Perchlorate(ClO_(4)^(−))is a type of novel persistent inorganic pollutant that has gained increasing attention because of its high solubility,poor degradability,and widespread distribution.However,the impacts of perch...Perchlorate(ClO_(4)^(−))is a type of novel persistent inorganic pollutant that has gained increasing attention because of its high solubility,poor degradability,and widespread distribution.However,the impacts of perchlorate on aquatic autotrophs such cyanobacterium are still unclear.Herein,Synechocystis sp.PCC6803(Synechocystis)was used to investigate the response mechanisms of perchlorate on cyanobacterium by integrating physiological and transcriptome analyses.Physiological results showed that perchlorate mainly damaged the photosystem of Synechocystis,and the inhibition degree of photosystem II(PSII)was severer than that of photosystem I(PSI).When the exposed cells were moved to a clean medium,the photosynthetic activities were slightly repaired but still lower than in the control group,indicating irreversible damage.Furthermore,perchlorate also destroyed the cellular ultrastructure and induced oxidative stress in Synechocystis.The antioxidant glutathione(GSH)content and the superoxide dismutase(SOD)enzyme activity were enhanced to scavenge harmful reactive oxygen(ROS)in Synechocystis.Transcriptome analysis revealed that the genes associated with“photosynthesis”and“electron transport”were significantly regulated.For instance,most genes related to PSI(e.g.,psaf,psaJ)and the“electron transport chain”were upregulated,whereas most genes related to PSII(e.g.,psbA3,psbD1,psbB,and psbC)were downregulated.Additionally,perchlorate also induced the expression of genes related to the antioxidant system(sod2,gpx,gst,katG,and gshB)to reduce oxidative damage.Overall,this study is the first to investigate the impacts andmechanisms of cyanobacterium under perchlorate stress,which is conducive to assessing the risk of perchlorate in aquatic environments.展开更多
The agp gene encoding the ADP-glucose pyrophosphorylase involved in cyanobacterial glycogen synthesis was amplified by PCR. The resulting agp fragment was cloned in plasmid pUC118 to generate plasmid pUCA. Part of the...The agp gene encoding the ADP-glucose pyrophosphorylase involved in cyanobacterial glycogen synthesis was amplified by PCR. The resulting agp fragment was cloned in plasmid pUC118 to generate plasmid pUCA. Part of the fragment within the agp DNA was deleted and replaced by an erythromycin resistance cassette to generate plasmid pUCAE, which was used to transform the Synechocystis sp. PCC 6803 wild-type strain and a mutant with resistance to erythromycin was obtained. PCR analysis of the genomic DNA from the resulting mutant indicated that the appropriate deletion and insertion indeed had occurred. The cell growth and Chl a, glycogen content in the mutant showed difference from those in the wild-type strain. The obtained biomass as well as the Chl a content in the mutant strain was higher than that of the wild-type strain, which suggested that the photosynthesis efficiency in the agp(-) strain was higher than that in the wild-type strain. No glycogen was found in the mutant, providing evidence for the correction of the mutant in physiological level.展开更多
Compositions of glycerolipids and fatty acid compositions of glycerolipids were compared among Synechocystis sp. PCC 6803 cells grown in the BG-11 medium containing different concentrations of glucose and Na2S2O3 in t...Compositions of glycerolipids and fatty acid compositions of glycerolipids were compared among Synechocystis sp. PCC 6803 cells grown in the BG-11 medium containing different concentrations of glucose and Na2S2O3 in this study. It was found that Na2S2O3 can effectively increase the percentage of sulphoquinovosyl diacylglycerol (SQDG) and phosphatidylglycerol (PG) to total membrane lipids and the simultaneous application of glucose with Na2S2O3 can counteract the effect of Na2S2O3. In addition, Na2S2O3 can significantly increase the percentage of palmitic acid (C, 16:0) in fatty acid composition of monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) and decrease the fatty acid unsaturation degree accordingly, and these effects can also be eliminated by glucose. These results indicate that Na2S2O3 can take as a reductant to make membrane lipids in a low unsaturated state, and the simultaneous application of glucose can decrease the reducing power of Na2S2O3. In addition, Na2S2O3 can take as a sulfur donor for the synthesis of SQDG.展开更多
Calcium carbonate （CaCO3） crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 （inoculated BG11）. In this study, the features of calcium carbonate d...Calcium carbonate （CaCO3） crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 （inoculated BG11）. In this study, the features of calcium carbonate deposition were investigated. Inoculated BGll in different calcium ion concentrations was used for the experimental group, while the BGll culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium （Ca）, carbon （C）, oxygen （O）, phosphorus （P）, iron （Fe）, copper （Cu）, zinc （Zn）, and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BGll culture media. There may be more calcium- containing crystals inside and outside of these cells. These results shall be beneficial for understanding the formation mechanism of carbonate minerals.展开更多
In order to explore the mechanism of acute toxicity for pyrene to cyanobacterial organisms, the responses of Synechocystis sp. PCC 6803 photosystem Ⅱ （PS Ⅱ） under pyrene stress were studied. The results showed the...In order to explore the mechanism of acute toxicity for pyrene to cyanobacterial organisms, the responses of Synechocystis sp. PCC 6803 photosystem Ⅱ （PS Ⅱ） under pyrene stress were studied. The results showed there was no significant difference about the oxygen evolution under 0.125 mg/L pyrene stress when compared with control, but it was significantly lower than control at 0.625 mg/L pyrene. Polyphasic chlorophyll-a fluorescence transients in cells of Synechocystis sp. PCC 6803 exhibited a typical increase including O, J, I, and P phases. Fluorescence yield at phases J, I and P declined slightly at 0.125 and 0.625 mg/L pyrene, and significantly lower than control at 3.125 mg/L. According to the parameters deviated from JIP-test, no modification was induced by pyrene both at the donor side and at the acceptor side of PS Ⅱ, and the reaction centre of PS Ⅱ is the primary damaging target. Based on the expressing of four key genes （psbA, psbB, psbC and psbO） of PS Ⅱ, only psbA showed significant difference at 3.125 mg/L pyrene when compared with control.展开更多
