Analysis Of Microbial Interspecies Relationships Based On The Properties Of B Vitamins Synthesis And Utilization

B Vitamins(VB)is the general name of a variety of water-soluble vitamins involved in many important biochemical reactions,in which VBS are used as the enzyme cofactors.In recent years,however,genomics and biochemical analysis has shown that many microorganisms cannot synthesize certain vitamins de novo due to the absence of genes,even though they contain the enzymes which require them.The physiological metabolism or ecological function of these VB-defective microorganisms must depend on exogenous vitamins or similar precursor molecules.Therefore,the interactions between different microorganisms may be established through the interspecies transfer of vitamins,which may play an important role in the formation and function of microbial community.The microorganisms in lake play important roles in ecosystem balance and biogeochemical cycle of important elements.However,the relationship between the interspecies interaction of lake microorganisms and the characteristics of vitamin synthesis and utilization has not been fully understood.Based on the microbiome data of the Nanhu lake in Wuhan city,this study investigated the synthesis and utilization properties of important VB by various microorganisms according to the genome analysis,and investigated the network of VB transmission among microbial species when combined with species co-occurrence analysis results.The main results of this study are as following:(1)Genomic sequences and annotations of 9276 microorganisms were downloaded from IMG and were used for assessing their ability of B vitamins biosynthesis and dependence.The top 5 phylums of the genomics are:proteobacterwia(2,276 strains),firmicutes(780 strains),bacteroides(592 strains),Parcubacteria(495 strains)and actinomycetes(373 strains).In these microorganisms,the percentages of B vitamins synthesizing strains are:VB1(33.99%),VB2(50.55%),VB3(31.32%),VB5(39.13%),VB6(9.81%),VB7(21.71%),VB9(31.82%)and VB1:(12.10%),respectively;the percentages of B vitamins depending strains are:VB1(97.13%),VB2(100%),VB3(100%),VB5(95.15%),VB6(97.84%),VB7(65.67%),VB9(62.94%)and VB12(88.29%),respectively.(2)Analysis of vitamin synthesis and utilization properties in the microbial community of Nanhu lake,Wuhan.Depending on the 16S rRNA gene sequencing data of water samples from Nanhu Lake,we searched the most similar genomes from NCBI and IMG databases.The percentages of B vitamins synthesizing strains are:VB1(69.05%),VB2(88.49%),VB3(75.12%),VB5(90.98%),VB6(35.30%),VB:(60.34%),VB9(54.43%)and VB12(31.10%),respectively;the percentages of B vitamins depending strains are:VB1(99.84%),VB2(100%),VB3(100%),VB5(99.84%).VB6(99.84%),VB7(99.53%),VB9(94.71%)and VB12(99.84%),respectively.(3)We calculated the co-occurrence patterns between OTUs using SparCC method.The resulted network contained a total of 443 OTUs,among which the top 5 phyla aree proteobacteria(174 OTUs),bacteroides(112 OTUs),actinomycetes(65 OTUs),cyanobacteria(48 OTUs)and firmicutes(10 OTUs).OTU3213,a Microcystis,is an important node in the network since it has the highest degree centrality,the highest closeness centrality and the next higher betweenness centrality.(4)Analysis of VB transmission network among microbial species.The contribution of B vitamins to the microbial co-occurrence network was determined by the genomic search,annotation of each node OTUs in the network and the complementarity of OTUs'synthesis and dependence on B vitamins.By analyzing the topological structure of each B vitamin co-occurrence networks and the whole B vitamins co-occurrence networks,we attempted to explain the contribution of B vitamins in the formation of microbial communities.It was found that 26.21%of microbial interactions may involve the transfer of B vitamins.Taken together,by means of studying the characteristics of the synthesis and utilization of B vitamins in lake microorganisms we partially explained the important role of interspecies transfer of B vitamins in the formation of microbial community structure.to the results would be helpful for a better understanding of the mechanisms involved in the formation and succession of microbial communities,and lays a foundation for the construction and maintenance of microbial communities in production.