GUANINE PLUS CYTOSINE DNA CONTENT OF PSYCHROPHILIC METHANOTROPH AND ITS DNA - DNA HYBRIDIZATION WITH METHANOTROPHS OF TYPE-1

Obligate methanotrophs are unique microorganisms utilizing methane or methanol as a sole carbon and energy source. In 1970 Whittenbury et al . isolated more than 100 strains of methanotrophs and classified them in five groups: Methylomonas, Methylobacter, Methylococcus, Methylocys tis, and Methylosinus [1] with the status of genera [2, 3], but only M ethylomonas and Methylococcus have been validated. In 1981, Romanovska ya suggested including the Methylobacter group in the genus Methylococ cus and this inclusion was validated [4, 5]. However, in 1991 due to i ts heterogeneity the genus Methylococcus was subdivided into two clust ers of methylococci with low and high guanine-plus-cytosine (G + C) co ntent of DNA [6]. The analysis of 5S RNA sequences also confirmed a re asonable arrangement of methanotrophs into five groups [7].