The unicellular cyanobacterium Synechocystis sp. PCC 6803, a model organism known for its unique combination of highly desirable molecular genetic, physiological and morphological characteristics, was employed in the ...The unicellular cyanobacterium Synechocystis sp. PCC 6803, a model organism known for its unique combination of highly desirable molecular genetic, physiological and morphological characteristics, was employed in the present study. The species was cultured in BG11 liquid medium contained various initial concentrations of Pb^2＋ and Cd〉 （0, 0.5, 1, 2, 4, 6 and 8 mg/L）. The experiment was conducted for six days and the metal induced alterations in the ultrastructure, growth and pigment contents were assessed. Alterations in the ultrastructure of the Synechocystis sp. PCC 6803 cells became evident with the increased （〉4 mg/L Pb^2＋） metal concentration. The photosynthetic apparatus （thylakoid membranes） were found to be the worst affected. Deteriorated or completely destroyed thylakoid membranes have made large empty spaces in the cell interior. In addition, at the highest concentration （8 mg/L pb^2＋）, the polyphosphate granules became more prominent both in size and number. Despite the initial slight stimulations （0.2, 3.8 and 6.5% respectively at 0.5, 1 and 2 mg/L pb^2＋）, both metals inhibited the growth in a dose-dependent manner as incubation progressed. Pigment contents （chlorophyll a, 13 carotene and phycocyanin） were also decreased with increasing metal concentration. Cells exposed to 6 mg/L Pb^2＋, resulted in 36.56, 37.39 and 29.34% reductions of chlorophyll a, 13 carotene and phycocyanin respectively over the control. Corresponding reductions for the same CdZ＋concentrations were 57.83, 48.94 and 56.90%. Lethal concentration （96 h LC50） values （3.47 mg/L Cd^2＋ and 12.11 mg/L Pb^2＋） indicated that Synechocystis sp. PCC 6803 is more vulnerable to Cd^2＋ than Pb^2＋.展开更多
Synechocystis sp. PCC 6803 is a model organism widely used in cyanobacterium biology and biotechnology. To know the genetic background of substrains of Synechocystis sp. PCC 6803 is important for further research and ...Synechocystis sp. PCC 6803 is a model organism widely used in cyanobacterium biology and biotechnology. To know the genetic background of substrains of Synechocystis sp. PCC 6803 is important for further research and application. In this study, we reported the genome sequences of two non-motile wild-type substrains of Synechocystis sp. PCC 6803 using whole genome resequencing. 55/56 putative single nucleotide polymorphisms(SNPs) and 8/9 Indels(insertion and deletion) were identified. Among these, 47 SNPs were found in both the GT-AR and GT-CH strains, and 8 were unique to GT-AR and 9 were unique to GT-CH. All of these variations were annotated in metabolism pathway referred to KEGG database. Meanwhile, the deletion in s lr0332 gene was detected in these two strains, which attributed to the non-motile phenotype of them and suggested that the insertion in spkA gene was not essential for non-motile phenotype. These resequencing data provide the genetic background information of these two strains and highlighted the microevolution over decades of laboratory cultivation.展开更多
Hemolysin produced by various bacteria,may destroy erythrocyte membranes via a pore-forming mechanism,a deter-gent action,or a lipase activity.Previous to this experiment,the mode of action used by cyanobacterial hemo...Hemolysin produced by various bacteria,may destroy erythrocyte membranes via a pore-forming mechanism,a deter-gent action,or a lipase activity.Previous to this experiment,the mode of action used by cyanobacterial hemolysin had not been re-ported.To characterize the action mode of hemolysin produced by the wild-type strain of Synechocystis sp.PCC6803,hemolysis of erythrocytes originating from human,mouse,sheep,rabbit and goldfish was studied.The erythrocytes of mouse,sheep and rabbit were sensitive,while those of human and fish were resistant,to this hemolysin.Using rabbit erythrocytes,it was shown that hemoly-sis occurred in two steps:a binding step within the first 10 min of treatment and a lytic step after 30 min.Both binding and lysis were highly temperature-dependent.Effects of erythrocyte density on hemolysis suggest that the hemolysin might target erythrocytes via a multiple-hit mechanism.In the osmotic protection experiment,all tested osmotic protectants,with molecular diameters ranging from 0.9 ?5.66 nm,failed to effectively inhibit hemolysis.Scanning electron micrographs showed that the hemolysin caused protuberances or echinocytes in rabbit erythrocytes,and then disrupted and ruptured the erythrocytes.Characteristics of hemolysis showed distinct differences from other pore-forming mechanisms,suggesting that this hemolysin might act through a detergent-like or lipase mecha-nism,rather than a pore-forming mechanism.展开更多
In this study, cDNA microarrays were developed from 3569 mRNA reads to analyze the expression profiles of the transcriptomes of Synechocystis sp. PCC6803 under low temperature （LT） stress. Among the genes on the cDN...In this study, cDNA microarrays were developed from 3569 mRNA reads to analyze the expression profiles of the transcriptomes of Synechocystis sp. PCC6803 under low temperature （LT） stress. Among the genes on the cDNA microarrays, 899 LT-affected genes exhibited a 1.5-fold （or greater） difference in expression compared with the genes from normal unstressed Synechocystis sp. PCC6803. Of the differentially expressed genes, 353 were up-regulated and 246 were down-regulated. The results showed that genes involved in photosynthesis were activated at LT （10℃）, including genes for photosystem I, photosystem II, photosynthetic electron transport, and cytochrome b6/f complex. Moreover, desg, one of four genes that encode the fatty acid desaturases, was also induced by LT. However, the LT conditions to some degree enhanced the transcription of some genes. In addition, LT （10℃） may reduce cellular motility by regulating the transcription of spkA （sll1575）, a serine/threonine protein kinase. The results reported in this study may contribute to a better understanding of the responses of the Synechocystis cell to LT, including pathways involved in photosynthesis and repair.展开更多
