Trichosporonoides nigrescens sp. nov., a new xerophilic yeast-like fungus.

A new yeast-like fungus isolated from jam on two occasions is described as Trichosporonoides nigrescens. It is a true xerophile, able to grow at water activities at least as low as 0.75. For this reason, its carbon assimilation pattern was examined using both dilute (standard) and concentrated carbon sources: six to nine compounds not assimilated at the standard concentrations of 0.5% (0.001 to 0.1 mol/kg) were assimilated at 1.5 to 2.0 mol/kg. Cell wall and septal ultrastructure, DNA base ratios, and the nuclear cycle were examined to determine the generic and higher taxonomic affinities of this microorganism. All properties were consistent with its assignment to Trichosporonoides Haskins et Spencer. However, while ultrastructure indicated an affinity with the Basidiomycetes, the mitotic nuclear cycle and the xerophilic nature of this fungus suggested an Ascomycete affinity. The GC content (57%) is consistent with assignment to either. No teleomorphic state was found.