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PubMed1987

An endogenous inducer of sexual development in Aspergillus nidulans.

During development of the homothallic ascomycete Aspergillus nidulans, asexual sporulation is followed by sexual sporulation. We report here the detection of a solvent-extractable activity which inhibits asexual sporulation and stimulates premature sexual sporulation. This activity, called precocious sexual inducer (psi), is overproduced by certain mutants that are blocked in both modes of sporulation. Using partially purified preparations of psi, biological response could be elicited with as little as 50 ng of material. We suggest that psi is a hormone-precursor which is converted to a hormone by normal sporulating strains that respond to psi, but not by the asporogenous mutants that overproduce psi. The stability of psi activity gives promise that the compound can be purified and identified.

Aspergillus nidulans↗
PubMed1990

Numerical taxonomic analysis of imperfect yeast species in Candida and Torulopsis shows no basis for generic separation.

A numerical taxonomic analysis was performed on 79 phenotypic characters of 147 imperfect yeast species currently assigned to the genus Candida. The characters used were drawn from two monographs on yeast taxonomy. The analysis revealed 10 clusters of three or more species that were similar at the level of 75% or more, and seven clusters containing only one or two species. None of the 10 major clusters contained exclusively species that were traditionally assigned to the genus Torulopsis, while the 12 Candida species of basidiomycetous affinity fell into three clusters with only one species of ascomycetous affinity included. Statistical determination of the five most important differential characters for each cluster failed to show the property of pseudomycelium/mycelium formation as significant for any cluster. The study provides no evidence to support a distinction between taxa that were formerly divided between the genera Candida and Torulopsis and supports previous proposals that these genera should be fused.

Candida↗
PubMed1990

The cellulase complex of Neurospora crassa: activity, stability and release.

The temperature and pH optima, and the temperature and pH stability, of crude and purified enzymes of the cellulase complex of the cellulolytic ascomycete fungus Neurospora crassa were investigated. The effects of some non-ionic surfactants and fatty acids on the production/release of enzymes of cellulase complex were also examined. For the different enzymes of the complex, activity maxima occurred between pH 4.0 and 7.0, with pH 5.0 being close to optimal for stability of all. Temperature optima for activity ranged between 45 and 65 degrees C, with the stability optimum between 45 and 50 degrees C. The presence of C18 fatty acids and surfactants resulted in increased production of both endoglucanase and exoglucanase in the medium. Oleic acid was the most effective fatty acid tested, and Tween 80 the most effective surfactant. Oleic acid had no detectable effect on production of beta-glucosidase, and Tween 80 actually reduced its production.

Cellulase↗
PubMed1992

Small subunit ribosomal RNA of Blastomyces dermatitidis: sequence and phylogenetic analysis.

We determined the small subunit (18S) ribosomal RNA sequence of the dimorphic fungus Blastomyces dermatitidis. The sequence was compared to that of fourteen other eukaryotic organisms, ten of which were higher fungi, and an evolutionary tree was constructed based on these sequences. B. dermatitidis aligned most closely with the Ascomycetes Neurospora crassa and Podospora anserina, in agreement with previous phylogenetic analysis based on morphological criteria. Phase-specific cDNA clones derived by reverse transcription of RNA isolated from the yeast and mycelial phases of B. dermatitidis were also sequenced. The 18S ribosome sequence was found to be the same in both phases. Heterogeneity was found at both the genomic and RNA level at position 1352.

Base Sequence↗
PubMed1994

Evidence for a phylogenetic connection between Coccidioides immitis and Uncinocarpus reesii (Onygenaceae).