Synthetic biology efforts have also led to the development of photosynthetic cyanobacteria as"autotrophic cell factories"for biosynthesis of various biofuels directly from CO_(2).However,the low tolerance to...Synthetic biology efforts have also led to the development of photosynthetic cyanobacteria as"autotrophic cell factories"for biosynthesis of various biofuels directly from CO_(2).However,the low tolerance to toxicity of biofuels has restricted the economic application of cyanobacterial hosts.In this study,RNAseq transcriptomics was employed to reveal stress responses to exogenous n-hexane in Synechocystis sp.PCC 6803.Functional enrichment analysis of the transcriptomic data showed that signal transduction systems were induced significantly.To further identify regulatory genes related to n-hexane tolerance,a library of transcriptional regulators(TRs)deletion mutants was then screened for their roles in nhexane tolerance.The results showed that a knockout mutant of slr0724 that encodes an Hta R suppressor protein was more tolerant to n-hexane than the wild type,indicating the involvement of slr0724 in nhexane tolerance.This study provides the foundation for better understanding the cellular responses to n-hexane in Synechocystis sp.PCC 6803,which could contribute to the further engineering of nhexane tolerance in cyanobacteria.展开更多
Photosynthetic cyanobacteria have shown great potential as“autotrophic cell factories”for the synthesis of fuels and chemicals.However,poor tolerance to various environmental stressors such as high light and heavy m...Photosynthetic cyanobacteria have shown great potential as“autotrophic cell factories”for the synthesis of fuels and chemicals.However,poor tolerance to various environmental stressors such as high light and heavy metals is an important factor limiting their economic viability.While numerous studies have focused on the tolerance mechanism of cyanobacteria to individual stressors,their response to simultaneous stresses remains to be recovered.To investigate the mechanism of cross tolerance to heavymetal Cd^(2+) and high light,the model cyanobacterium Synechocystis sp.PCC 6803 tolerant to both Cd^(2+) and high light was obtained via about 800 days’cross-adaptive laboratory evolution.Three evolutionary strains capable of tolerating both 5.5 μmol·L^(-1) Cd^(2+) and 600 μmol·m^(-2)·s^(-1) high light were successfully obtained,achieving about 83%enhancement of Cd^(2+) tolerance compared with the parent strain.The different response of parent and evolutionary strains to Cd^(2+) was elucidated via metabolomics.Furthermore,a total of 15 genes that were mutated during evolution were identified by whole-genome re-sequencing.Finally,by single-gene knockout and complementation analysis,four genes including ssl2615,sll1732,ssr1480,and sll1659 involved in the improvement of Cd^(2+) tolerance under high-light condition were successfully identified.This work explored the tolerance mechanism of Synechocystis sp.PCC 6803 to cadmium under high-light condition and provided valuable reference for deciphering multitolerance mechanism of cyanobacteria in the future.展开更多
Objective:To explore the ability of Synechocystis sp.PCC6803 in transforming 6-deoxypseudoanisatin.Methods:The experiment was performed by incubating 6-deoxypseudoanisatin with the freshwater cyanobacterium Synechocys...Objective:To explore the ability of Synechocystis sp.PCC6803 in transforming 6-deoxypseudoanisatin.Methods:The experiment was performed by incubating 6-deoxypseudoanisatin with the freshwater cyanobacterium Synechocystis sp.PCC6803 under continuous white light at 30C for 5 days.The crude converted product was detected using thin-layer chromatography(TLC)and further analyzed using high-performance liquid chromatography(HPLC)as well as HPLC with electron spray ionization mass spectrometry(HPLC-ESI-MS).Results:TLC results showed that 6-deoxypseudoanisatin was converted into a less polar product.HPLC and MS data indicated that the retention time of the converted product increased in comparison with the standard of 6-deoxypseudoanisatin.Conclusion:Thus,the study appears to demonstrate that Synechocystis sp.PCC6803 can transform 6-deoxypseudoanisatin.The polarity of the converted product is less than that of 6-deoxypseudoanisatin.展开更多
Inspired by iron fertilization experiments in HNLC（high-nitrate, low-chlorophyll） sea areas,we proposed the use of iron-rich engineered microalgae for microbial contaminant control in iron-free culture media. Based ...Inspired by iron fertilization experiments in HNLC（high-nitrate, low-chlorophyll） sea areas,we proposed the use of iron-rich engineered microalgae for microbial contaminant control in iron-free culture media. Based on the genome sequence and natural transformation system of Synechocystis sp. PCC6803, ftn A（encoding ferritin） was selected as our target gene and was cloned into wild-type Synechocystis sp. PCC6803. Tests at the molecular level confirmed the successful construction of the engineered Synechocystis sp. PCC6803-ftn A. After Fe3＋-EDTA pulsing, the intracellular iron content of Synechocystis sp. PCC6803-ftn A was significantly enhanced, and the algae was used in the microbial contamination control system. In the coupled Synechocystis sp. PCC6803-ftn A production and municipal wastewater（MW, including Scenedesmus obliquus and Bacillus） treatment, Synechocystis sp. PCC6803-ftn A accounted for all of the microbial activity and significantly increased from 70% of the microbial community to 95%.These results revealed that while the stored iron in the Synechocystis sp. PCC6803-ftn A cells was used for growth and reproduction of this microalga in the MW, the growth of other microbes was inhibited because of the iron limitation, and these results provide a new method for microbial contamination control during a coupling process.展开更多
