Characterization of Freshwater Microbial Community of Lake Soyang by Shotgun Metagenome Sequencing of Seasonal Samples

초록

Lake Soyang is the largest reservoir in Korea. In a previous study based on 16S rRNA gene amplicon sequencing, the bacterial assemblage of Lake Soyang exhibited seasonal and depth-dependent variation. In this study, to understand the microbial community structure of Lake Soyang more thoroughly, we analyzed shotgun metagenomes for 8 water samples collected from two depths (1 m and 50 m) for four seasons. Metagenome sequencing yielded an average of 16 Gbp (64 million reads; 250-bp paired end) for each sample. Taxonomic profiling by MetaPhlAn showed the prevalence of the acI lineage and the LD12 clade and also revealed bacterial community shift following summer stratification and winter mixing, which were congruent with the results from 16S rRNA gene amplicon sequencing. Metagenome assembly by SPAdes produced more than 1.6 million contigs of 1 kb or more. Contig binning by MaxBin resulted in 224 metagenome assembled genomes (MAGs) of ≥90% completeness. The sizes and GC contents of the 224 MAGs ranged 1.36?7.85 Mbp and 31.5?70.8%, respectively. Fragment recruitment of the metagenome sequences was performed using the complete genome sequences of the four acI strains (previously isolated from Lake Soyang) and the results showed specific distribution patterns of the acI sub-clades. [This study was supported by a grant of the Mid-Career Research Program through the NRF.]