Efficient Counterselection for Methylococcus capsulatus (Bath) by Using a Mutated pheS Gene

Methanotrophs have long been considered promising strains for biologically reducing methane from the environment and converting it into valuable products, because they can oxidize methane at ambient temperatures and pressures. Although several methodologies and tools for the genetic manipulation of methanotrophs have been developed, their mutagenic efficiency remains lower than that of tractable strains such asEscherichia coli . Therefore, further improvements are still desired. The significance of our study is that we increased the efficiency of counterselection inM. capsulatus (Bath) by employingpheS *, which was newly constructed as a counterselectable marker. This will allow for the efficient production of gene-disrupted and gene-integrated mutants ofM. capsulatus (Bath). We anticipate that this counterselection system will be utilized widely by the methanotroph research community, leading to improved productivity of methane-based bioproduction and new insights into methanotrophy.