Dear Editor,Saffron is the world’s most expensive spice,often referred to as“red gold”because of its high economic value.Crocetin and its glycosylated derivatives,crocins,are carotenoid derivatives responsible for ...Dear Editor,Saffron is the world’s most expensive spice,often referred to as“red gold”because of its high economic value.Crocetin and its glycosylated derivatives,crocins,are carotenoid derivatives responsible for the color of saffron.These compounds have at-tracted attention for their pharmaceutical and health-related ef-fects,including antioxidant,anticancer,cardioprotective,neuro-protective,antidepressant,and immune-enhancing properties(Bukhari et al.,2018).The broad potential of crocetin and crocins in food,healthcare,and cosmetics has driven increasing research into their metabolically engineered production in various microorganisms and plants(Zheng et al.,2022).展开更多
Zur(zinc uptake regulator),a member of the Fur(ferric uptake regulator)family of transcriptional regulators,plays multifaceted roles by regulating the gene expressions,such as modulating zinc ion uptake by regulating ...Zur(zinc uptake regulator),a member of the Fur(ferric uptake regulator)family of transcriptional regulators,plays multifaceted roles by regulating the gene expressions,such as modulating zinc ion uptake by regulating the znuABC gene cluster and influencing bacterial motility by modulating genes associated with flagella or pili.The photosynthetic autotroph Synechocystis sp.PCC 6803 is frequently used as an indicator organism for water pollution and a cell factory for high-value biochemical production in synthetic biology.During its growth,this organism often encounters various abiotic stresses,including oxidative,salt,and antibiotic stress.In this study,we conducted transcriptomic analysis on bothΔzur mutant and wild-type(WT)strains to identify potential Zur-regulated genes in Synechocystis sp.PCC 6803.These genes primarily participate in multiple pathways such as inorganic ion transport,carbohydrate transport,energy production and conversion,and cell motility.Zur not only controls zinc ion homeostasis within the cell but also influences the iron balance by directly regulating the expression of the fur gene.In terms of motility,Zur regulates the expression of bacterial pili gene cluster and other motility-related genes,thereby affecting the twitching motility of Synechocystis sp.PCC 6803.Furthermore,Zur plays a crucial role in promoting biofilm formation and enhancing resistance to salt,oxidative,and antibiotic stresses by modulating relative gene expression.In conclusion,as a global transcriptional regulator,Zur plays pivotal roles in metal ion homeostasis,motility,and resistance to multiple stresses in Synechocystis sp.PCC 6803.This study illustrates the Zur regulons in Synechocystis sp.PCC 6803,and underscores the importance of Zur in enhancing the environmental adaptability of cyanobacteria.Highlights 1.Transcriptome analysis of Zur’s regulons inSynechocystis sp.PCC 6803.2.Zur mediates metal homeostasis beyond zinc.3.Zur modulates pili biosynthesis and subsequent motility.4.Zur promotes biofilm formation and stresses resistance.展开更多
Glutaminase is widely distributed among microorganisms and mammals with important functions. Lit-tle is known regarding the biochemical properties and functions of the deamidating enzyme glutami-nase in cyanobacteria....Glutaminase is widely distributed among microorganisms and mammals with important functions. Lit-tle is known regarding the biochemical properties and functions of the deamidating enzyme glutami-nase in cyanobacteria. In this study a putative glutaminase encoded by gene slr2079 in Synechocystis sp. PCC 6803 was investigated. The slr2079 was expressed as histidine-tagged fusion protein in Es-cherichia coli. The purified protein possessed glutaminase activity, validating the functional assign-ment of the genomic annotation. The apparent Km value of the recombinant protein for glutamine was 26.6 ± 0.9 mmol/L, which was comparable to that for some of other microbial glutaminases. Analysis of the purified protein revealed a two-fold increase in catalytic activity in the presence of 1 mol/L Na+. Moreover, the Km value was decreased to 12.2 ± 1.9 mmol/L in the presence of Na+. These data demon-strate that the recombinant protein Slr2079 is a glutaminase which is regulated by Na+ through in-creasing its affinity for substrate glutamine. The slr2079 gene was successfully disrupted in Synecho-cystis by targeted mutagenesis and the △slr2079 mutant strain was analyzed. No differences in cell growth and oxygen evolution rate were observed between △slr2079 and the wild type under standard growth conditions, demonstrating slr2079 is not essential in Synechocystis. Under high salt stress condition, however, △slr2079 cells grew 1.25-fold faster than wild-type cells. Moreover, the photosyn-thetic oxygen evolution rate of △slr2079 cells was higher than that of the wild-type. To further charac-terize this phenotype, a number of salt stress-related genes were analyzed by semi-quantitative RT-PCR. Expression of gdhB and prc was enhanced and expression of desD and guaA was repressed in △slr2079 compared to the wild type. In addition, expression of two key enzymes of ammonium assimi-lation in cyanobacteria, glutamine synthetase (GS) and glutamate synthase (GOGAT) was examined by semi-quantitative RT-PCR. Expression of GOGAT was enhanced in △slr2079 compared to the wild type while GS expression was unchanged. The results indicate that slr2079 functions in the salt stress re-sponse by regulating the expression of salt stress related genes and might not play a major role in glutamine breakdown in Synechocystis.展开更多
基金supported by the Project of Chinese Manned Spaceflight(No.YYWT-0801-EXP-09)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA17010502)Jiangsu Province Ecological Environment Scientific Research Project(No.2022008).
