Assessment of phenotypic and genetic diversity in the yeast genusMetschnikowia

The taxonomy of the yeast genusMetschnikowia has undergone profound changes over the past century. Major developments, from the capacity to obtain pure cultures of parasitic species to progress associated with the extensive use of molecular biology tools in yeast systematics, are briefly reviewed. Results from past work and new data are combined to evaluate evolutionary relationships and clarify the classification of both terrestrial and aquatic species. Recent physiological studies, including the utilization of non-conventional carbon and nitrogen sources, and characteristics like lipolytic activity and maximum temperatures for growth, are presented. The assessment of the genetic diversity within the genus by restriction analysis of the mitochondrial DNA and by the production of specific DNA probes has been explored. The results indicate the potential application of the latter in rapid identification procedures.     

Fellomyces horovitziae sp. nov., a new basidiomycetous yeast species isolated from aXenasmatella basidiocarp

A new species of the genusFellomyces, F. horovitziae, was isolated from aXenasmatella basidiocarp. It differs from other accepted species in its carbon assimilation pattern, mol% G+C and low DNA-DNA homology. The delimiting characters are discussed and a key to the genus is provided.     

Zygozyma suomiensis,sp. nov. (Lipomycetaceae), a new species from Finland

A new species of the genus Zygozyma, Z. suomiensis, is described, based on the study of a single strain, derived from a bovine skin lesion.     

PCR-ribotyping of type isolates of currently acceptedExophiala andPhaeococcomyces species

Portion of the ribosomal repeat of the type strains of the generaExphiala andPhaeococcomyces were subjected to RFLP analysis. The amplicon length of the small subunit rRNA, the fragment NS1-NS24, was found to vary between 1800 to 3200 nucleotides. In contrast, the length of the fragment ITS1-ITS4 comprising the internal transcribed spacers (ITS1 and ITS2) was found to be constant at 600 nucleotides. Analysis of restriction profiles confirmed the synonymy ofExophiala dermatitidis andMycotorula schawii. Torula bergeri andSporotrichum gougerotii were found to be identical toPhaeoannellomyces elegans, but different from their alleged synomymE. castellanii. A phenogram is presented.     

Distinction of species in Aureobasidium and related genera by PCR-ribotyping

Taxonomic markers for differentiation of the anamorph genera Aureobasidium, Hormonema and Kabatiella were developed using PCR-ribotyping with the primers 5.8S-R and LR7 for amplification and the restriction enzymes Alul, DdeI, Hhal, MspI and RsaI for digestion. Aureobasidium and Hormonema are optimally differentiated with MspI; DdeI is particularly useful to distinguish aureobasidium, Kabatiella and Selenophoma. Relationships of the anamorph genera Aureobasidium, Hormoneng and Kabatiella with the teleomorph genera Pringsheimia and Dothiora are discussed.     

Synonymy of the yeast generaWingea andDebaryomyces

Extent of divergence in partial nucleotide sequences from large and small subunit ribosomal RNAs was used to estimate the evolutionary relationship between the generaWingea andDebaryomyces. These data showed the monotypic genusWingea to be congeneric withDebaryomyces, and it is proposed to transferW. robertsii toDebaryomyces.     

Coenzyme Q systems in ascomycetous black yeasts

72 Strains belonging to 44 species of ascomycetous black yeasts were analyzed for their coenzyme Q systems. Prevalent were Q-10 and dihydrogenated Q-10 systems. Members of the Dothidealean suborder Dothideineae have Q-10 (H₂), while those belonging to the suborder Pseudosphaeriineae mostly have Q-10. The anamorph genus Exophiala Carmichael and the teleomorph genus Capronia Sacc. seem to be heterogenous.     

Population biology ofHortaea werneckii based on restriction patterns of mitochondrial DNA

Fifteen isolates ofHortaea werneckii, causative agent of tinea nigra in man, were examined with respect to restriction fragment length polymorphisms of mitochondrial DNA. Seven types of mtDNA, interpreted as populations, could be distinguished, with similarities between the restriction patterns ranging from 32 to 79%. Much of the variance originated from length mutations. Of the seven populations four represented isolates from man, two of which also comprised isolates from other sources. This makes adaptation ofH. werneckii towards association with man in its evolution unlikely; similarity in the chemical and/or physical characteristics of the different isolation sources, viz. salinity, seems more probable. mtDNA types were not correlated with geographic origin. Isolates with the same mtDNA type are widely geographically distributed.     

A study of yeasts during the delignification and fungal transformation of wood into cattle feed in Chilean rain forest

In Chilean rain forest the presence and distribution of yeasts were studied during the fungal transformation of wood, producing a partially delignified material used as cattle feed (huempe). A total of 68 yeast species was reported, including a noticeable proportions of basidiomycetous and xylose-assimilating strains, the latter related to the increased availability of this sugar in the decayed wood. The results of the mathematic comparison of taxonomic data of 327 strains showed a delimitation of sharp clusters corresponding to different species, including several new species described from this substrate, and genera, as Rhodotorula and Cryptococcus.At the initial stages of wood decay, characterized by the presence of Candida species, yeast diversity was low. The highest values were found in the medium stage of decay, used as feed, with an important presence of the genera Apiotrichum, Rhodotorula, Cryptococcus and Schizoblastosporion. After establishing a non-linear ordination from Euclidean distances between samples, based on yeast abundances, a relationship was observed between the populations developing at the different stages of wood decay by Ganoderma applanatum. A succession of yeast species was demonstrated during wood degradation by this white-rot fungus.     

Cryptococcus yarrowii sp. nov., a novel yeast species from Portugal

A novel species of the basidiomycetous genusCryptococcus is described asCr. yarrowii based on the study of an isolate from a decayed mushroom collected in Portugal. DNA-DNA homology with the type strain of the phenotypically similar speciesCr. albidus was 10±2%.