Polyphasic re-examination of Debaryomyces hansenii strains and reinstatement of D. hansenii, D. fabryi and D. subglobosus.

The type species of the genus Debaryomyces, Debaryomyces hansenii, is a highly heterogeneous species. It has been isolated from a large diversity of natural sources including fruit, air, water, soil, but most frequently from processed food products. The species delineation of this yeast species urgently needs clarification. The heterogeneity in taxonomic characteristics has resulted in the description of varieties linked to D. hansenii. The aim of this study was to re-examine and classify D. hansenii using a polyphasic approach. A total of 65 D.hansenii isolates were examined, 57 representing the variety hansenii and nine the variety fabryi. The selection of strains for DNA reassociation and phylogenetic analysis was based on polymerase chain reaction mediated fingerprints using four mini- and microsatellite-specific primers. The discriminating power of growth at 35 degrees C and 37 degrees C was re-examined and ascospore production was observed. DNA reassociations and phylogenetic analyses were performed on selected isolates from each of the clusters obtained from the DNA fingerprint analyses. The data indicated the presence of three distinct species within the D. hansenii group, which were represented by type strains of former species and that are proposed to be reinstated: D. hansenii (CBS 767(T) = MUCL 49680(T)), D. fabryi (CBS 789(T) = MUCL 49731(T)) and D. subglobosus (CBS 792(T) = MUCL 49732(T)).

Polyphasic re-examination of Yarrowia lipolytica strains and the description of three novel Candida species: Candida oslonensis sp. nov., Candida alimentaria sp. nov. and Candida hollandica sp. nov.

The type strain of Yarrowia lipolytica and 38 strains identified as Yarrowia lipolytica, four strains of Candida deformans, including the type and two subcultures of the type, two strains of Candida galli and six unidentified strains that resembled Y. lipolytica were examined by PCR fingerprints using primers M13 and (GAC)5. The same strains, together with four strains of the recently introduced Candida yakushimensis nom. inval., were sequenced for the D1/D2 domain of the 26S rRNA gene and parts of the ITS domain and also studied for their physiological properties. Of the strains identified previously as Y. lipolytica, CBS 2076 had the same fingerprint as the type of C. deformans and strain CBS 4855 was distinct from all other strains. The six strains that resembled Y. lipolytica were separated into two groups distinct from any of the other clades. A total of six groups obtained by fingerprint and sequence data were evaluated by performing DNA reassociation reactions. Mating experiments among the 35 strains of Y. lipolytica sensu stricto showed that 15 strains represented one mating type and 16 strains represented the opposite mating type, while four strains were self-sporulating. Teleomorph states were not produced by C. deformans, C. galli or any of the unidentified isolates. However, positive mating reactions were rarely observed in crosses among C. galli and some strains of Y. lipolytica and C. deformans. Consequently, sharing the same mating type system, C. deformans and C. galli could be considered anamorphs of unnamed Yarrowia species. Results from PCR fingerprints, sequencing and mating studies support the grouping of the studied strains into Y. lipolytica, C. galli, C. deformans, C. yakushimensis nom. inval. and three novel species in the Yarrowia clade: Candida oslonensis sp. nov. (type strain CBS 10146(T) =NRRL Y-48252(T); Mycobank number MB 510769), Candida alimentaria sp. nov. (type strain CBS 10151(T) =NRRL Y-48253(T); Mycobank number MB 510770) and Candida hollandica sp. nov. (type strain CBS 4855(T) =NRRL Y-48254(T); Mycobank number MB 510771).

Taxonomy and phylogeny of the ascomycetous yeast genus Zygoascus, with proposal of Zygoascus meyerae sp. nov. and related anamorphic varieties.

Physiological characters, mating compatibility, PCR-RAPD fingerprints, mol% G + C content, DNA-DNA relatedness, and large-subunit and internal transcribed spacer rRNA gene sequences of strains assigned to the genus Zygoascus were re-examined. On the basis of those data, and after phylogenetic analyses, an emendation of Zygoascus hellenicus (type material is a cross of CBS 6736(T) x CBS 5839(T)) is proposed, comprising two novel anamorphic varieties, Candida steatolytica var. steatolytica (CBS 6736(T)) and C. steatolytica var. inositophila (CBS 5839(T)). A novel teleomorphic species, Zygoascus meyerae sp. nov. (type material is a cross of CBS 4099(T) x CBS 7521(T)) is described, together with two novel anamorphic varieties corresponding to it, Candida hellenica var. hellenica (CBS 4099(T)) and C. hellenica var. acidophila (CBS 7115(T)).

