Phylogenetic relationships among species of the genus Issatchenkia Kudriavzev

The phylogenetic relatedness of Issatchenkia spp. was estimated from partial rRNA sequences in two regions of the large subunit and one region of the small subunit. I. terricola was the most divergent species of the genus, differing from other members by 18% nucleotide differences in the highly variable 25S-635 region. These data indicate Issatchenkia to be the most divergent ascomycetous yeast genus presently known.     

Heterothallism in Pichia kudriavzevii and Pichia terricola

Pichia kudriavzevii and P. terricola were found to be heterothallic, but not interfertile with one another; nor did they mate with P. membranaefaciens, P. scutulata, Candida lambica, C. diversa, C. ingens, C. silvae, C. valida, C. vini, C. norvegensis, or Torulopsis inconspicua. Limited conjugation occurred between mating types of P. kudriavzevii and C. krusei and conjugation and sporulation occurred in mixtures with C. sorbosa. The data indicate C. krusei and C. sorbosa to be the same species and to represent imperfect forms of P. kudriavzevii.     

Yeast species recognition from gene sequence analyses and other molecular methods

This review discusses DNA-based methods used for identification of yeasts. Nuclear DNA reassociation was the first quantitative molecular method employed for recognition of yeast species and has provided a baseline for interpretation of other molecular comparisons. Among these, gene sequencing is the most definitive method, with ribosomal RNA gene sequences providing the preponderance of available data. Multigene analyses that include the sequences of protein encoding genes are being increasingly developed to provide a more definitive resolution of species. A number of rapid identification methods, such as denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE), and flow cytometry, which are based on species-specific gene sequences, are available for use in diagnostic laboratories.     

Candida arabinofermentans, a new L-arabinose fermenting yeast

Candida arabinofermentans (type strain NRRL YB-2248, CBS 8468), a new yeast that ferments the pentose L-arabinose, is described. The three known strains of this new species were isolated from insect frass of pine and larch trees in the U.S. Phylogenetic analysis of nucleotide sequences from the D1/D2 domain of large subunit (26S) ribosomal DNA places C. arabinofermentans among the methanol-assimilating yeasts and most closely related to Candida ovalis. Strains of the new species produce 0.7-1.9 g/l ethanol from L-arabinose.     

Identification and phylogeny of ascomycetous yeasts from analysis of nuclear large subunit (26S) ribosomal DNA partial sequences

Approximately 500 species of ascomycetous yeasts, including members of Candida and other anamorphic genera, were analyzed for extent of divergence in the variable D1/D2 domain of large subunit (26S) ribosomal DNA. Divergence in this domain is generally sufficient to resolve individual species, resulting in the prediction that 55 currently recognized taxa are synonyms of earlier described species. Phylogenetic relationships among the ascomycetous yeasts were analyzed from D1/D2 sequence divergence. For comparison, the phylogeny of selected members of the Saccharomyces clade was determined from 18S rDNA sequences. Species relationships were highly concordant between the D1/D2 and 18S trees when branches were statistically well supported.     

Penicillic Acid Production by Blue-Eye Fungi on Various Agricultural Commodities

Of 10 Penicillium species reported to cause blue-eye disease of corn, four (P. martensii, P. palitans, P. cyclopium, P. puberulum) were found capable of producing the mycotoxin penicillic acid on various agricultural commodities. Commodities with high protein contents did not support toxin synthesis. The extent of toxin production varied with the strain of mold, the commodity, and the temperature; low temperatures (1 to 10 C) favored toxin accumulation.