查看更多>>摘要：Coastal ecosystems are an important region for biogeochemical cycling,are a hotspot of anthropogenic disturbance and play a crucial role in global carbon cycling through the metabolic activities of bacterioplankton.Bacterioplankton can be broadly classified into two lifestyles:free-living(FL)and particle-attached(PA).However,how coastal bacterioplankton the com-munity structure,co-occurrence networks and carbon metabolic functions with different lifestyles are differentiated is still largely unknown.Understanding these processes is necessary to better determine the contributions of coastal bacterioplankton to carbon cycling.Here,the characteristics of community structure and carbon metabolism function of bacterioplankton with two lifestyles in the coastal areas of Guangdong Province were investigated using amplicon sequencing,metagenomic,and metatranscriptomic techniques.The results show that the main bacterioplankton responsible for carbon metabolism were the Pseudomonadota,Bacteroidota,and Actinomycetota.The microbial community structure,carbon metabolic func-tion,and environmental preferences differ between different lifestyles.FL and PA bacteria exhibited higher carbon fixation and degradation potentials,respectively.A range of environmental factors,such as dissolved oxygen,pH,and temperature,were associated with the community structure and carbon metabolic functions of the bacterioplankton.Human activities,such as nutrient discharge,may affect the distribution of functional genes and enhance the carbon degradation functions of bacterioplankton.In conclusion,this study increased the understanding of the role of microorganisms in regulating carbon export in coastal ecosystems with intense human activity.
查看更多>>摘要：Phosphorus concentration on the surface of seawater varies greatly with different environments,especially in coastal.The molecular mechanism by which cyanobacteria adapt to fluctuating phosphorus bioavailability is still unclear.In this study,transcriptomes and gene knockouts were used to investigate the adaptive molecular mechanism of a model coastal cyano-bacterium Synechococcus sp.PCC 7002 during periods of phosphorus starvation and phosphorus recovery(adding sufficient phosphorus after phosphorus starvation).The findings indicated that phosphorus deficiency affected the photosynthesis,ribosome synthesis,and bacterial motility pathways,which recommenced after phosphorus was resupplied.Even more,most of the metabolic pathways of cyanobacteria were enhanced after phosphorus recovery compared to the control which was kept in continuous phosphorus replete conditions.Based on transcriptome,54 genes potentially related to phosphorus-deficiency adaptation were selected and knocked out individually or in combination.It was found that five mutants showed weak growth phenotype under phosphorus deficiency,indicating the importance of the genes(A0076,A0549-50,A1094,A1320,A1895)in the adaptation of phosphorus deficiency.Three mutants were found to grow better than the wild type under phosphorus deficiency,suggesting that the products of these genes(A0079,A0340,A2284-86)might influence the adapta-tion to phosphorus deficiency.Bioinformatics analysis revealed that cyanobacteria exposed to highly fluctuating phosphorus concentrations have more sophisticated phosphorus acquisition strategies.These results elucidated that Synechococcus sp.PCC 7002 have variable phosphorus response mechanisms to adapt to fluctuating phosphorus concentration,providing a novel perspective of how cyanobacteria may respond to the complex and dynamic environments.
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