This study aimed to increase bacterial growth and 5-aminolevulinic acid（ALA） biosynthesis of Rhodobacter sphaeroides in wastewater treatment through adding ferrous ion（ Fe2＋ ）. Results demonstrated that Fe2＋ eff...This study aimed to increase bacterial growth and 5-aminolevulinic acid（ALA） biosynthesis of Rhodobacter sphaeroides in wastewater treatment through adding ferrous ion（ Fe2＋ ）. Results demonstrated that Fe2＋ effectively enhanced the biomass production and ALA yield of R. sphaeroides. Moreover, the optimal Fe2＋ dosage was found to be 400 μmol/L, which was associated with the highest biomass of 4015.3 mg/L and maximum ALA yield of 15.9 mg/g-dry cell weight（mg/g-DCW）. Mechanism analysis revealed that Fe2＋ vastly improved Adenosine Triphosphate（ATP） production by up-regulating the nif gene expression, and increasing ATP enhanced the biomass and ALA yield by supplying energy for bacterial growth and ALA biosynthesis, respectively. Correlation analysis showed that the ALA and ATP yields had positive relation with nifA and nifU gene expression. In addition, the nifA and nifU gene expression displayed high consistency of co-transcription at the optimal Fe2＋ dosage.展开更多
[Objective]The nitrogen fixation(nif)gene operon(nifBHDKEfNXhesAniJV)ofPaenibacillus polymyxa WLY78 encoding the nitrogenase enabled Escherichia coli to synthesize functional nitrogenase.The genome-wide transcriptiona...[Objective]The nitrogen fixation(nif)gene operon(nifBHDKEfNXhesAniJV)ofPaenibacillus polymyxa WLY78 encoding the nitrogenase enabled Escherichia coli to synthesize functional nitrogenase.The genome-wide transcriptional profiling of the recombinant E.coli 78-7 was examined for improving its nitrogenase activity.[Methods]The transcriptomic analysis of the recombinant E.coli 78-7 cultured under non-N_(2)-fixing(air and 100 mmol/L NH_(4)^(+))and N_(2)-fixing(without O_(2)and NH_(4)^(+))conditions was implemented.[Results]These results reveal that n/f genes were significantly transcribed under both conditions,indicating that the negative regulation of nifgene transcription by O_(2)and NH_(4)^(+)is bypassed in heterogeneous E.coli.The non-n/f genes specifically required for nitrogen fixation,such as mod,cys and feoAB encoding transporters of Mo,S,Fe and electron transporters,respectively,were transcribed at different levels in both conditions.The transcription levels of sufoperon and isc system specific for the synthesis of the Fe-S cluster varied greatly.The genes involved in nitrogen metabolism were notably up-regulated in N_(2)-fixing conditions.[Conclusion]These data suggest that the non-n/f genes specifically required for nitrogen fixation in recombinant E.coli had obvious effects on its expression of nitrogenase.Our results will provide valuable exploration regarding the improvement for nitrogenase activity of heterogeneous hosts.展开更多
Legumes play critical roles in agroecosystems by modulating nitrogen-fixing microorganisms to enhance soil fertility and promote crop productivity.Current research on the effects of legumes predominantly focuses on su...Legumes play critical roles in agroecosystems by modulating nitrogen-fixing microorganisms to enhance soil fertility and promote crop productivity.Current research on the effects of legumes predominantly focuses on surface soil,lacking a comprehensive analysis of their overall impact across multiple soil layers and an in-depth understanding of associated microbial mechanisms.Here,the community structure of soil nitrogen-fixing microorganisms in three soil layers(0-20 cm,20-50 cm and 50-100 cm)under legume and non-legume cultivation was investigated through metagenomic sequencing.We found that only in topsoil(0-20 cm)legume treatment exhibited a significantly higher relative abundance of nitrogen-fixing genes than non-legume treatment.Under legume cultivation,the relative abundance of nitrogen-fixing genes was significantly higher in the topsoil layer than in deeper layers,whereas non-legume treatment displayed an inverse depth-dependent pattern.Combining soil physicochemical properties,the relative abundance of nitrogen-fixing genes correlated significantly with soil moisture,total carbon(TC),and dissolved organic carbon(DOC)content.Both TC and DOC were identified as key drivers of these genes.Subsequently,a similar depth-dependent pattern within the relative abundance of soil carbon degradation genes was found in response to the cultivation of both crops.The relative abundances of soil carbon degradation genes were negatively correlated with nitrogen-fixing genes under legume treatment individually,distinct from non-legume treatment.Our findings highlight the depth-dependent impact of legumes on nitrogen fixation and the critical interaction between soil carbon degradation and nitrogen fixation,providing insights into carbon management in legume cultivation practices to enhance nitrogen fixation in future agriculture.展开更多
