The effect of iron deficiency on heterocyst differentiation and some physiological properties of the filamentous cyanobacterium Anabaena sp. PCC 7120 was investigated. Under moderate iron limitation conditions, ac...The effect of iron deficiency on heterocyst differentiation and some physiological properties of the filamentous cyanobacterium Anabaena sp. PCC 7120 was investigated. Under moderate iron limitation conditions, achieved by addition of iron chelator 2,2′\|Dipyridyl (<80 μmol/L) led to delayed heterocyst differentiation, no heterocyst differentiation was observed under severe iron limitation conditions, when the concentration of 2,2′\|Dipyridyl in the medium was more than 100 μmol/L . It seemed that there are certain iron\|regulated genes or operons whose function is to control heterocyst development. In addition, iron deficiency impaired the growth. Low\|iron cells had a decrease in the quantities of pigment content (chlorophyll and phycocyanin content),the whole cell in vivo absorbance spectra confirmed the decrease, the protein electrophoretic profiles revealed that iron\|deficient cells had less protein bands, with the increase of 2,2′\|Dipyridyl ,the protein bands was more and more less. And differently, iron deficiency also caused an increase of ROS (Reactive Oxygen Species)and SOD activity, it suggests that iron deficiency led to oxidative stress, which generally occured under high\|iron conditions.展开更多
Upon nitrogen step-down, Anabaena sp. PCC 7120 produces semi-regularly spaced heterocysts along filaments. HetR, the master regulator of heterocyst differenti- ation, has been shown to up-regulate hetP and hetZ in dif...Upon nitrogen step-down, Anabaena sp. PCC 7120 produces semi-regularly spaced heterocysts along filaments. HetR, the master regulator of heterocyst differenti- ation, has been shown to up-regulate hetP and hetZ in differentiating heterocysts via specific recognition sites. HetR is also predicted to bind to the promoter of patA, a gene required for heterocyst formation at intercalary positions. Here, we show that HetR binds to the predicted site 5′ from patA. Moreover, （1） deletion of the HetR-binding site greatly diminished the expression ofpatA in vegetative cells as shown with gfp, and （2） complementation of a patA mutant by a replicating plasmid that bears patA is largely prevented by removal of that binding site. In contrast, HetR- binding sites suppressed the expression of alr0202 （a homolog of hetZ） specifically in heterocysts and of alr3234 （a homolog of hetP） in whole filaments. Our results indicate that HetR can regulate gene expression in different modes.展开更多
Some filamentous cyanobacteria form heterocysts under conditions lacking combined nitrogen for nitrogen fixation.Photosystem II is removed from heterocyst during the process of cell differentiation.Here,we demonstrate...Some filamentous cyanobacteria form heterocysts under conditions lacking combined nitrogen for nitrogen fixation.Photosystem II is removed from heterocyst during the process of cell differentiation.Here,we demonstrate that Alr3815 is a protease that is capable of degrading D1 protein of photosystem II.Strain-322,which lacks alr3815,is impaired in nitrogen fixation in air because some oxygen evolving activity is retained in its heterocysts.Our results also suggest that calcium may play a regulatory role in D1 degradation during heterocyst differentiation.展开更多
Microcystis aeruginosa has always been regarded as the main culprit of cyanobacterial blooms in freshwater.However,in recent years,Raphidiopsis raciborskii has gradually replaced M.aeruginosa as the culprit of cyanoba...Microcystis aeruginosa has always been regarded as the main culprit of cyanobacterial blooms in freshwater.However,in recent years,Raphidiopsis raciborskii has gradually replaced M.aeruginosa as the culprit of cyanobacterial blooms in some tropical and subtropical shallow lakes.To reveal which one plays a more dominant role,interactions between cylindrospermospin(CYN)-producing R.raciborskii and microcystins(MCs)-producing or non-MCs-producing M.aeruginosa strains were studied using bialgal cultures at different initial ratios of biomasses of the two species at 25℃.During the co-cultivation,the M.aeruginosa strains inhibited the growth and heterocyst formation of R.raciborskii filaments,and thus occupied a dominant position during the co-cultivation regardless of the initial biomass ratios in the cultures.In addition,the MCs-producing M aeruginosa strain contributed to a higher portion of the total biomass and exerted a stronger inhibitory effect on R.raciborskii compared with the non-MCs-producing strain.However,the growth of both MCs-producing and non-MCs-producing M.aeruginosa strains was stimulated by R.raciborskii in the co-cultures compared with M.aeruginosa monoculture,indicating that M.aeruginosa could outcompete R.raciborskii if given enough time,enabling it to develop into the dominant species even in very low initial concentration.To our best knowledge,this is the first report on the loss of heterocyst formation by a species of cyanobacteria that resulted from interactions between two different species of cyanobacteria.These findings indicate that it is difficult for R.raciborskii to replace the dominant position of M.aeruginosa under the experimental environmental condition,and the allelopathic effects of M.aeruginosa on R.raciborskii could significantly contribute to the success of M.aeruginosa.展开更多
In this study we show that cylindrospermopsin (a cyanotoxin) content of filaments of Aphanizomenon ovalisporum ILC164 depended on growth on combined nitrogen or nitrogen fixation. Our results also demonstrated that th...In this study we show that cylindrospermopsin (a cyanotoxin) content of filaments of Aphanizomenon ovalisporum ILC164 depended on growth on combined nitrogen or nitrogen fixation. Our results also demonstrated that the shift down of cyanobacterial filaments from combined nitrogen to dinitrogen fixing condition resulted in a significant decrease of cylindrospermopsin pool size which resumed a growth rate dependent manner as the heterocyst and nitrogenase formation appeared. The current study indicated that alteration of nitrogen metabolism of Aphanizomenon ovalisporum (Forti) induced changes in cyanotoxin (cylindrospermopsin) metabolism. In addition, this is the first report that isolated heterocysts, the differentiated anaerobic cells for nitrogen fixation of cyanobacteria, did not contain cylindrospermopsin.展开更多
文摘The effect of iron deficiency on heterocyst differentiation and some physiological properties of the filamentous cyanobacterium Anabaena sp. PCC 7120 was investigated. Under moderate iron limitation conditions, achieved by addition of iron chelator 2,2′\|Dipyridyl (<80 μmol/L) led to delayed heterocyst differentiation, no heterocyst differentiation was observed under severe iron limitation conditions, when the concentration of 2,2′\|Dipyridyl in the medium was more than 100 μmol/L . It seemed that there are certain iron\|regulated genes or operons whose function is to control heterocyst development. In addition, iron deficiency impaired the growth. Low\|iron cells had a decrease in the quantities of pigment content (chlorophyll and phycocyanin content),the whole cell in vivo absorbance spectra confirmed the decrease, the protein electrophoretic profiles revealed that iron\|deficient cells had less protein bands, with the increase of 2,2′\|Dipyridyl ,the protein bands was more and more less. And differently, iron deficiency also caused an increase of ROS (Reactive Oxygen Species)and SOD activity, it suggests that iron deficiency led to oxidative stress, which generally occured under high\|iron conditions.