Recurrent isolation of an uncommon yeast, Candida pararugosa, from a sarcoma patient.

A yeast was repeatedly isolated from the saliva of a sarcoma patient. A relatively uncommon species, Candida maris, was identified based on the API 20C profile. The yeast species most frequently obtained from the patient's mother and from clinic staff was Candida albicans. A comparison of the yeast obtained from the patient with the type strain of C. maris strongly suggested that the former was not representative of C. maris. Analysis of partial ribosomal DNA sequences of the patient strain and from the type strain of C. maris showed that the two are phylogenetically not closely related. The patient strain was very close to Candida pararugosa, a relatively uncommon asporogenous yeast. DNA reassociation studies among C. pararugosa and patient isolates showed that they were conspecific. We could not determine the source of the yeast infection. This case will alert hospital staff to be aware of the possibility of unexpected environmental microorganisms as causes of infections, colonizations and persistent environmental contamination events in immunocompromised patients.

Genome comparisons in the genus Dipodascus de Lagerheim.

Phenotypic characteristics of physiology and morphology of 71 strains belonging to the genus Dipodascus de Lagerheim were examined. The GC contents of genomic DNAs of 46 strains were calculated from the thermal denaturation curves using the spectrophotometric method. The first derivatives of the melting curves revealed that the DNAs of these strains are heterogeneous; four categories could be recognized. However, DNA similarity values calculated by using DNA-DNA reassociation kinetics showed that each category could be subdivided further. Two categories were separated into four subgroups each; the other two yielded five subgroups each. Strains belonging to the same subgroup exhibited high levels of DNA similarity ranging from 82 to 100%. The 18 subgroups represented 13 currently accepted Dipodascus species and five anamorphic Geotrichum species, four representing novel taxa. A phenotypic key to distinguish the taxa of Dipodascus, Galactomyces and Geotrichum is presented.

Ascobotryozyma americana gen. nov. et sp. nov. and its anamorph Botryozyma americana, an unusual yeast from the surface of nematodes.

A new teleomorphic genus Ascohotryozyma, with a single species, A. americana, is proposed. Its anamorph is a Botryozyma that differs from the type species, B. nematodophila, on distributional, physiological, and molecular criteria; it is described as Botryozyma americana, anam. sp. nov. Ascobotryozyma is characterized by globose asci bearing four lunate ascospores. Fusion of thallus cells precedes ascus formation. Ascobotryozyma americana was isolated from the surface of nematodes (Panagrellus dubius) associated with galleries of the poplar borer (Saperda calcarata) in trembling aspen (Populus tremuloides) in eastern Washington, USA. The teleomorph has not been produced in pure culture.

Re-examination of some species of the genus Geotrichum Link: Fr.

The nutritional physiology and the growth rate of thirty-four strains representing species of Geotrichum without known teleomorph states were examined. From twenty-seven strains the mol% G+C were calculated from the DNA melting curves. The first derivatives of the melting curves of seven strains, including the type strain of Geotrichum clavatum, demonstrated the presence of two peaks, 12% away from each other; the remaining strains showed only a single broad peak. DNA homology values among strains of the former group were high, indicating their conspecificity. The strains of the latter group could be subdivided into six DNA homology groups, four of which could be identified with recognized species and two may represent novel taxa. A combined key of Geotrichum and its teleomorph states Galactomyces and Dipodascus is presented.

Dipodascus capitatus, Dipodascus spicifer and Geotrichum clavatum: genomic characterization.

The G + C contents of 25 strains of Dipodascus capitatus, Dipodascus spicifer and Geotrichum clavatum were found to be heterogeneous on basis of derivative graphs of the melting profiles. Strains showing similar derivative graphs of the melting curve exhibited high levels of DNA homology (80-100%); strains showing dissimilar derivative graphs exhibited low levels of DNA homology (5 to 45%). Being considered separate taxa on basis of these parameters, D. capitatus, D. spicifer and G. clavatum could be identified by a combination of the key characteristics growth on xylose, cellobiose, salicin and arbutin.

Genome comparisons in the yeastlike fungal genus Galactomyces Redhead et Malloch.

