Sources Of Organic Matter Affect Microbial Community Composition In Sediment Of Lake Erhai

To evaluate whether different deoxyribonucleic acid (DNA) extraction procedures can affect estimates of bacterial community composition, based on the 16S ribosomal ribonucleic acid gene denaturing gradient gel electrophoresis (DGGE) profiles, we compared the effect of DNA extraction methods on vertical microbial community profiles in sediment, and investigate the relationships between vertical distribution of bacterial community and environment variables, especially the source of organic matter. PCR-denaturing gradient gel electrophoresis (DGGE), stable carbon isotope (δ13C), C/N atomic ratio and canonical correspondence analysis (CCA) were used in this study. Bacteria community composition (BCC) exist in natural environment was characterized by DGGE of 16S rRNA gene with subsequent sequencing. Our results demonstrated that the choice of DNA extraction method significantly influenced the bacterial community profiles generated, but DNA extraction method did not affect the evaluation of the relationship between bacterial community structure and environmental variables in lake sediment at multiple depths. Significant differences were also observed between the two methods with respect to DNA yields from the deeper (10-44 cm) samples (p<0.05). CCA revealed depth-related variation in sediment bacterial community in different areas of the lake were significantly influenced by different environmental factors, however, OM source played important roles in structuring BCC at all sites. The DGGE banding patterns revealed that abundance of the δ-Proteobacteria decreased accompany with the proportion of C4 plant-derived organic carbon elevated. Sequencing of DGGE bands suggested that the majority of the sequences were affiliated with common phylogenetic groups in lake sediment:Chloroflexi, Deltaproteobacteria and Firmicutes. Betaproteobacteria detected in our study were appeared as prominent phylotype in upper sediment. BCC suggested that the trophic state of northern zone is much higher than other areas of Lake Erhai. Shannon-Wiener diversity index and function of bacterial community was directly affected by OM source, constant OM source resulted in stable higher diversity of bacterial community and broader enzymatic capabilities to access OM. We can conclude that differences in diversity and function of bacterial community in samples differing in their source of OM were followed in relation to environmental variables. Our study showed insights into relationships between natural BCC and OM source, facilitating a better understanding of microbial community structure and ecosystem function in the lake sediment.