Plasmids in methanotrophic bacteria: isolation, characterization and DNA hybridization analysis.

Ten strains of obligate methanotrophs were screened for the presence of plasmid DNA using a variety of methods. Plasmids were detected in all strains except Methylococcus capsulatus Bath. No significant similarity between plasmids was observed with respect to size or restriction digest patterns except for three strains of Methylosinus trichosporium, which appeared to contain the same three plasmids. Nitrocellulose filter hybridization revealed that the plasmid DNA from the M. trichosporium strains shared a small region of homology with the plasmid DNA from Methylosinus sporium 5. All of the plasmids remain cryptic. As the first step in characterization, a restriction digest map of the 55 kb plasmid found in Methylomonas albus BG8 was constructed.