基金supported by the National Natural Science Foundation of China(No.51708214)the High-level Personnel Research Startup Project of North China University of Water Resources and Electric Power(No.40550)the Treatment Technology Integration and Demonstration for Domestic Sewage of Typical Villages and Towns in Henan Province(No.161100310700)
文摘This study aimed to increase bacterial growth and 5-aminolevulinic acid（ALA） biosynthesis of Rhodobacter sphaeroides in wastewater treatment through adding ferrous ion（ Fe2＋ ）. Results demonstrated that Fe2＋ effectively enhanced the biomass production and ALA yield of R. sphaeroides. Moreover, the optimal Fe2＋ dosage was found to be 400 μmol/L, which was associated with the highest biomass of 4015.3 mg/L and maximum ALA yield of 15.9 mg/g-dry cell weight（mg/g-DCW）. Mechanism analysis revealed that Fe2＋ vastly improved Adenosine Triphosphate（ATP） production by up-regulating the nif gene expression, and increasing ATP enhanced the biomass and ALA yield by supplying energy for bacterial growth and ALA biosynthesis, respectively. Correlation analysis showed that the ALA and ATP yields had positive relation with nifA and nifU gene expression. In addition, the nifA and nifU gene expression displayed high consistency of co-transcription at the optimal Fe2＋ dosage.
文摘[Objective]The nitrogen fixation(nif)gene operon(nifBHDKEfNXhesAniJV)ofPaenibacillus polymyxa WLY78 encoding the nitrogenase enabled Escherichia coli to synthesize functional nitrogenase.The genome-wide transcriptional profiling of the recombinant E.coli 78-7 was examined for improving its nitrogenase activity.[Methods]The transcriptomic analysis of the recombinant E.coli 78-7 cultured under non-N_(2)-fixing(air and 100 mmol/L NH_(4)^(+))and N_(2)-fixing(without O_(2)and NH_(4)^(+))conditions was implemented.[Results]These results reveal that n/f genes were significantly transcribed under both conditions,indicating that the negative regulation of nifgene transcription by O_(2)and NH_(4)^(+)is bypassed in heterogeneous E.coli.The non-n/f genes specifically required for nitrogen fixation,such as mod,cys and feoAB encoding transporters of Mo,S,Fe and electron transporters,respectively,were transcribed at different levels in both conditions.The transcription levels of sufoperon and isc system specific for the synthesis of the Fe-S cluster varied greatly.The genes involved in nitrogen metabolism were notably up-regulated in N_(2)-fixing conditions.[Conclusion]These data suggest that the non-n/f genes specifically required for nitrogen fixation in recombinant E.coli had obvious effects on its expression of nitrogenase.Our results will provide valuable exploration regarding the improvement for nitrogenase activity of heterogeneous hosts.
基金supported by the National Natural Science Foundation of China(U21A20188,32071547)the Top‐Notch Young Talents Program(to Ximei Zhang)of China,and the Agricultural Science and Technology Innovation Program(to Ximei Zhang).
文摘Legumes play critical roles in agroecosystems by modulating nitrogen-fixing microorganisms to enhance soil fertility and promote crop productivity.Current research on the effects of legumes predominantly focuses on surface soil,lacking a comprehensive analysis of their overall impact across multiple soil layers and an in-depth understanding of associated microbial mechanisms.Here,the community structure of soil nitrogen-fixing microorganisms in three soil layers(0-20 cm,20-50 cm and 50-100 cm)under legume and non-legume cultivation was investigated through metagenomic sequencing.We found that only in topsoil(0-20 cm)legume treatment exhibited a significantly higher relative abundance of nitrogen-fixing genes than non-legume treatment.Under legume cultivation,the relative abundance of nitrogen-fixing genes was significantly higher in the topsoil layer than in deeper layers,whereas non-legume treatment displayed an inverse depth-dependent pattern.Combining soil physicochemical properties,the relative abundance of nitrogen-fixing genes correlated significantly with soil moisture,total carbon(TC),and dissolved organic carbon(DOC)content.Both TC and DOC were identified as key drivers of these genes.Subsequently,a similar depth-dependent pattern within the relative abundance of soil carbon degradation genes was found in response to the cultivation of both crops.The relative abundances of soil carbon degradation genes were negatively correlated with nitrogen-fixing genes under legume treatment individually,distinct from non-legume treatment.Our findings highlight the depth-dependent impact of legumes on nitrogen fixation and the critical interaction between soil carbon degradation and nitrogen fixation,providing insights into carbon management in legume cultivation practices to enhance nitrogen fixation in future agriculture.
