Lanthanide-dependent enzyme and motility in plant-associating methylotrophic bacteria
Plant emit large quantities of methanol through stomata as a result of their growth and pectin degradation. Methanol can be a good nutrient for bacteria and methanol-utilizing (methylotrophic) bacteria predominate on the aerial plant surface (phyllosphere). We focus on their methanol metabolism and symbiosis with plants.
Methylobacterium species are commonly found in phyllosphere, and they can promote plant growth. They have methanol dehydrogenase (MDH) to oxidize methanol. Not only calcium-dependent MDH encoded by mxaF, recently it was found that lanthanide-dependent MDH is also encoded by xoxF in the genomes of Methylobacterium species. This is the first enzyme described to date, to contain lanthanide. We investigate the mechanism of expression switching between these MDHs, depending on the availability of lanthanide.
We also study molecular mechanism of the motility and chemotaxis in methylotrophs, which is important for the bacteria to find and colonize plants. The chemotaxis is also affected by the carbon source and lanthanide.
We have found new methylotrophic bacteria belonging to novel genera. They have been isolated from rice rhizosphere using lanthanide as an essential cofactor. They are named as Oharaeibacter diazotrophicus SM30 and Novimethylophilus kurashikiensis La2-4. Thus, lanthanide can be used for isolation of bacteria that contain xoxF, which can be found in many so-believed non-methylotrophic bacteria and novel bacteria.