolyticum and provide guidance for clinical diagnosis,trea...Introduction:Chromobacterium haemolyticum(C.haemolyticum)can cause invasive infections in humans.This study aims to reveal the genomic characteristics of C.haemolyticum and provide guidance for clinical diagnosis,treatment,prevention,and control.Methods:Species identification was performed through isolation culture and matrix-assisted laser desorption ionization time-of-flight mass spectrometry.Antibiotic susceptibility testing determined resistance phenotypes.High-throughput sequencing and bioinformatics methods were used to predict antibiotic resistance genes and virulence genes and to analyze the evolutionary characteristics of global C.hemolyticus genomes.Results:In this study,a C.haemolyticum strain was isolated from the bronchoalveolar lavage fluid of a patient in Guangxi Zhuang Autonomous Region,China.The isolate was sensitive to chloramphenicol,macrolides,and trimethoprim,while resistant to betalactams.Comparative genomics analysis revealed that most global strains carry carbapenemase-encoding genes.Phylogenetic analysis showed that the strain from this patient was closely related to a pond-derived C.haemolyticum isolate from Yangzhou,China.Conclusions:This study uncovered the genetic characteristics of C.haemolyticum from various sources worldwide,including antibiotic resistance and virulence factors,providing an important reference for clinical treatment.展开更多
Violacein,a therapeutic pigment synthesised naturally in specific bacterial systems,is commercially unexplored owing to low titers.The current study aimed to formulate a suitable medium and to develop a fed-batch stra...Violacein,a therapeutic pigment synthesised naturally in specific bacterial systems,is commercially unexplored owing to low titers.The current study aimed to formulate a suitable medium and to develop a fed-batch strategy for improving the violacein productivity in a natural producer-Chromobacterium violaceum MTCC2656.The carbon and the nitrogen sources were extensively screened and their levels were optimised for maximal violacein production.The micronutrients in the medium were subjected to a two-level statistical optimisation using design of experiment approach and the final media formulation was validated.As a fed-batch approach,a combination of pulse feeding of glucose and tryptophan with optimised broth harvest of 60%(v/v)was attempted that achieved a titer of 1046±16 mg/L with productivity of 26.12±0.64 mg/L/h in each progressive cycle of fed-batch.The strategic sequential step of media formulation and fed-batch fermentation improved the violacein titer by~5 folds.Kinetic modelling was used to understand the enhancement in fermentation performance in both the batch and fed-batch processes.The findings from the current study would enable to understand and correlate the patterns of substrate uptake and violacein formation to establish strategies for enhancing overall productivity in the fermentation processes.展开更多
A bicyclic depsipeptide, chromopeptide A(1), was isolated from a deep-sea-derived bacterium Chromobacterium sp. HS-13-94. Its structure was determined by extensive spectroscopic analysis and by comparison with a relat...A bicyclic depsipeptide, chromopeptide A(1), was isolated from a deep-sea-derived bacterium Chromobacterium sp. HS-13-94. Its structure was determined by extensive spectroscopic analysis and by comparison with a related known compound. The absolute configuration of chromopeptide A was established by X-ray diffraction analysis employing graphite monochromated Mo K_α radiation(λ ? 0.71073 ?) with small Flack parameter 0.03. Chromopeptide A suppressed the proliferation of HL-60, K-562, and Ramos cells with average IC_(50) values of 7.7, 7.0, and 16.5 nmol/L, respectively.展开更多
