Plos one_Comparative genomic analysis of Methylocystis sp. MJC1 as a platform strain for polyhydroxybutyrate biosynthesis

Methane is a potent greenhouse gas with the potential to cause global warming higher than that of carbon dioxide. It is also an important industrial chemical by being a primary component of natural gas and biogas. The chemical conversion of methane into other chemicals requires a high amount of energy due to the high activation energy of the carbon-hydrogen bond. Methanotrophs, on the other hand, can produce various products without requiring such high energy inputs. Polyhydroxybutyrate (PHB) is one of the promising biodegradable plastics. Type II methanotrophs have been known to produce PHB from methane. For the industrial application of PHB production from methane by methanotrophs, isolation, characterization and genome analysis of many methanotrophic strains are prerequisites for industrial strain development and further metabolic engineering for enhanced PHB productivity. This study presents the comparative genomic analysis of a newly isolated methanotroph, <em>Methylocystis</em> sp. MJC1 is a biodegradable PHB-producing platform strain. <em>Methylocystis</em> sp. MJC1 accumulates up to 44.5% of PHB based on dry cell weight under nitrogen-limiting conditions. To facilitate its development as a PHB-producing platform strain, the complete genome sequence of <em>Methylocystis </em>sp. MJC1 was assembled, functionally annotated, and compared with genomes of other <em>Methylocystis</em> species. Comparative genomics analysis was done to assess <em>Methylocystis </em>sp.<em> MJC1</em> in the context of other <em>Methylocystis clade</em> strains. These comparative analysis would open the possibility of future practical applications such as the development of organism-specific genome-scale models and application of metabolic engineering strategies to <em>Methylocystis </em>sp. MJC1.