Six new anamorphic ascomycetous yeasts near Candida tanzawaensis

Six new species of the yeast genus Candida are described from their unique nucleotide sequences in the D1/D2 domain of 26S rDNA. Five of these species form a clade with Candida tanzawaensis, and the sixth is basal to this group. The new species and their sources of isolation are the following: Candida ambrosiae (type strain NRRL YB-1316, CBS 8844), from insect frass, rotted wood and mushroom fruiting bodies; Candida canberraensis (type strain NRRL YB-2417, CBS 8846), from soil; Candida caryicola (type strain NRRL YB-1499, CBS 8847), from a pignut hickory tree; Candida prunicola (type strain NRRL YB-869, CBS 8848), from exuded gum of a black cherry tree; Candida pyralidae (type strain NRRL Y-27085, CBS 5035), from insect frass; Candida xylopsoci (type strain NRRL Y-27066, CBS 6037), from insect frass.     

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.     

Electron microscopy of septa in ascomycetous yeasts

Electron micrographs of septa in ascomycetous, filamentous yeasts showed three types of structure, namely, dolipores, plasmodesmata, and a central connection indicated as a closure line. The taxonomic use of these and some other morphological features is surveyed.     

Systematics of the ascomycetous yeasts assessed from ribosomal RNA sequence divergence

Extent of divergence in partial nucleotide sequences from large and small subunit ribosomal RNAs was used to estimate genetic relationships among ascomycetous yeasts and yeastlike fungi. The comparisons showed four phylogenetically distinct groups comprised of the following taxa: Group 1. The budding yeastsSaccharomyces, Saccharomycopsis, Debaryomyces, Metschnikowia, Saturnospora, andLipomyces, and the yeastlike generaAscoidea, Cephaloascus, Dipodascus, Dipodascopsis, andGalactomyces; Group 2.Eremascus, Emericella andCeratocystis; Group 3.Taphrina andProtomyces; Group 4.Schizosaccharomyces. Because of the genetic relationships indicated by sequence analysis, Group 1 taxa are retained in the order Endomycetales, andSchizosaccharomyces is retained in the Schizosaccharomycetales Prillinger et al. ex Kurtzman.     

Killer-sensitive relationships in yeasts from natural habitats

Yeast strains (157) belonging to at least 9 genera were isolated from natural habitats and screened for killer-sensitive relationships. Killer and sensitive characteristics were exhibited by 17 and 11 percent of the isolates, respectively. The strains belong to either one of two mutually exclusive killer-sensitive groups.     

Relation between phylogeny and physiology in some ascomycetous yeasts

The question of whether yeasts with similar physiological properties are closely related has been examined using recently published phylogenetic analyses of 26S domain D1/D2 rDNA nucleotide sequences from all currently recognized ascomycetous yeasts. When apparently unique metabolic pathways are examined, some relationships between physiology and rDNA phylogeny are evident. Most Candida and Pichia species that are able to assimilate methanol as the sole carbon source are in a clade delimited by C. nanospora and C. boidinii. Exceptions are P. capsulata and P. pastoris which are phylogenetically separated from the other methanol-assimilating yeasts. Yeasts subject to the petite mutation, resulting in respiratory deficiency, belong to three different clades, viz. a Saccharomyces clade delimited by S. cerevisiae and S. rosinii,the Dekkera/Brettanomyces clade, and some Schizosaccharomyces species (‘Archiascomycete’ clade). However, petite mutants were also found in Zygosaccharomyces fermentati and some other more distantly related species. Yeasts able to assimilate n-hexadecane, uric acid or amines as sole carbon source are broadly distributed over the ascomycetous phylogenetic tree. However, species that assimilate adenine as sole carbon source are closely related. Most of these species also assimilated glycine, uric acid, n-hexadecane, putrescine and branched-chain aliphatic compounds such as isobutanol, leucine and isoleucine. Among the Saccharomycetales, species utilizing all or the great majority of these eight compounds are in the Stephanoascus/Arxula/Blastobotrys clade. Candida blankii, which is distantly related to this clade, proved to be an exception and assimilated six of eight of these compounds. This revised version was published online in June 2006 with corrections to the Cover Date.     

Hexose and pentose transport in ascomycetous yeasts: an overview

The biochemical characterization of sugar uptake in yeasts started five decades ago and led to the early production of abundant kinetic and mechanistic data. However, the first accurate overview of the underlying sugar transporter genes was obtained relatively late, due mainly to the genetic complexity of hexose uptake in the model yeast Saccharomyces cerevisiae . The genomic era generated in turn a massive amount of information, allowing the identification of a multitude of putative sugar transporter and sensor-encoding genes in yeast genomes, many of which are phylogenetically related. This review aims to briefly summarize our current knowledge on the biochemical and molecular features of the transporters of hexoses and pentoses in yeasts, when possible establishing links between previous kinetic studies and genomic data currently available. Emphasis is given to recent developments concerning the identification of d -xylose and l -arabinose transporter genes, which are thought to be key players in the optimization of S. cerevisiae strains for bioethanol production from lignocellulose hydrolysates.     

Control of mites during isolation of yeasts from natural habitats

Summary Addition of 6.6 ml /liter of cygon (dimethoate, commercial) to acidified malt extract agar (Difco YM medium) suppressed mite activity completely and did not appear to affect the number or species of yeasts isolated. Rose Bengal suppressed filamentous fungi to some extent.     

A colour reaction for the differentiation of ascomycetous and hemibasidiomycetous yeasts

Seventy yeast strains, representative of twenty-six ascogenous genera, four saprobic hemibasidiomycetous genera and thirteen genera of the Cryptococcales were tested for their reaction with the stabilized aromatic diazonium compound, Diazonium Blue B salt. An aqueous, buffered solution of this compound gave a characteristic red colouration with the colonies of the hemibasidiomycetous species and those Cryptococcales characterized by the hemibasidiomycetous cell-wall type. The characteristic colour reaction was not observed with colonies of either the ascomycetous yeasts or those Cryptococcales characterized by the ascomycetous cell-wall type.The possible taxonomic use of the colour reaction with Diazonium Blue B salt as an affinitive characteristic is discussed.     

Temperature optima for bacteria and yeasts from cold-mountain habitats.

Optimal temperatures for the growth of bacteria and yeasts isolated from several cold-mountain habitats were determined. The lowest optimal temperatures encountered were in the 10-15 degrees C range, even though most of the isolates were obtained from sites at or near 0 degrees C.