In this study,we used accelerated solvent extraction(ASE)to extract flavonoids and anthocyanins from dried red onion peels,producing red onion peel extract(ROPE).High-performance liquid chromatography analysis of ROPE...In this study,we used accelerated solvent extraction(ASE)to extract flavonoids and anthocyanins from dried red onion peels,producing red onion peel extract(ROPE).High-performance liquid chromatography analysis of ROPE obtained using ASE identified important flavonols and anthocyanins.Total flavonoid and anthocyanin contents measured from ROPE were 459.15 mg/g±16.45(DW)and 33.14 mg/g±0.99(DW),respectively.ROPE antimicrobial activity against L.monocytogenes showed strain-specific effects,where the minimum inhibitory concentration(MIC)for V7 was two-fold greater than for EGD and Scott A(i.e.,25.82 vs.12.91 mg quercetin-3,4′-diglucoside equivalents/gram[mg QdGE/g]ROPE).ROPE significantly inhibited(P<0.05)biofilm formation by all three strains at sub-inhibitory concentrations(0.40-6.45 mg QdGE/g)in a concentration-dependent manner.Pre-formed biofilms of mixed L.monocytogenes strains on stainless steel were inactivated after 48 h at 22℃ only with higher concentrations of ROPE(25.82-56.63 mg QdGE/g).Sub-inhibitory concentrations of ROPE also inhibited L.monocytogenes motility and suppressed violacein pigment production in Chromobacterium violaceum ATCC 12472,suggesting that ROPE inhibited quorum sensing.Therefore,our data indicate that red onion peel waste has potential as a source of natural antibacterial compounds as an approach to food safety in the circular economy.展开更多
The effectiveness of current control measures against Aedes mosquitoes remains low, resulting in persistent epidemics in urban areas. The emergence of resistant mosquito populations to chemical insecticides highlights...The effectiveness of current control measures against Aedes mosquitoes remains low, resulting in persistent epidemics in urban areas. The emergence of resistant mosquito populations to chemical insecticides highlights the need for novel, environmentally friendly, cost-effective control strategies. This study explored the potential of environmental bacterial isolates to biocontrol wild Aedes larvae. Initially, we collected bacterial samples from infectious masses of Aedes fluviatilis larvae. The isolated bacteria were identified using biochemical, enzymatic, and molecular methods, including 16S rRNA sequencing and MALDI-TOF. Previously, Aeromonas hydrophila and Bacillus thuringiensis isolated from these infectious masses showed limited Aedes larval inhibition. Consequently, we screened additional environmental isolates from the bacteriotheque. Six isolates previously identified were tested: Chromobacterium violaceum, Enterobacter cloacae, Bacillus cereus, Bacillus sphaericus, and two strains of Bacillus thuringiensis israelensis. Among these strains, B. thuringiensis and C. violaceum exhibited significant inhibitory activities against wild Aedes larvae. Bacillus thuringiensis cultures grown under daylight conditions showed a slight ability to inhibit Aedes larvae. The potential of B. thuringiensis and C. violaceum strains studied, along with optimized culture growth conditions, will be further investigated to develop bioinsecticide products to provide safer and more sustainable alternatives for controlling larvae of Aedes mosquitoes.展开更多
文摘Romipeptides A and B(1 and 2),two new romidepsin derivatives,and three known compounds,chromopeptide A(3),romidepsin(4)and valine-leucine dipeptide(5)were isolated from the fermentation broth of Chromobacterium violaceum No.968.Their structures were elucidated by interpretation of their UV,HR-ESI-MS and NMR spectra.The absolute configuration of compound 1 and 2 were established by single crystal X-ray diffraction analysis.Compounds 1–5 were evaluated for their anti-proliferative activities against three human cancer cell lines,SW620,HL60,and A549.The results showed most of these compounds exhibited antitumor activities in vitro,in which compound 2 displayed potent cytotoxicity to SW620,HL60 and A549 cell lines,with IC_(50) of 12.5,6.7 and 5.7 nmol·L^(–1),respectively.
文摘Chromobacterium violaceum is a gram-negative bacterium, which has been used widely in microbiology labs involved in quorum sensing(QS) research. Among the QS-regulated traits of this bacterium, violacein production has received the maximum attention. Violacein production in this organism, however is not under sole control of QS machinery, and other QSregulated traits of this bacterium also need to be investigated in better detail. Though not often involved in human infections, this bacterium is being viewed as an emerging pathogen. This review attempts to highlight the recent research advances on Chromobacterium violaceum, with respect to violacein biosynthesis, development of various applications of this bacterium and its bioactive metabolite violacein, and its pathogenicity.
