Geochemically Relevant Molybdenum Sources for Nitrogen Fixing Methanogens

ABSTRACT: Molybdenum (Mo) is a key component of several metallocofactors in methanogen enzymes, including formate dehydrogenase (Fdh), formylmethanofuran dehydrogenase (Fmd), and molybdenum-nitrogenase (Nif). Molybdate oxyanion (MoO42-) has long been considered the only bioavailable form of Mo to biology. However, in anoxic and sulfidic (euxinic) habitats typically inhabited by methanogens and other anaerobes, Mo is found as soluble tetrathiomolybdate (MoS42-) ions and insoluble molybdenite (MoS2) mineral. Here, we show that the methanogen, Methanococcus maripaludis, can grow formatotrophically and diazotrophically (conditions that require Fdh, Nif, and Fmd) with MoS42- and MoS2. Cells grew as well or better with MoS42- and MoS2 when compared to growth with MoO42-. Cells grown with MoS42- and MoO42- have similar Mo contents, implying efficient means for acquiring both forms of Mo. Yet, transcriptomes of MoS42-- and MoO42--grown cells reveal minimal differences in the expression of Mo-dependent enzymes, biosynthesis proteins, and transporters, including three homologs of the putative MoO42- transporter, Mod. This may suggest overlap in mechanisms of acquiring and trafficking of MoO42- and MoS42- prior to their use in the iron-molybdenum cofactor (Nif) and molybdopterin cofactor (Fdh, Fmd). Direct contact between cells and MoS2 was stimulatory relative to growth supported solely by abiotic dissolution, indicating yet to be defined mechanisms for enhanced MoS2 dissolution. Together, these results suggest that thiolated forms of Mo (MoS42- and MoS2) that predominate in modern anoxic and euxinic habitats and that were pervasive prior to Earth’s oxygenation can support the Mo demands of methanogens and possibly other anaerobic microorganisms.

ORGANISM(S): Methanococcus maripaludis

PROVIDER: GSE261517 | GEO | 2024/07/12

REPOSITORIES: GEO