Characterizing of novel magnetotactic bacteria using a combination of magnetic column separation (MTB-CoSe) and mamK-specific primers

Magnetotactic bacteria (MTB) belong to different taxonomic groups according to 16S rRNA or whole-genome phylogeny. Magnetotactic representatives of the class Alphaproteobacteria and the order Magnetococcales are the most frequently isolated MTB in environmental samples. This bias is due in part to limitations of currently available methods to isolate MTB. Here we describe a new approach for isolation of MTB cells that does not depend on cell motility and will allow collecting bacteria both south- and north-seeking movement. We also designed a specific primer system for the gene encoding the MamK protein that effectively detects diverse MTB phylogenetic groups in any sample type. The combination of these two approaches allowed the identification of a novel MTB belonging to the family Syntrophaceae of the class Deltaproteobacteria. Moreover, we found that Nitrospirae bacteria predominated in the MTB fraction of a sample taken from Lake Beloe Bordukovskoe near Moscow, Russia. We describe the novel dominant Nitrospirae bacterium 9Candidatus Magnetomonas plexicatena9 and propose its taxonomic name.