Magnetosome gene cluster containing bacteria in oxygen-stratified freshwater ecosystems of northern landscapes

Magnetotactic bacteria (MTB) are capable of magnetic navigation (magnetotaxis) through the intracellular biomineralization of membrane-bound magnetic nanoparticles, known asmagnetosomes, which are regulatedby magnetosome gene clusters (MGCs). Despite their ubiquitynear the oxic-anoxic transition zone in various aquatic environments, the diversity, abundance, and biogeochemical roles of MTB remain poorly understood due to limitedlarge-scale studies. Here,we conducted a metagenomic survey of MGC-containing bacteriaacross 38 oxygen-stratified freshwater environments of northern landscapes. We reconstructed 63 MGC-containing genomes affiliated with eight bacterial phyla, including Myxococcota. PutativeMTBexhibited high relative abundance(up to 15.4% of metagenomic reads), with Deltaproteobacteria identified as the most ubiquitous and predominantgroup. Vertical distribution profile revealed that magnetotactic Deltaproteobacteria primarily inhabit low-oxygen niches, suggesting their magnetofossils might serve as a potential proxy for oxygen depletion. Our findings underscore the significant ecological roles of putativeMTB as key components of oxygen-stratified freshwaterecosystemsof northern landscapes.