Project description:Lanthanides (Ln) play essential roles in the metabolism of certain bacteria, catalysing key reactions in methane oxidation. This study investigates the diversity and distribution of Ln-dependent proteins, collectively termed the lanthanome, in aerobic methane-oxidizing bacteria (MOB) using genome, plasmid, and metatranscriptome data from methane-rich lake sediments. A custom database of 180 MOB genomes revealed various methanol dehydrogenase (MDH) isoforms, including XoxF variants, distributed across Proteobacteria and Verrucomicrobia phyla. We conducted an experimental study with Methylosinus trichosporium OB3B exposed to CeCl₃ and an ore containing mixed lanthanides, measuring methane oxidation rates and using proteomics to assess shifts in protein expression. Despite differences in adaptation times, methane oxidation rates were consistent across treatments, indicating similar overall metabolic efficiencies after acclimatisation. The genomic analysis uncovered several Ln-binding proteins, including the TonB-dependent receptors LanA and lutH-like, as well as Lanmodulin and LanPepsy, with unique phylogenetic patterns. Metatranscriptomic data showed active lanthanome expression, particularly in Proteobacteria, with the XoxF5 MDH variant prevalent in MOB genomes. The discovery of Ln-binding proteins in plasmids suggests potential horizontal gene transfer, highlighting adaptive mechanisms of MOB to Ln availability and their ecological role in methane cycling. This work expands our understanding of Ln-utilising bacteria, particularly in the context of lanthanide-driven methane oxidation, and offers potential biotechnological applications for Ln-dependent processes.
