Study On Bacterial Community Structure,Co-occurrence Pattern And Assembly Process In Caohai,Guizhou

Lake bacterial communities are an important component of water ecosystems and have direct or indirect effects on the material and energy cycles of water ecosystems.Epiphytic bacterial communities(EBC)planktonic bacterial communities(PBC)and benthic bacterial communities(BBC)are all important to the biogeochemical processes in freshwater lakes.However,the community diversity,interspecies interactions and community assembly mechanisms of lake bacterial communities are not well understood.The objectives of this study were to investigate the temporal evolutionary characteristics of epiphytic bacterial communities in lakes at different times,seasonal differences in bacterial communities in different media,and the main environmental factors affecting bacterial communities.A 16 S r RNA gene high-throughput sequencing method was used to sequence 83 water,sediment and two epiphytic biofilm samples collected from July to November in Caohai,Guizhou,China.The community structures of epiphytic,planktonic and benthic bacteria were analyzed;the interaction patterns of different bacterial communities were explained by phylogenetic molecular ecological network analysis;and the relative importance of deterministic and stochastic factors in bacterial communities was elucidated by statistical methods based on the null model.Overall,this work is expected to improve the understanding of bacterial communities in lakes.The following conclusions were obtained from the study:(1)Water temperature was significantly lower(p < 0.001)from July(18.1± 0.3?)to November(9.5 ± 1.2?).NH₄⁺-N,TP,and p H were significantly higher in July than in October and November.Chl a and SD were not significantly different in the water column between periods(wilcox test,p > 0.05).(2)The two species had similar epiphytic bacterial community composition.The community structure of the epiphytic bacterial communities showed a clear temporal succession.The differences in epiphytic bacterial community diversity may be closely related to the process of epiphytic biofilm development.Gammaproteobacteria were the dominant species in both bacterial communities of different media.The abundance(Chao1 index)and community diversity(i.e.,phylogenetic diversity and Shannon diversity)of epiphytic bacterial communities were significantly different among months(p < 0.05).There was no significant difference in community richness(Chao1index)and Shannon diversity index between planktonic and benthic bacterial communities in different months(p > 0.05).The bacterial community richness(Chao1 index)and community diversity(i.e.,phylogenetic diversity and Shannon diversity)were significantly different between media(Wilcoxon test,p < 0.05).(3)Non-metric multidimensional scaling(NMDS)analysis showed that epiphytic bacterial communities and planktonic bacterial communities showed significant seasonal variation in ?-diversity across seasons.There was no significant seasonal variation in benthic bacterial communities,but benthic bacteria were significantly different in the upstream and downstream(p < 0.05).The results of redundancy analysis(RDA)and Mantel test correlation analysis showed that WT was the most influential environmental factor on the bacterial community.(4)The network co-occurrence patterns of bacterial communities in different seasons showed that the connectivity and complexity of the co-occurrence patterns of epiphytic bacterial communities gradually increased with time.the network co-occurrence patterns of epiphytic bacterial communities were more complex and had more key species in October and November than in other months.the complexity of the network co-occurrence patterns of planktonic bacterial communities was higher in November than in July.The benthic bacterial community network did not differ significantly from season to season and had a strong seasonal stability in topological characteristics.Gammaproteobacteria,Alphaproteobacteria and Actinobacteria were the main common species contained in the different media bacterial community networks.(5)Zero model analysis showed that epiphytic bacterial community construction was mainly controlled by heterogeneous selection(?NTI>+2)(57%).This was followed by dispersal limitation(-2+2)(33.3%),dispersal limitation(-2+2)(56.7%),dispersal limitation(-2