Detection, isolation and characterization of marine methanotrophs

Abstract

In order to investigate the occurrence of methanotrophs in the marine environment, representative organisms have been isolated from seawater. As traditional methods for isolating and cultivating methanotrophs were found to be unsuccessful when applied to the marine environment, new techniques for methanotroph isolation were developed. These were used to enrich for methanotrophs in several marine areas. Two bacteria isolated from marine areas have been extensively characterized. Both isolates appear to be typical of Type I methanotrophs and have an absolute requirement for sodium chloride. The nitrogen assimilation of the isolates was studied in detail. Both isolates appear to have unusual nitrogen assimilation pathways. A method for detecting methylotrophs and methanotrophs without cultivation has also been developed. The polymerase chain reaction has been adapted to amplify DNA sequences specific to methylotro~ls and methanotrophs. This has been used to detect amplify DNA sequences in DNA extracted from water samples from a range of fresh water and marine environments. The methods has been demonstrated to be specific for methylotrophic and methanotrophic DNA. DNA from non-methylotrophic bacteria was not amplified. Initial studies on the application of this method for enumeration has also been studied. An investigation into the occurrence of methanotrophs in the Southern Ocean was also carried out. Methanotrophic activity was examined in two areas of the Southem Ocean. This was compared with the methane concentration in the water and total bacterial activity