Diversity and distribution of the lanthanome in aerobic methane-oxidising bacteria

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-oxidising 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, using proteomics to assess shifts in protein expression. This analysis uncovered several Ln-binding proteins, including the TonB-dependent receptors LanA and lutH, as well as Lanmodulin and LanP, with unique phylogenetic patterns. Metatranscriptomic data indicated active lanthanome expression, particularly in Proteobacteria, with the XoxF5 MDH variant prevalent in MOB genomes. The discovery of Ln-binding proteins on plasmids hints at 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 and offers potential biotechnological applications for Ln-dependent processes.