LAUSR

Methylotrophic bacteria use methanol and related C1-compounds as carbon and energy source. Methanol dehydrogenases are essential for methanol oxidation, while lanthanides are important co-factors of many pyrroloquinoline quinone dependent methanol dehydrogenases and related alcohol dehydrogenases. We describe here the physiological and genomic characterization of newly isolated Beijerinckiaceae bacteria that rely on lanthanides for methanol oxidation. A broad physiological diversity was indicated by the ability to metabolize a wide range of multi-carbon substrates, including various sugars, and organic acids, as well as diverse C1-substrates such as methylated amines and methylated sulfur compounds. Methanol oxidation was only possible in the presence of low mass lanthanides (La, Ce, Nd) in submicromolar concentrations (> 100 nM). Compared to other Beijerinckiaceae, genomic and transcriptomic analyses revealed the usage of a glutathione and tetrahydrofolate dependent pathway for formaldehyde oxidation and channeling methyl groups into the serine cycle for carbon assimilation. Besides a single xoxF gene, we identified two additional genes for lanthanide-dependent alcohol dehydrogenases, among them one coding for an ExaF-type alcohol dehydrogenase, which was so far not known from Beijerinckiaceae. Homologs for most of the gene products of the recently postulated gene cluster linked to lanthanide utilization and transport could be detected, but it remains unanswered for now how lanthanides are sensed and taken up by our strains. Studying physiological responses to lanthanides under non-methylotrophic conditions in these isolates as well as other organisms is necessary to gain a more complete understanding of lanthanide-dependent metabolism as a whole. Importance: We supplemented the broad metabolic diversity of the Beijerinckiaceae by characterizing new members of this family that rely on lanthanides for methanol oxidation and that possess additional lanthanide-dependent enzymes. Considering that lanthanides are critical resources for many modern applications and that recovering them is expensive and heavy on the environment, lanthanide-dependent metabolism in microorganisms is an exploding field of research. Further research into how the isolated Beijerinckiaceae and other microbes utilize lanthanides is needed to increase our understanding of lanthanide-dependent metabolism. The diversity and widespread occurence of lanthanide-dependent enzymes makes it likely that lanthanide utilization varies in different taxonomic groups and is dependent on the habitat of the microbes.