Bacterial contributions to the formation of polymetallic nodules in the Pacific Ocean

Polymetallic nodules, widely distributed in the deep seafloor of the Pacific Ocean, are characterized by their abundance of diverse metal elements and considerable economic value. Previous studies have suggested a partial biogenic origin of these nodules. This study investigated the role of microorganisms in nodule formation by examining biological-like structures and bacterial communities within nodules and sediments. Scanning electron microscopy revealed bacteria-like microspheres, skeleton-like structures and extracellular polymeric substances-like structures in the nodules. Energy dispersive spectroscopy showed that these biological-like structures facilitated metal enrichment, enabling subsequent mineral precipitation. Shewanella, Colwellia, Leptospirillum, Sulfitobacter, and other bacteria may possess mineralization potential due to their Mn or Fe oxidation capabilities. Differences in internal structures and bacterial community composition between nodules from the western and eastern Pacific Ocean could potentially suggest that growth environment factors may contribute to nodule formation variation. These findings highlight the involvement of microorganisms in nodule formation and contribute to a better understanding of the biogenic mineralization process.