RESUMO
We present the draft genome sequence of Bradyrhizobium sp. strain Ce-3, which produced exopolysaccharide (EPS) and oxidized methanol in the presence of Ce3+. The genome for strain Ce-3 was estimated at 7,608,996 bp and showed that the strain is closely related to Bradyrhizobium erythrophlei MT12 and Bradyrhizobium sp. strain C9.
RESUMO
Lanthanide (Ln)-dependent XoxF-type methanol dehydrogenase (MDH) genes can be found in bacteria that are not believed to be methylotrophs, and studies on their methylotrophic pathways and their use of Ln are now emerging. Ln-dependent methanol utilization in Bradyrhizobium sp. strain Ce-3, which belongs to the Bradyrhizobium elkanii superclade (clade II), was investigated in this study. Strain Ce-3 was able to grow in a media containing methanol as a sole carbon source and light Ln (L-Ln, i.e., La3+, Ce3+, Pr3+, and Nd3+), whereas the strain did not show any growth with Ca2+ or the heavy Ln, Sm3+. We found that the uptake of L-Ln is enhanced mainly by methanol and L-Ln species, and the strain incorporates each L-Ln species evenly into the cell. The genome of strain Ce-3 encodes the xox cluster for Ln-dependent methanol dehydrogenase (xoxF) and the enzymes participating in the methanol oxidation pathway (xoxG, fldA, and gfaA) and regulation (xoxR), but the gene encoding formate dehydrogenase (FDH) was not found in the cluster. MDH, formaldehyde dehydrogenase, and FDH activities were induced by methanol/Ln. Moreover, expression of the genes on the xox cluster was upregulated by methanol/Ln. Based on these results, we concluded that strain Ce-3 possesses a complete L-Ln-dependent methanol oxidation pathway, which is dissimilar to plant phyllospheric bacteria, Methylobacterium species, with a transport system for L-Ln species.