基金Supported by the Department of Biotechnology.Govt.of India,under Rapid Grant for Young Investigator scheme(Grant no.BT/PR13242/CBD/27/226/2009)
文摘Objective:To investigated into the anti-quorum sensing(QS)activity of Syzygium cumini L.(S.cumini)and Pimenta dioica L.(P.dioica)using Chromobacterium violaceum(C.violaceum)strains.Methods:In this study,anti-QS activity of ethanol extract of Syzygium cumini L.and Pimenta dioica L.were screened using C.violaceum CV026 biosensor bioassay.By bioassay guided fractionation of 5.cumini and P.dioica,ethyl acetate fraction(EAF)with strong anti-QS activity was separated.Inhibition of QS regulated violacein production in C.violaceum ATCC12472 by EAF was assessed at different concentrations.The effect of EAF on the synthesis of autoinducer like N-acyl homoserine lactone(AHL)was studied in C.violaceum ATCC31532 using its mutant C.violaceum CV026 by standard methods.Results:EAF inhibited violacein production in C.violaceum ATCC12472 in a concentration dependent manner without significant reduction in bacterial growth.Complete inhibition of violacein production was evidenced in 0.75-1.0 mg/mL concentration of EAF without inhibiting the synthesis of the AHL.TLC biosensor overlay profile of EAF revealed two translucent spots in 5.cumini and P.dioica that inhibited C_6-AHL mediated violacein production in C.violaceum CV026.Conclusions:This study indicates the anti-QS activity of the tested medicinal plants against C.violaceum.
文摘Piericidin A1, 3’-rhamnopiericidin A1, and a novel compound piericidin E, a new quorum-sensing (QS) inhibitor against Chromobacterium violaceum CV026, were isolated from the culture broth of Streptomyces sp. QS is well known as a microbial signaling system and controls certain types of gene expression resulting in bioluminescence, biofilm formation, swarming motility, antibiotic biosynthesis, and virulence factor production. C. violaceum CV026 is commonly used to determine qualitative and quantitative QS activity. The structures of piericidin derivatives were characterized, and their QS activities were determined.
文摘Background: Chromobacterium violaceum is a Gram-negative, a facultative anaerobe bacteria producing violacein pigment. C. violaceum is generally present as the normal flora of water and soil. The Urine Tract Infection (UTI) due to C. violaceum is very rare. Until now there was no report from Africa about UTIs caused by C. violaceum. The antimicrobial susceptibility pattern of C. violaceum is very limited due to the rarity of isolation from clinical specimens. Here, we describe the first case of urinary tract infection caused by C. violaceum in Angola. Aim: Our case report was carried out to assess the sensitivity and resistance pattern of C. violaceum as the causative agent of UTI. Results: C. violaceum was sensitive to Amoxicillin/Clavulanic acid, Ceftriaxon, Ciprofloxacin, Doxycycline, Trimethoprim/Sulfamethoxazole, Piperacilin/Tazobactam, Gentamicin, Amikacin, Aztreonam and imipenem. The bacteria showed resistance to Cefuroxime. Conclusion: Here, we report a rare case of complicate urinary tract infection caused by C. violaceum in patient, who was treated successfully with ciprofloxacin for a total duration of 7 days.
文摘Chromobacterium violaceum is a Gram negative, facultative anaerobe, generally present in water, soil in tropical and subtropical regions. This bacterium is an emerging environmental pathogen that causes life threatening infection in humans and animals. It can cause wound infection, visceral abscess, septicaemia, meningitis, diarrhoea, UTI. It is associated with significant mortality due to severe systemic infection. As the bacteria have high spreading tendency leading to sepsis, early identification and prompt treatment is necessary. Here we report a case of Chromobacterium violaceum wound infection in a 9 years old male from Dhaka, who was successfully treated with combination of cefixime and flucloxacillin antibiotics as per culture sensitivity report.
