- Volume 48, Issue 4, 1998

Nine strains were studied of a new haploid species of the genus Debaryomyces Lodder & Kreger-van Rij that had been isolated from exudates of mesquite (Prosopis juliflora) trees in southern Arizona and from Drosophila carboneria that breeds in these exudates. Their physiological characteristics, life cycle, and nuclear DNA base composition (approx. 37·5 mol% G+C) led to their original classification as Debaryomyces hansenii (Zopf) Kreger-van Rij. However, the two taxa are, at most, distantly related based on DNA reassociation values that indicated low base sequence complementarity. The two taxa also have distinctly different electrophoretic karyotypes. Debaryomyces hansenii has two varieties, D. hansenii var. hansenii and D. hansenii var. fabryi. Debaryomyces prosopidis can be differentiated phenotypically from both varieties by lack of growth on cellobiose after 2 weeks incubation and from the variety hansenii by a higher maximum temperature for growth. The type strain of Debaryomyces prosopidis sp. nov. is strain UCD-FST 84-100T (= DBVPG 7010T = CBS 8450T = ATCC 201611T).

A yeast strain isolated from the air in Japan was found to represent a new species, and was named Trichosporon japonicum. This species produced arthroconidia and appressoria. T. japonicum formed a cluster with the appressorium-forming species Trichosporon inkin and Trichosporon ovoides in a phylogenetic tree constructed using small-subunit rDNA sequences. However, they had low relatedness to each other in DNA–DNA hybridization experiments. T. japonicum is distinguished from both T. inkin and T. ovoides by its ability to assimilate inulin, and its inability to assimilate L-rhamnose. JCM 8357T is the type strain of the species.

Five new yeast species, Wickerhamiella australiensis, Wickerhamiella cacticola, Wickerhamiella occidentalis, Candida drosophilae and Candida lipophila, are described to accommodate isolates recovered from flowers and floricolous insects of Australian Hibiscus trees, cosmopolitan morning glories (Ipomoea spp.) and Brazilian cereoid cacti. The new Wickerhamiella species are heterothallic, occur in the haploid condition and are clearly separated reproductively from one another. Although they exhibit little physiological variation, they are easily delineated from Wickerhamiella domercqiae, the only species known previously, by their resistance to cycloheximide and the production of strong extracellular lipases. C. drosophilae and C. lipophila share the latter property, but unlike the Wickerhamiella species, they fail to utilize nitrate as sole nitrogen source. PFGE indicates that these yeasts have an unusually low number of chromosomes. The large-subunit rDNA (D1/D2) sequences demonstrate a close relationship between the five species and Candida vanderwaltii and Candida azyma. Their relationship with W. domercqiae is more distant, but all share, with some other Candida species, a single monophyletic clade. The type and isotype strains are as follows: W. australiensis strains UWO(PS)95–604.3T(h+; CBS 8456T) and UWO(PS)95–631.31(h+; CBS 84571); W. cacticola strains UFMG96–267T(h+; CBS 84540 and UFMG96–3811(h-; CBS 84551); W. occidentalis strains UWO(PS)91–698.4T(h+; CBS 8452T) and UFMG96–2121 (h-; CBS 84531); C. drosophilae UWO(PS)91–716.3T(CBS 8459T); and C. lipophila UWO(PS)91–681.3T(CBS 8458T).

Some Candida species which were si to each other in phenotypic characteristics were studied by chemotraxonomic and molecular taxonomic comparison including the ubiquinone systems, electrophoretic karyotypes, DNA base composition and DNA relatedness. Candida viswanathii and Candida lodderae showed similar electrophoretic karyotypes and DNA base composition and demonstrated 89 to 90 % DNA relatedness, confirming their synonymy.