基金supported by the National Natural Science Foundation of China(31270132)
文摘Upon nitrogen step-down, Anabaena sp. PCC 7120 produces semi-regularly spaced heterocysts along filaments. HetR, the master regulator of heterocyst differenti- ation, has been shown to up-regulate hetP and hetZ in differentiating heterocysts via specific recognition sites. HetR is also predicted to bind to the promoter of patA, a gene required for heterocyst formation at intercalary positions. Here, we show that HetR binds to the predicted site 5′ from patA. Moreover, （1） deletion of the HetR-binding site greatly diminished the expression ofpatA in vegetative cells as shown with gfp, and （2） complementation of a patA mutant by a replicating plasmid that bears patA is largely prevented by removal of that binding site. In contrast, HetR- binding sites suppressed the expression of alr0202 （a homolog of hetZ） specifically in heterocysts and of alr3234 （a homolog of hetP） in whole filaments. Our results indicate that HetR can regulate gene expression in different modes.
基金supported by the National Natural Sciences Foundation of China(30230040)
文摘Some filamentous cyanobacteria form heterocysts under conditions lacking combined nitrogen for nitrogen fixation.Photosystem II is removed from heterocyst during the process of cell differentiation.Here,we demonstrate that Alr3815 is a protease that is capable of degrading D1 protein of photosystem II.Strain-322,which lacks alr3815,is impaired in nitrogen fixation in air because some oxygen evolving activity is retained in its heterocysts.Our results also suggest that calcium may play a regulatory role in D1 degradation during heterocyst differentiation.
基金Supported by the National Key R&D Program of China(No.2018YFE0103700)the National Natural Science Foundation of China(Nos.41876124,61871293,42007372)the Zhejiang Provincial Natural Science Foundation of China(Nos.LZ21C030001,LQ20C030008,LD21C030001,LQ18C030002)。
文摘Microcystis aeruginosa has always been regarded as the main culprit of cyanobacterial blooms in freshwater.However,in recent years,Raphidiopsis raciborskii has gradually replaced M.aeruginosa as the culprit of cyanobacterial blooms in some tropical and subtropical shallow lakes.To reveal which one plays a more dominant role,interactions between cylindrospermospin(CYN)-producing R.raciborskii and microcystins(MCs)-producing or non-MCs-producing M.aeruginosa strains were studied using bialgal cultures at different initial ratios of biomasses of the two species at 25℃.During the co-cultivation,the M.aeruginosa strains inhibited the growth and heterocyst formation of R.raciborskii filaments,and thus occupied a dominant position during the co-cultivation regardless of the initial biomass ratios in the cultures.In addition,the MCs-producing M aeruginosa strain contributed to a higher portion of the total biomass and exerted a stronger inhibitory effect on R.raciborskii compared with the non-MCs-producing strain.However,the growth of both MCs-producing and non-MCs-producing M.aeruginosa strains was stimulated by R.raciborskii in the co-cultures compared with M.aeruginosa monoculture,indicating that M.aeruginosa could outcompete R.raciborskii if given enough time,enabling it to develop into the dominant species even in very low initial concentration.To our best knowledge,this is the first report on the loss of heterocyst formation by a species of cyanobacteria that resulted from interactions between two different species of cyanobacteria.These findings indicate that it is difficult for R.raciborskii to replace the dominant position of M.aeruginosa under the experimental environmental condition,and the allelopathic effects of M.aeruginosa on R.raciborskii could significantly contribute to the success of M.aeruginosa.
文摘In this study we show that cylindrospermopsin (a cyanotoxin) content of filaments of Aphanizomenon ovalisporum ILC164 depended on growth on combined nitrogen or nitrogen fixation. Our results also demonstrated that the shift down of cyanobacterial filaments from combined nitrogen to dinitrogen fixing condition resulted in a significant decrease of cylindrospermopsin pool size which resumed a growth rate dependent manner as the heterocyst and nitrogenase formation appeared. The current study indicated that alteration of nitrogen metabolism of Aphanizomenon ovalisporum (Forti) induced changes in cyanotoxin (cylindrospermopsin) metabolism. In addition, this is the first report that isolated heterocysts, the differentiated anaerobic cells for nitrogen fixation of cyanobacteria, did not contain cylindrospermopsin.
