- Volume 42, Issue 4, 1992

Small-subunit rRNAs from 24 gram-negative methylotrophic bacteria have been sequenced. A phylogenetic tree was constructed on the basis of sequence similarities by using a weighted least-mean-square difference method. The methylotrophs were separated into coherent clusters in which bacteria in each group shared physiological characteristics.

Cryptococcus albidus, which was described as having maximum growth temperatures (Tmax) that vary from <20 to >37°C, is an apparent exception to van Uden’s rule that yeast species generally comprise strains which have Tmax that vary by not more than 5°C. This exception is dealt with in this paper by the description of phenotypically similar species that have lower Tmax than C. albidus and exhibit no significant DNA similarity to the type strain of C. albidus. Cryptococcus albidosimilis sp. nov., a mesophilic blastobasidiomycete that was isolated from soil of Linnaeus Terrace, Antarctica (type strain, strain MYSW A823-2Y761/70 [= ATCC 76863, = CBS 7711, = NRRL Y-17463]), has a Tmax of 30°C and a guanine-plus-cytosine content of 55 mol%. Cryptococcus antarcticus sp. nov. is a psychrophilic blastobasidiomycete (type strain, strain MYSW A812-20bY693/64 [= ATCC 76663, = CBS 7687, = NRRL Y-17461]) is known only from soils of University Valley, Antarctica. C. antarcticus does not exhibit significant DNA similarity with C. albidosimilis, from which it differs phenotypically in its failure to assimilate lactose. The guanine-plus-cytosine content of C. antarcticus is 55 mol%. This species includes four biotypes whose levels of DNA similarity are greater than 72%. The Tmax of these biotypes vary from >15 and <20°C to >20 and <25°C. Both habitat temperature (reflected in fatty acid composition) and the sporadic availability of liquid water in University Valley apparently were factors in the evolution of this species.

The Judicial Commission designated strain MF (DSM 1535) as the type strain of Methanobacterium formicicum. At the same time, it designated strain M.o.H. (DSM 863) as the type strain of Methanobacterium bryantii.