Salvaging high-quality genomes of microbial species from a meromictic lake using a hybrid sequencing approach

Most of Earth's bacteria have yet to be cultivated. The metabolic and functional potentials of these uncultivated microorganisms thus remain mysterious, and the metagenome-assembled genome (MAG) approach is the most robust method for uncovering these potentials. However, MAGs discovered by conventional metagenomic assembly and binning are usually highly fragmented genomes with heterogeneous sequence contamination. In this study, we combined Illumina and Nanopore data to develop a new workflow to reconstruct 233 MAGs-six novel bacterial orders, 20 families, 66 genera, and 154 species-from Lake Shunet, a secluded meromictic lake in Siberia. With our workflow, the average N50 of reconstructed MAGs greatly increased 10-40-fold compared to when the conventional Illumina assembly and binning method were used. More importantly, six complete MAGs were recovered from our datasets. The recovery of 154 novel species MAGs from a rarely explored lake greatly expands the current bacterial genome encyclopedia. Chen and colleagues develop a workflow for assembling high quality metagenome-associated genomes for microbial species using long and short reads, in this case from a meromictic lake. A full, detailed workflow is provided in for use by the community.

Automated summary

Chen and colleagues developed a workflow for assembling high quality metagenome-associated genomes for microbial species using both long and short reads. They successfully reconstructed 233 MAGs from a meromictic lake in Siberia, including six novel bacterial orders, 20 families, 66 genera, and 154 species. The quality of the reconstructed MAGs greatly improved using their workflow, with an average N50 increase of 10-40 fold, and recovery of six complete MAGs.