Ecophysiological and Genomic Characterization of Methylotrophic Bacteria belongting to the LD28 Clade from Lake Soyang

초록

Methylotrophs in freshwater can play a substantial role in the global carbon cycle although they only exist regionally. Many members of the methylotrophic bacteria have been isolated from aquatic environments, however major freshwater methylotrophic clade such as the LD28 clade do not have any cultured representatives and its marine counterpart clade, the OM43 clade, has only small number of isolates such as HTCC2181. The LD28 clade of the family Methylophilaceae is a betⅣ subclass of betaproteobacteria widely found in freshwater environments. Here we report cultivation and genome sequencing of strain IMCC19250, chosen as a representative strain among 59 bacterial strains belonging to the LD28 clade, cultured from Lake Soyang using High-Throughput cultivation. We found that the strain IMCC19250 is an obligate methylotroph with C1 metabolic pathways showing cellular growth depending on methanol, yielding 24.2μM. Optimum growth was observed at 30℃, pH7, and in the presence of 0.1% of NaCl. The genome of this strain contains a circular chromosome of 1,310,153 bp and the overall G+C content of the chromosome is 36.63%. It includes genes for rhodopsins, but no difference in growth was observed under light and dark conditions. Through comparative genomic analysis, we could find the clue that IMCC19250 and OM43 strains originated from the same ancestor.