文摘Insect-bacteria associations can influence vector competence in multiple ways. Chromobacterium anophelis, a bacterium known to be pathogenic to mosquitoes, may also act as an anti-pathogen by inhibiting the development of other pathogens within mosquitoes. The mechanism behind this inhibition remains unclear, with two hypotheses: the bacterium either boosts the mosquito’s immunity or directly targets other pathogens within the mosquito. The objective of this study is to elucidate the mechanism behind this pathogen-inhibition effect in mosquitoes. Bioassays (assessing longevity, fecundity, and fertility) were conducted on mosquitoes infected with the bacterium and an entomopathogenic fungus, Metarhizium pingshaense, whose hyphae grow on mosquitoes after killing them. The prevalence of hyphal growth was evaluated. The longevity of mosquitoes co-infected with Chromobacterium anophelis and Metarhizium pingshaense was significantly higher than those infected solely with the more virulent microorganism, which was Chromobacterium anophelis. Hyphae were observed on 100% of mosquitoes infected only with the fungus, whereas mosquitoes co-infected with the bacterium exhibited a lower prevalence of fungal hyphal growth. The number of eggs laid by infected mosquitoes was approximately the same, within the typical range (50 - 150). However, the number of larvae observed from co-infected mosquitoes was significantly higher than those produced by mosquitoes exposed to the microorganism that most reduced egg hatch rates. These results align with the hypothesis that Chromobacterium anophelis inhibits the development of other pathogens within mosquitoes by directly targeting them.
基金Supported by grants from the National Key Research and Development Program of China(2023YFC2307101)the Young TopNotch Talents Foundation of Henan Agricultural University(30501278)Project for Young Scientist of the Joint Funds of Science and Technology Research and Development Plan of Henan Province,China(235200810058).
文摘Introduction:Chromobacterium haemolyticum(C.haemolyticum)can cause invasive infections in humans.This study aims to reveal the genomic characteristics of C.haemolyticum and provide guidance for clinical diagnosis,treatment,prevention,and control.Methods:Species identification was performed through isolation culture and matrix-assisted laser desorption ionization time-of-flight mass spectrometry.Antibiotic susceptibility testing determined resistance phenotypes.High-throughput sequencing and bioinformatics methods were used to predict antibiotic resistance genes and virulence genes and to analyze the evolutionary characteristics of global C.hemolyticus genomes.Results:In this study,a C.haemolyticum strain was isolated from the bronchoalveolar lavage fluid of a patient in Guangxi Zhuang Autonomous Region,China.The isolate was sensitive to chloramphenicol,macrolides,and trimethoprim,while resistant to betalactams.Comparative genomics analysis revealed that most global strains carry carbapenemase-encoding genes.Phylogenetic analysis showed that the strain from this patient was closely related to a pond-derived C.haemolyticum isolate from Yangzhou,China.Conclusions:This study uncovered the genetic characteristics of C.haemolyticum from various sources worldwide,including antibiotic resistance and virulence factors,providing an important reference for clinical treatment.
基金funded by the All-India Council of Technical Education,New Delhi,India。
文摘Violacein,a therapeutic pigment synthesised naturally in specific bacterial systems,is commercially unexplored owing to low titers.The current study aimed to formulate a suitable medium and to develop a fed-batch strategy for improving the violacein productivity in a natural producer-Chromobacterium violaceum MTCC2656.The carbon and the nitrogen sources were extensively screened and their levels were optimised for maximal violacein production.The micronutrients in the medium were subjected to a two-level statistical optimisation using design of experiment approach and the final media formulation was validated.As a fed-batch approach,a combination of pulse feeding of glucose and tryptophan with optimised broth harvest of 60%(v/v)was attempted that achieved a titer of 1046±16 mg/L with productivity of 26.12±0.64 mg/L/h in each progressive cycle of fed-batch.The strategic sequential step of media formulation and fed-batch fermentation improved the violacein titer by~5 folds.Kinetic modelling was used to understand the enhancement in fermentation performance in both the batch and fed-batch processes.The findings from the current study would enable to understand and correlate the patterns of substrate uptake and violacein formation to establish strategies for enhancing overall productivity in the fermentation processes.
