Mechercharimyces mesophilus gen. nov., sp. nov. and Mechercharimyces asporophorigenens sp. nov., antitumour substance-producing marine bacteria, and description of Thermoactinomycetaceae fam. nov.

A study was carried out to clarify the taxonomy of four Gram-positive, heterotrophic mesophiles isolated from marine lakes in the Republic of Palau. The strains, designated YM3-251(T), YM3-653, YM3-671 and YM11-542(T), formed aerial and substrate mycelia. The cell-wall peptidoglycan contained meso-diaminopimelic acid, glutamic acid and alanine. The G+C content of their genomic DNA was approximately 45 mol%. The major fatty acid was iso-C(15 : 0) and the major isoprenoid quinone was MK-9. The strains formed a distinct group in the 16S rRNA gene tree and shared a range of phenotypic properties that distinguished them from members of related genera in Thermoactinomycetaceae fam. nov. The name proposed to accommodate the new isolates is Mechercharimyces gen. nov., comprising two species based on genotypic and phenotypic criteria, including comparative gyrB and DNA-DNA relatedness data. The names proposed for these taxa are Mechercharimyces mesophilus sp. nov., the type species, and Mechercharimyces asporophorigenens sp. nov., with the type strains YM3-251(T) (=MBIC06230(T)=DSM 44894(T)) and YM11-542(T) (=MBIC06487(T)=DSM 44955(T)), respectively.