文摘Perchlorate(ClO_(4)^(−))is a type of novel persistent inorganic pollutant that has gained increasing attention because of its high solubility,poor degradability,and widespread distribution.However,the impacts of perchlorate on aquatic autotrophs such cyanobacterium are still unclear.Herein,Synechocystis sp.PCC6803(Synechocystis)was used to investigate the response mechanisms of perchlorate on cyanobacterium by integrating physiological and transcriptome analyses.Physiological results showed that perchlorate mainly damaged the photosystem of Synechocystis,and the inhibition degree of photosystem II(PSII)was severer than that of photosystem I(PSI).When the exposed cells were moved to a clean medium,the photosynthetic activities were slightly repaired but still lower than in the control group,indicating irreversible damage.Furthermore,perchlorate also destroyed the cellular ultrastructure and induced oxidative stress in Synechocystis.The antioxidant glutathione(GSH)content and the superoxide dismutase(SOD)enzyme activity were enhanced to scavenge harmful reactive oxygen(ROS)in Synechocystis.Transcriptome analysis revealed that the genes associated with“photosynthesis”and“electron transport”were significantly regulated.For instance,most genes related to PSI(e.g.,psaf,psaJ)and the“electron transport chain”were upregulated,whereas most genes related to PSII(e.g.,psbA3,psbD1,psbB,and psbC)were downregulated.Additionally,perchlorate also induced the expression of genes related to the antioxidant system(sod2,gpx,gst,katG,and gshB)to reduce oxidative damage.Overall,this study is the first to investigate the impacts andmechanisms of cyanobacterium under perchlorate stress,which is conducive to assessing the risk of perchlorate in aquatic environments.
文摘The agp gene encoding the ADP-glucose pyrophosphorylase involved in cyanobacterial glycogen synthesis was amplified by PCR. The resulting agp fragment was cloned in plasmid pUC118 to generate plasmid pUCA. Part of the fragment within the agp DNA was deleted and replaced by an erythromycin resistance cassette to generate plasmid pUCAE, which was used to transform the Synechocystis sp. PCC 6803 wild-type strain and a mutant with resistance to erythromycin was obtained. PCR analysis of the genomic DNA from the resulting mutant indicated that the appropriate deletion and insertion indeed had occurred. The cell growth and Chl a, glycogen content in the mutant showed difference from those in the wild-type strain. The obtained biomass as well as the Chl a content in the mutant strain was higher than that of the wild-type strain, which suggested that the photosynthesis efficiency in the agp(-) strain was higher than that in the wild-type strain. No glycogen was found in the mutant, providing evidence for the correction of the mutant in physiological level.
文摘Compositions of glycerolipids and fatty acid compositions of glycerolipids were compared among Synechocystis sp. PCC 6803 cells grown in the BG-11 medium containing different concentrations of glucose and Na2S2O3 in this study. It was found that Na2S2O3 can effectively increase the percentage of sulphoquinovosyl diacylglycerol (SQDG) and phosphatidylglycerol (PG) to total membrane lipids and the simultaneous application of glucose with Na2S2O3 can counteract the effect of Na2S2O3. In addition, Na2S2O3 can significantly increase the percentage of palmitic acid (C, 16:0) in fatty acid composition of monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) and decrease the fatty acid unsaturation degree accordingly, and these effects can also be eliminated by glucose. These results indicate that Na2S2O3 can take as a reductant to make membrane lipids in a low unsaturated state, and the simultaneous application of glucose can decrease the reducing power of Na2S2O3. In addition, Na2S2O3 can take as a sulfur donor for the synthesis of SQDG.
基金Supported by the National Natural Science Foundation of China(Nos.40972043,41040018,41210104058,21176145,41372108,41302079)the Higher Educational Science and Technology Program of Shandong Province(No.J10LC15)+4 种基金the China Postdoctoral Science Foundation(No.2013M540560)the Program for Scientific Research Innovation Team in Colleges and Universities of Shandong Province,and SDUST Research Fund(No.2010KYTD103)the Open Project of Key Lab of Marine Bioactive Substance and Modern Analytical Technique,State Oceanic Administration,China(No.MBSMAT-2012-03)the Scientific and Technological Program of Qingdao(No.13-1-4-232-jch)the Domestic Visiting Scholar Program for Young Core Teachers in Shandong Universities,Shandong Province,China
文摘Calcium carbonate （CaCO3） crystals in their preferred orientation were obtained in BG11 culture media inoculated with Synechocystis sp. PCC6803 （inoculated BG11）. In this study, the features of calcium carbonate deposition were investigated. Inoculated BGll in different calcium ion concentrations was used for the experimental group, while the BGll culture medium was used for the control group. The surface morphologies of the calcium carbonate deposits in the experimental and control groups were determined by scanning and transmission electron microscopy. The deposits were analyzed by electronic probe micro-analysis, Fourier transform infrared spectrum, X-ray diffraction, thermal gravimetric analysis and differential scanning calorimetry. The results show that the surfaces of the crystals in the experimental group were hexahedral in a scaly pattern. The particle sizes were micrometer-sized and larger than those in the control group. The deposits of the control group contained calcium （Ca）, carbon （C）, oxygen （O）, phosphorus （P）, iron （Fe）, copper （Cu）, zinc （Zn）, and other elements. The deposits in the experimental group contained Ca, C, and O only. The deposits of both groups contained calcite. The thermal decomposition temperature of the deposits in the control group was lower than those in the experimental group. It showed that the CaCO3 deposits of the experimental group had higher thermal stability than those of the control group. This may be due to the secondary metabolites produced by the algae cells, which affect the carbonate crystal structure and result in a close-packed structure. The algae cells that remained after thermal weight loss were heavier in higher calcium concentrations in BGll culture media. There may be more calcium- containing crystals inside and outside of these cells. These results shall be beneficial for understanding the formation mechanism of carbonate minerals.
