Global Distribution and Biogeochemical Significance of Magnetotactic Bacteria in Deep‐Sea Cold Seep Ecosystems

Magnetotactic bacteria (MTB) are distinguished by their ability to navigate along Earth's magnetic field and form diverse intracellular minerals, including nanocrystals of magnetite or greigite (i.e., magnetosomes). Although MTB are widespread in oxic‐anoxic transition zones of aquatic systems worldwide, their presence in deep‐sea environments has been less explored largely due to challenges in sampling and analytical methods. Here, we investigated deep‐sea sediments from two active cold seeps in the South China Sea using metagenomic, magnetic, and microscopic techniques and extended our study to a global‐scale metagenomic analysis of cold seep ecosystems. Our results reveal a wide distribution and high phylogenetic diversity of MTB in cold seeps worldwide with the phylum Desulfobacterota being particularly prevalent. Genome‐scale metabolic reconstructions suggest that MTB contribute to iron and sulfur cycling potentially coupled with anaerobic methane oxidation in these deep‐sea habitats. These findings not only broaden our understanding of MTB diversity and distribution in the deep sea but also underscore their important roles in biogeochemical processes within cold seep ecosystems.