Bacterial diversity in a large, temperate, heavily modified river, as determined by pyrosequencing

Abstract

Despite the importance of microbes in lotic systems, the structure and diversity of microbial communities in rivers are understudied. Biodiversities of bacterial communities within a large, heavily modified river (Ohio River) and a major tributary (Guyandotte River) were examined using next-generation pyrosequencing and classical ecological diversity indices. Nextgeneration pyrosequencing was used to determine percent abundance of 16S rRNA gene sequences from 6 sites in the Ohio River and 1 site in the Guyandotte River. Cyanobacteria were the numerically dominant phylum (∼57%) in the Ohio River, suggesting a largely autochthonous community, and the community structure was unique relative to other aquatic and riverine systems. Multiple samples (n = 9) of the Ohio River communities had >85% similarity to one another on a sequence basis at the operational taxonomic unit level across several river kilometers, indicating the bacterial community of this river within a navigational pool is well mixed. The Guyandotte River community was only ∼13-20% similar to the Ohio River community and was dominated by Proteobacteria (∼75%), indicating a distinctly different bacterial community structure suggestive of allochthonous systems. The Guyandotte was more diverse than the Ohio River (Shannon diversity index: 4.23 and 2.29 respectively). Relative to lentic systems, the distribution of unique sequences at the phylum level were very similar, indicating that bacterial communities in both lotic and lentic systems are all composed of bacteria adapted to freshwater. © Inter-Research 2013.