基金supported by the National Key Scienceand Technology Program of China (No. 2008ZX07105-006)the National Natural Science Foundation of China(No. 30821140542) the Hundred Talents Program of the Chinese Academy of Sciences (No. 0823031501)
文摘In order to explore the mechanism of acute toxicity for pyrene to cyanobacterial organisms, the responses of Synechocystis sp. PCC 6803 photosystem Ⅱ （PS Ⅱ） under pyrene stress were studied. The results showed there was no significant difference about the oxygen evolution under 0.125 mg/L pyrene stress when compared with control, but it was significantly lower than control at 0.625 mg/L pyrene. Polyphasic chlorophyll-a fluorescence transients in cells of Synechocystis sp. PCC 6803 exhibited a typical increase including O, J, I, and P phases. Fluorescence yield at phases J, I and P declined slightly at 0.125 and 0.625 mg/L pyrene, and significantly lower than control at 3.125 mg/L. According to the parameters deviated from JIP-test, no modification was induced by pyrene both at the donor side and at the acceptor side of PS Ⅱ, and the reaction centre of PS Ⅱ is the primary damaging target. Based on the expressing of four key genes （psbA, psbB, psbC and psbO） of PS Ⅱ, only psbA showed significant difference at 3.125 mg/L pyrene when compared with control.
文摘The unicellular cyanobacterium Synechocystis sp. PCC 6803, a model organism known for its unique combination of highly desirable molecular genetic, physiological and morphological characteristics, was employed in the present study. The species was cultured in BG11 liquid medium contained various initial concentrations of Pb^2＋ and Cd〉 （0, 0.5, 1, 2, 4, 6 and 8 mg/L）. The experiment was conducted for six days and the metal induced alterations in the ultrastructure, growth and pigment contents were assessed. Alterations in the ultrastructure of the Synechocystis sp. PCC 6803 cells became evident with the increased （〉4 mg/L Pb^2＋） metal concentration. The photosynthetic apparatus （thylakoid membranes） were found to be the worst affected. Deteriorated or completely destroyed thylakoid membranes have made large empty spaces in the cell interior. In addition, at the highest concentration （8 mg/L pb^2＋）, the polyphosphate granules became more prominent both in size and number. Despite the initial slight stimulations （0.2, 3.8 and 6.5% respectively at 0.5, 1 and 2 mg/L pb^2＋）, both metals inhibited the growth in a dose-dependent manner as incubation progressed. Pigment contents （chlorophyll a, 13 carotene and phycocyanin） were also decreased with increasing metal concentration. Cells exposed to 6 mg/L Pb^2＋, resulted in 36.56, 37.39 and 29.34% reductions of chlorophyll a, 13 carotene and phycocyanin respectively over the control. Corresponding reductions for the same CdZ＋concentrations were 57.83, 48.94 and 56.90%. Lethal concentration （96 h LC50） values （3.47 mg/L Cd^2＋ and 12.11 mg/L Pb^2＋） indicated that Synechocystis sp. PCC 6803 is more vulnerable to Cd^2＋ than Pb^2＋.
基金Supported by the National Key Research and Development Program of China(No.2016YFF0202304)the National Natural Science Foundation of China(No.41376139)+1 种基金the Science and Technology Program of Yantai City(No.2016JHZB007)Natural Science Foundation of Shandong Province,China(No.ZR2016CM48)
文摘Synechocystis sp. PCC 6803 is a model organism widely used in cyanobacterium biology and biotechnology. To know the genetic background of substrains of Synechocystis sp. PCC 6803 is important for further research and application. In this study, we reported the genome sequences of two non-motile wild-type substrains of Synechocystis sp. PCC 6803 using whole genome resequencing. 55/56 putative single nucleotide polymorphisms(SNPs) and 8/9 Indels(insertion and deletion) were identified. Among these, 47 SNPs were found in both the GT-AR and GT-CH strains, and 8 were unique to GT-AR and 9 were unique to GT-CH. All of these variations were annotated in metabolism pathway referred to KEGG database. Meanwhile, the deletion in s lr0332 gene was detected in these two strains, which attributed to the non-motile phenotype of them and suggested that the insertion in spkA gene was not essential for non-motile phenotype. These resequencing data provide the genetic background information of these two strains and highlighted the microevolution over decades of laboratory cultivation.
基金the National Natural Science Fund of China (No. 30870250)Shandong Provincial NaturalScience Fund (No. Q2006D09)
文摘Hemolysin produced by various bacteria,may destroy erythrocyte membranes via a pore-forming mechanism,a deter-gent action,or a lipase activity.Previous to this experiment,the mode of action used by cyanobacterial hemolysin had not been re-ported.To characterize the action mode of hemolysin produced by the wild-type strain of Synechocystis sp.PCC6803,hemolysis of erythrocytes originating from human,mouse,sheep,rabbit and goldfish was studied.The erythrocytes of mouse,sheep and rabbit were sensitive,while those of human and fish were resistant,to this hemolysin.Using rabbit erythrocytes,it was shown that hemoly-sis occurred in two steps:a binding step within the first 10 min of treatment and a lytic step after 30 min.Both binding and lysis were highly temperature-dependent.Effects of erythrocyte density on hemolysis suggest that the hemolysin might target erythrocytes via a multiple-hit mechanism.In the osmotic protection experiment,all tested osmotic protectants,with molecular diameters ranging from 0.9 ?5.66 nm,failed to effectively inhibit hemolysis.Scanning electron micrographs showed that the hemolysin caused protuberances or echinocytes in rabbit erythrocytes,and then disrupted and ruptured the erythrocytes.Characteristics of hemolysis showed distinct differences from other pore-forming mechanisms,suggesting that this hemolysin might act through a detergent-like or lipase mecha-nism,rather than a pore-forming mechanism.
