Metagenomic Assembled Genomes of a Pseudanabaena Cyanobacterium and Six Heterotrophic Strains from a Xenic Culture

Sequencing cyanobacteria from xenic cultures is often challenging when their DNA extracts are confounded by DNA from their heterotrophic microbiome. Using an iterative DNA lysis protocol can fractionate between DNA from the cyanobacterium and the heterotrophic strains. To further demonstrate the utility of this protocol, it was used to sequence another xenic culture of cyanobacteria. This effort led to the assembly of a megabase-length cyanobacterial chromosome; however, repeated ribosomal regions created assembly issues even after adding data from another sequencing run to improve coverage. A separate DNA preparation from a single cell lysis step was also run for comparison but yielded a markedly lower proportion of cyanobacterial reads (<2%). Instead, the circular cyanobacterial chromosome was closed with targeted amplicon sequencing. Phylogenetic analysis assigned this strain to the genus Pseudanabaena. Within the metagenomic assembly were the genomes of six heterotrophic strains, preliminarily assigned as belonging to the genera Acidovorax, Hydrogenophaga, Lysobacter, Novosphingobium, Sediminicoccus, and Tabrizicola. Lysobacter sp. BL-A-41-H3’s chromosome was also assembled as a closed circular contig. This study demonstrates that iterative lysis enriches for cyanobacterial DNA and enables concurrent genome assembly of cohabitating heterotrophs alongside the host cyanobacterium.