基金financially supported by the National Marine ‘863’ Project (Nos. 2012AA092105 and 2013AA092902)the National Natural Science Foundation of China (No. 81273430)
文摘A bicyclic depsipeptide, chromopeptide A(1), was isolated from a deep-sea-derived bacterium Chromobacterium sp. HS-13-94. Its structure was determined by extensive spectroscopic analysis and by comparison with a related known compound. The absolute configuration of chromopeptide A was established by X-ray diffraction analysis employing graphite monochromated Mo K_α radiation(λ ? 0.71073 ?) with small Flack parameter 0.03. Chromopeptide A suppressed the proliferation of HL-60, K-562, and Ramos cells with average IC_(50) values of 7.7, 7.0, and 16.5 nmol/L, respectively.
基金supported by the USDA-NIFA-SCRI-2017-51181-26834 through the National Center of Excellence for Melon at the Vegetable and Fruit Improvement Center of Texas A&M University,College Station,Texas and also Institute of Advancing Health through Agriculture.
文摘In this study,we used accelerated solvent extraction(ASE)to extract flavonoids and anthocyanins from dried red onion peels,producing red onion peel extract(ROPE).High-performance liquid chromatography analysis of ROPE obtained using ASE identified important flavonols and anthocyanins.Total flavonoid and anthocyanin contents measured from ROPE were 459.15 mg/g±16.45(DW)and 33.14 mg/g±0.99(DW),respectively.ROPE antimicrobial activity against L.monocytogenes showed strain-specific effects,where the minimum inhibitory concentration(MIC)for V7 was two-fold greater than for EGD and Scott A(i.e.,25.82 vs.12.91 mg quercetin-3,4′-diglucoside equivalents/gram[mg QdGE/g]ROPE).ROPE significantly inhibited(P<0.05)biofilm formation by all three strains at sub-inhibitory concentrations(0.40-6.45 mg QdGE/g)in a concentration-dependent manner.Pre-formed biofilms of mixed L.monocytogenes strains on stainless steel were inactivated after 48 h at 22℃ only with higher concentrations of ROPE(25.82-56.63 mg QdGE/g).Sub-inhibitory concentrations of ROPE also inhibited L.monocytogenes motility and suppressed violacein pigment production in Chromobacterium violaceum ATCC 12472,suggesting that ROPE inhibited quorum sensing.Therefore,our data indicate that red onion peel waste has potential as a source of natural antibacterial compounds as an approach to food safety in the circular economy.
文摘The effectiveness of current control measures against Aedes mosquitoes remains low, resulting in persistent epidemics in urban areas. The emergence of resistant mosquito populations to chemical insecticides highlights the need for novel, environmentally friendly, cost-effective control strategies. This study explored the potential of environmental bacterial isolates to biocontrol wild Aedes larvae. Initially, we collected bacterial samples from infectious masses of Aedes fluviatilis larvae. The isolated bacteria were identified using biochemical, enzymatic, and molecular methods, including 16S rRNA sequencing and MALDI-TOF. Previously, Aeromonas hydrophila and Bacillus thuringiensis isolated from these infectious masses showed limited Aedes larval inhibition. Consequently, we screened additional environmental isolates from the bacteriotheque. Six isolates previously identified were tested: Chromobacterium violaceum, Enterobacter cloacae, Bacillus cereus, Bacillus sphaericus, and two strains of Bacillus thuringiensis israelensis. Among these strains, B. thuringiensis and C. violaceum exhibited significant inhibitory activities against wild Aedes larvae. Bacillus thuringiensis cultures grown under daylight conditions showed a slight ability to inhibit Aedes larvae. The potential of B. thuringiensis and C. violaceum strains studied, along with optimized culture growth conditions, will be further investigated to develop bioinsecticide products to provide safer and more sustainable alternatives for controlling larvae of Aedes mosquitoes.