The G+C contents of the DNAs of 41 strains belonging to the genus Galactomyces Redhead et Malloch were determined by the thermal denaturation method. Melting profiles revealed that the DNAs of these strains are heterogeneous. Four groups were recognized on the basis of this heterogeneity. However, DNA similarity values, which were calculated by using DNA-DNA reassociation kinetics, revealed that the strains could be divided into six subgroups. Strains belonging to the same subgroup exhibited high levels of DNA similarity (84 to 100%). The members of two subgroups, corresponding to Galactomyces citri-aurantii and Galactomyces reessii, exhibited low levels of DNA similarity with the members of the other subgroups (20 to 27%). The members of the four remaining subgroups, which contained only strains previously identified as Galactomyces geotrichum, exhibited intermediate levels of reassociation (41 to 59%). Some combinations of phenotypic characteristics correlated with the subgroups; a key based on phenotypic characteristics that can be used to distinguish the subgroups is presented.

Species delimitation in the genus Lipomyces by nuclear genome comparison.

Species delimitation in Lipomyces was attempted by nuclear genome comparison in conjunction with the re-evaluation of 48 physiological characters of 65 strains. High intraspecific (> 75%) and low interspecific (< 28%) similarity values established that L. japonicus, L. lipofer and L. tetrasporus are genetically isolated, and also distinct from L. kononenkoae and L. starkeyi. Ambiguous similarity values were obtained with L. kononenkoae and L. starkeyi. Strains previously assigned to L. kononenkoae constitute two related clusters. While similarity values within each cluster range from 76-99%, representatives of the two clusters reassociate for only 47%. Since these clusters are differentiated by their ecologically relevant maximum growth temperature, L. kononenkoae is subdivided. Strains previously assigned to L. starkeyi resolve into four closely related clusters. While similarity values within each cluster range from 78-100%, representatives of the four clusters reassociate for only 59-69%. Since these four clusters are poorly differentiated, the subdivision of L. starkeyi does not appear possible without recourse to other criteria. Four unassigned strains constitute a further two clusters. Reassociation within these clusters is of the order of 91-100%, while reassociation between them occurs only at 59%. Reassociation of representatives of these clusters with those of the L. kononenkoae and L. starkeyi complexes is around 40% and 31%, respectively. These two clusters consequently appear to be intermediate between L. kononenkoae and L. starkeyi, and will, as such, have to be considered in any delimitation of these two species. A key to the taxa of Lipomyces and related genera of the Lipomycetaceae is given.

Genome comparison among species of the genus Arthroascus von Arx.

Genome comparison in strains of the genus Arthroascus indicates that two species, A. javanensis (CBS 2555, Type) and A. schoenii (CBS 7223, Type), can be recognized.

Dekkera, Brettanomyces and Eeniella: electrophoretic comparison of enzymes and DNA-DNA homology.

The taxonomic status of various species of Dekkera, Brettanomyces and Eeniella was examined by electrophoretic comparison of enzymes, by deoxyribonucleic acid homology and by physiological characterization. These studies demonstrated that two teleomorphic Dekkera species, D. anomala and D. bruxellensis (synonym D. intermedia), and four anamorphic Brettanomyces species, B. anomalus (synonym B. claussenii), B. bruxellensis (synonym B. abstinens, B. custersii, B. intermedius, B. lambicus), B. custersianus and B. naardenensis, can be recognized. The anamorphic genus Eeniella remained as a separate, monotypic taxon.

Species delineation in the genus Nadsonia Sydow.

The genus Nadsonia Sydow is revised on the basis of morphology, physiology, amino acid and fatty acid composition, electrophoretic patterns of some enzymes and DNA relatedness. Two species, N. commutata (type CBS 6640) and N. fulvescens, with two varieties, N. fulvescens var. fulvescens (type CBS 2596) and N. fulvescens var. elongata (type CBS 2594) nov. comb. are recognized. A modified diagnosis of the genus and a key are given.

Conspecificity of Hanseniaspora nodinigri and Hanseniaspora vineae: comparison by DNA reassociation.

Hanseniaspora nodinigri Lachance 1981, found in black knots (caused by Dibotryon morbosum) of Prunus virginiana, was described as a new species, some time after publication of the extensive study by Meyer et al. (1978) on the systematics of Hanseniaspora Zikes and its imperfect counterpart Kloeckera Janke. Lachance delimited the species from other members of the genus because of absence of growth on glucono-delta-lactone. He also stated that this species, although evidently similar in many ways to H. vineae van der Walt et Tscheuschner and H. osmophila (Niehaus) Phaff et al., has 'diverged from them, possibly in its adaptation to growth in association with black knots'.