Response of Prokaryotes to TOC Contamination in Dianchi Lake Sediments

Abstract

Background: Explaining microbial consortia in sediments from the perspective of taxon, co-occurrence and function is the key to recover and maintain aquatic ecosystems. Trophic status was widely considered to be an important determinant of the lake sediment microbial community. However, little is known about the effect of a special eutrophic factor gradient on the prokaryotic community structure in situ. Within this context, we explored prokaryotic communities using an intensive field sampling from sediments in the Dianchi Lake, one of the most eutrophic lakes in China. Results: Microbial assemblages was strongly correlated with total organic carbon (TOC). Moreover, relatively high and low TOC shaped taxonomic and functional differences in microbial assemblages. The results identified the most abundant bacteria across all samples as Proteobacteria , Nitrospirae , Chloroflexi , Firmicutes , Ignavibacteriae , Actinobacteria , Bacteroidetes , Acidobacteria , Spiprochaetae and Latescibacteria . The dominant groups of archaea were Euryarchaeota , Woesearchaeota DHVEG-6 , Bathyarchaeota and WSA2 . Low TOC (LT) microbial assemblages displayed a major proportion of functional profiles related to some metabolisms such as carbohydrate metabolism, amino acid metabolism, energy metabolism, nucleotide metabolism and metabolism of cofactors and vitamins, membrane transport. These results illustrated that TOC concentration had obvious influence on the relative abundances of KEGG orthologs . Finally, the meta-analysis results highlight that most of network parameters of the LT community were significantly greater than those of other communities, which suggesting that the LT community was larger and more complex. Conclusion: TOC level might be a key determinant to shape taxonomic and functional construction of communities in Dianchi Lake sediment. LT community tended to establish a larger and more complex co-occurrence, which suggested that they may interact with each other strongly and exchange essential metabolites. Overall, this study could enhance our knowledge of microbial assemblages in eutrophic lake sediment and provide clues for the restoration and maintenance of sediment ecosystems.