Isolate 761M: a New Type I Methanotroph That Possesses a Complete Tricarboxylic Acid Cycle

A methanotrophic bacterium, isolate 761M, grows slowly with methane as the sole carbon and energy source. Growth was stimulated by peptone, casein hydrolysate, glucose, and acetate plus malate. Sugars other than glucose did not stimulate growth. Growth yields, based on the amount of methane consumed, increased when other carbon sources were present, and less methane carbon was assimilated under these conditions. Methane was obligately required for growth of isolate 761M. This bacterium does not grow on rich media. Isolate 761M was found to possess hexulose phosphate synthase and intracytoplasmic membranes characteristic of other type I methanotrophs. Unlike other type I methanotrophs, this bacterium possessed alpha-ketoglutarate dehydrogenase and oxidized [2-C]acetate to carbon dioxide.