Diverse Mn(II)-Oxidizing Bacteria Isolated from Submarine Basalts at Loihi Seamount

Metal-oxidizing bacteria may play a key role in the submarine weathering of volcanic rocks and the formation of ferromanganese crusts. Putative fossil microbes encrusted in Mn oxide phases are commonly observed on volcanic glasses recovered from the deep ocean; however, no known Mn(II)-oxidizing bacteria have been directly identified or cultured from natural weathered basalts. To isolate epilithic Mn(II) oxidizing bacteria, we collected young, oxidized pillow basalts from the cold, outer portions of Loihi Seamount, and from nearby exposures of pillow basalts at South Point and Kealakekua Bay, HI. SEM imaging, EDS spectra and X-ray absorption spectroscopy data show that microbial biofilms and associated Mn oxides were abundant on the basalt surfaces. Using a series of seawater-based media that range from highly oligotrophic to organic-rich, we have obtained 26 mesophilic, heterotrophic Mn(II)-oxidizing isolates dominated by αand γ-Proteobacteria, such as Sulfitobacter, Methylarcula and Pseudoalteromonas spp. Additional isolates include Microbulbifer, Alteromonas, Marinobacter,