基金Supported by the National Natural Science Foundation of China(No.40876082)the International Innovation Partnership Program:Typical Environmental Process and Effects on Resources in Coastal Zone Area+3 种基金the Public Science and Technology Research Funds Projects of the Ocean(Nos.200905021,201205027)the Outstanding Young Scholars Fellowship of Shandong Province(Molecular Phycology,No.JQ200914)the Natural Science Foundation of Shandong Province(No.ZR2012DQ015)the Guangdong Province Comprehensive Strategic Cooperation Project of the Chinese Academy of Sciences(No.2011A090100040)
文摘In this study, cDNA microarrays were developed from 3569 mRNA reads to analyze the expression profiles of the transcriptomes of Synechocystis sp. PCC6803 under low temperature （LT） stress. Among the genes on the cDNA microarrays, 899 LT-affected genes exhibited a 1.5-fold （or greater） difference in expression compared with the genes from normal unstressed Synechocystis sp. PCC6803. Of the differentially expressed genes, 353 were up-regulated and 246 were down-regulated. The results showed that genes involved in photosynthesis were activated at LT （10℃）, including genes for photosystem I, photosystem II, photosynthetic electron transport, and cytochrome b6/f complex. Moreover, desg, one of four genes that encode the fatty acid desaturases, was also induced by LT. However, the LT conditions to some degree enhanced the transcription of some genes. In addition, LT （10℃） may reduce cellular motility by regulating the transcription of spkA （sll1575）, a serine/threonine protein kinase. The results reported in this study may contribute to a better understanding of the responses of the Synechocystis cell to LT, including pathways involved in photosynthesis and repair.
基金supported by grants from the National Key Research and Development Program of China(2020YFA0906800,2021YFA0909700,2018YFA0903600 and 2019YFA0904600)。
文摘Synthetic biology efforts have also led to the development of photosynthetic cyanobacteria as"autotrophic cell factories"for biosynthesis of various biofuels directly from CO_(2).However,the low tolerance to toxicity of biofuels has restricted the economic application of cyanobacterial hosts.In this study,RNAseq transcriptomics was employed to reveal stress responses to exogenous n-hexane in Synechocystis sp.PCC 6803.Functional enrichment analysis of the transcriptomic data showed that signal transduction systems were induced significantly.To further identify regulatory genes related to n-hexane tolerance,a library of transcriptional regulators(TRs)deletion mutants was then screened for their roles in nhexane tolerance.The results showed that a knockout mutant of slr0724 that encodes an Hta R suppressor protein was more tolerant to n-hexane than the wild type,indicating the involvement of slr0724 in nhexane tolerance.This study provides the foundation for better understanding the cellular responses to n-hexane in Synechocystis sp.PCC 6803,which could contribute to the further engineering of nhexane tolerance in cyanobacteria.
基金supported by grants from the National Key Research and Development Programof China(2018YFA0903600)well as the National Natural Science Foundation of China(32371486 and 32270091).
文摘Photosynthetic cyanobacteria have shown great potential as“autotrophic cell factories”for the synthesis of fuels and chemicals.However,poor tolerance to various environmental stressors such as high light and heavy metals is an important factor limiting their economic viability.While numerous studies have focused on the tolerance mechanism of cyanobacteria to individual stressors,their response to simultaneous stresses remains to be recovered.To investigate the mechanism of cross tolerance to heavymetal Cd^(2+) and high light,the model cyanobacterium Synechocystis sp.PCC 6803 tolerant to both Cd^(2+) and high light was obtained via about 800 days’cross-adaptive laboratory evolution.Three evolutionary strains capable of tolerating both 5.5 μmol·L^(-1) Cd^(2+) and 600 μmol·m^(-2)·s^(-1) high light were successfully obtained,achieving about 83%enhancement of Cd^(2+) tolerance compared with the parent strain.The different response of parent and evolutionary strains to Cd^(2+) was elucidated via metabolomics.Furthermore,a total of 15 genes that were mutated during evolution were identified by whole-genome re-sequencing.Finally,by single-gene knockout and complementation analysis,four genes including ssl2615,sll1732,ssr1480,and sll1659 involved in the improvement of Cd^(2+) tolerance under high-light condition were successfully identified.This work explored the tolerance mechanism of Synechocystis sp.PCC 6803 to cadmium under high-light condition and provided valuable reference for deciphering multitolerance mechanism of cyanobacteria in the future.
基金Beijing University of Chinese Medicine(2013-JYBZZ-JS-139)Independent Project Topics Foundation.
文摘Objective:To explore the ability of Synechocystis sp.PCC6803 in transforming 6-deoxypseudoanisatin.Methods:The experiment was performed by incubating 6-deoxypseudoanisatin with the freshwater cyanobacterium Synechocystis sp.PCC6803 under continuous white light at 30C for 5 days.The crude converted product was detected using thin-layer chromatography(TLC)and further analyzed using high-performance liquid chromatography(HPLC)as well as HPLC with electron spray ionization mass spectrometry(HPLC-ESI-MS).Results:TLC results showed that 6-deoxypseudoanisatin was converted into a less polar product.HPLC and MS data indicated that the retention time of the converted product increased in comparison with the standard of 6-deoxypseudoanisatin.Conclusion:Thus,the study appears to demonstrate that Synechocystis sp.PCC6803 can transform 6-deoxypseudoanisatin.The polarity of the converted product is less than that of 6-deoxypseudoanisatin.
基金supported by the National Key Technologies R&D Program of China(No.2012BAJ25B02)
文摘Inspired by iron fertilization experiments in HNLC（high-nitrate, low-chlorophyll） sea areas,we proposed the use of iron-rich engineered microalgae for microbial contaminant control in iron-free culture media. Based on the genome sequence and natural transformation system of Synechocystis sp. PCC6803, ftn A（encoding ferritin） was selected as our target gene and was cloned into wild-type Synechocystis sp. PCC6803. Tests at the molecular level confirmed the successful construction of the engineered Synechocystis sp. PCC6803-ftn A. After Fe3＋-EDTA pulsing, the intracellular iron content of Synechocystis sp. PCC6803-ftn A was significantly enhanced, and the algae was used in the microbial contamination control system. In the coupled Synechocystis sp. PCC6803-ftn A production and municipal wastewater（MW, including Scenedesmus obliquus and Bacillus） treatment, Synechocystis sp. PCC6803-ftn A accounted for all of the microbial activity and significantly increased from 70% of the microbial community to 95%.These results revealed that while the stored iron in the Synechocystis sp. PCC6803-ftn A cells was used for growth and reproduction of this microalga in the MW, the growth of other microbes was inhibited because of the iron limitation, and these results provide a new method for microbial contamination control during a coupling process.
基金supported by baseline funding and the Opportunity Fund Program(OFP,2023)awarded to S.A.-B.by King Abdullah University of Science and Technology(KAUST).
文摘Dear Editor,Saffron is the world’s most expensive spice,often referred to as“red gold”because of its high economic value.Crocetin and its glycosylated derivatives,crocins,are carotenoid derivatives responsible for the color of saffron.These compounds have at-tracted attention for their pharmaceutical and health-related ef-fects,including antioxidant,anticancer,cardioprotective,neuro-protective,antidepressant,and immune-enhancing properties(Bukhari et al.,2018).The broad potential of crocetin and crocins in food,healthcare,and cosmetics has driven increasing research into their metabolically engineered production in various microorganisms and plants(Zheng et al.,2022).
基金supported by grants of the National Key R&D Program of China(Grants 2021YFA0909600 to X.S.and Y.Y.)National Natural Science Foundation of China(32370048 to Y.Y.,Grants 31725003 and 32330004 to X.S.).
文摘Zur(zinc uptake regulator),a member of the Fur(ferric uptake regulator)family of transcriptional regulators,plays multifaceted roles by regulating the gene expressions,such as modulating zinc ion uptake by regulating the znuABC gene cluster and influencing bacterial motility by modulating genes associated with flagella or pili.The photosynthetic autotroph Synechocystis sp.PCC 6803 is frequently used as an indicator organism for water pollution and a cell factory for high-value biochemical production in synthetic biology.During its growth,this organism often encounters various abiotic stresses,including oxidative,salt,and antibiotic stress.In this study,we conducted transcriptomic analysis on bothΔzur mutant and wild-type(WT)strains to identify potential Zur-regulated genes in Synechocystis sp.PCC 6803.These genes primarily participate in multiple pathways such as inorganic ion transport,carbohydrate transport,energy production and conversion,and cell motility.Zur not only controls zinc ion homeostasis within the cell but also influences the iron balance by directly regulating the expression of the fur gene.In terms of motility,Zur regulates the expression of bacterial pili gene cluster and other motility-related genes,thereby affecting the twitching motility of Synechocystis sp.PCC 6803.Furthermore,Zur plays a crucial role in promoting biofilm formation and enhancing resistance to salt,oxidative,and antibiotic stresses by modulating relative gene expression.In conclusion,as a global transcriptional regulator,Zur plays pivotal roles in metal ion homeostasis,motility,and resistance to multiple stresses in Synechocystis sp.PCC 6803.This study illustrates the Zur regulons in Synechocystis sp.PCC 6803,and underscores the importance of Zur in enhancing the environmental adaptability of cyanobacteria.Highlights 1.Transcriptome analysis of Zur’s regulons inSynechocystis sp.PCC 6803.2.Zur mediates metal homeostasis beyond zinc.3.Zur modulates pili biosynthesis and subsequent motility.4.Zur promotes biofilm formation and stresses resistance.
基金Supported by the National Natural Sciences Foundation of China (Grant No. 30500108)Hundred Talents Program of Chinese Academy of Sciences
文摘Glutaminase is widely distributed among microorganisms and mammals with important functions. Lit-tle is known regarding the biochemical properties and functions of the deamidating enzyme glutami-nase in cyanobacteria. In this study a putative glutaminase encoded by gene slr2079 in Synechocystis sp. PCC 6803 was investigated. The slr2079 was expressed as histidine-tagged fusion protein in Es-cherichia coli. The purified protein possessed glutaminase activity, validating the functional assign-ment of the genomic annotation. The apparent Km value of the recombinant protein for glutamine was 26.6 ± 0.9 mmol/L, which was comparable to that for some of other microbial glutaminases. Analysis of the purified protein revealed a two-fold increase in catalytic activity in the presence of 1 mol/L Na+. Moreover, the Km value was decreased to 12.2 ± 1.9 mmol/L in the presence of Na+. These data demon-strate that the recombinant protein Slr2079 is a glutaminase which is regulated by Na+ through in-creasing its affinity for substrate glutamine. The slr2079 gene was successfully disrupted in Synecho-cystis by targeted mutagenesis and the △slr2079 mutant strain was analyzed. No differences in cell growth and oxygen evolution rate were observed between △slr2079 and the wild type under standard growth conditions, demonstrating slr2079 is not essential in Synechocystis. Under high salt stress condition, however, △slr2079 cells grew 1.25-fold faster than wild-type cells. Moreover, the photosyn-thetic oxygen evolution rate of △slr2079 cells was higher than that of the wild-type. To further charac-terize this phenotype, a number of salt stress-related genes were analyzed by semi-quantitative RT-PCR. Expression of gdhB and prc was enhanced and expression of desD and guaA was repressed in △slr2079 compared to the wild type. In addition, expression of two key enzymes of ammonium assimi-lation in cyanobacteria, glutamine synthetase (GS) and glutamate synthase (GOGAT) was examined by semi-quantitative RT-PCR. Expression of GOGAT was enhanced in △slr2079 compared to the wild type while GS expression was unchanged. The results indicate that slr2079 functions in the salt stress re-sponse by regulating the expression of salt stress related genes and might not play a major role in glutamine breakdown in Synechocystis.