Coccidioides immitis is an anomaly amongst the human systemic fungal pathogens. Its unique parasitic cycle has contributed to confusion over its taxonomy. Early investigators mistakenly suggested that the pathogen is a protist, while others agreed it to be a fungus but placed it in four different divisions of the Eumycota. The taxonomy of C. immitis is still unresolved. Ultrastructural examinations of its parasitic and saprobic phases have revealed features that are diagnostic of the ascomycetous fungi. Moreover, striking similarities between the kind of asexual reproduction (i.e. arthroconidium formation) of this pathogen and certain anamorphic and teleomorphic members of the genus Malbranchea have suggested a close relationship. Teleomorphs of these Malbranchea species are members of the Onygenaceae (Order, Onygenales). This family also includes teleomorphs of two human respiratory pathogens, Histoplasma capsulatum and Blastomyces dermatitidis. Although the 18S rRNA gene sequences (1713 bp) of these two pathogenic forms differ from that of C. immitis by only 35 and 33 substitutions, respectively, their mode of conidiogenesis is characterized by production of solitary aleurioconidia rather than alternate arthroconidia. In this study we have used characters derived from biochemical, immunological and molecular analyses to compare relatedness between C. immitis, H. capsulatum, B. dermatitidis, and six non-pathogenic species of Malbranchea (the Malbranchea states of Uncinocarpus reesii and Auxarthron zuffianum, as well as M. albolutea, M. dendritica, M. filamentosa and M. gypsea). Evidence is presented which supports inclusion of C. immitis in the Onygenaceae, and indicates that a close phylogenetic relationship exists between the Malbranchea state of U. reesii and this respiratory pathogen.

Amino Acid Sequence↗
PubMed1997

Glyceraldehyde-3-phosphate dehydrogenase expression in Trichoderma harzianum is repressed during conidiation and mycoparasitism.

A glyceraldehyde-3-phosphate dehydrogenase (gpd) cDNA was isolated from the filamentous fungus Trichoderma harzianum in the course of a search for light-regulated genes in this organism. There is apparently only one copy of gpd in the T. harzianum genome, and its sequence is most similar to that of other filamentous ascomycetes. Trichoderma grows in the soil as a saprophyte or mycoparasite. A brief pulse of blue light, or nutrient depletion, induces sporulation, which is accompanied by altered patterns of abundance of specific polypeptides. Mycoparasitic development is also accompanied by changes in gene expression. The abundance of gpd mRNA decreased strongly during sporulation, and was lowest in samples consisting o mature conidiophores and conidia. When T. harzianum was grown in the presence of cell walls of the phytopathogen Rhizoctonia solani, the gpd mRNA level was much lower than in similar cultures grown on glucose. The repression of gpd, which is usually considered a constitutively expressed gene, may be part of the switch to sporulation or to the simulated mycoparasitic state. The implications of these findings for the use of gpd promoters to confer high constitutive expression are discussed.

Amino Acid Sequence↗
PubMed1997

beta-Glucosylated proteins in the cell wall of the black yeast Exophiala (Wangiella) dermatitidis.

Wild-type cells of the pathogenic black yeast Exophiala (Wangiella) dermatitidis grown in a low-pH ascorbate medium became less melanized and less resistant to Zymolyase. This was accompanied by increased staining with fluorescently labelled concanavalin A. The sugar composition of wild-type and mutant cell walls was, except for the presence of galactose, similar to that of Saccharomyces cerevisiae. Digestion of mutant cell walls with laminarinase released galactomannoproteins. In addition, the released cell wall proteins contained glucose and reacted with affinity-purified 1,6-beta-glucan antiserum, indicating that they are linked to 1,6-beta-glucan. It is proposed that 1,6-beta-glucosylated cell wall proteins generally occur among ascomycetes.

Carbohydrate Conformation↗
PubMed1999

Oocydin A, a chlorinated macrocyclic lactone with potent anti-oomycete activity from Serratia marcescens.

A unique chlorinated macrocyclic lactone, termed oocydin A, was isolated from a strain of Serratia marcescens growing as an epiphyte on Rhyncholacis pedicillata, an aquatic plant native to the Carrao river of the Venezuelan-Guyanan region of South America. The lactone has a molecular mass of 470 Da, and contains one atom of chlorine, a carboxyl group and a tetrahydrofuran ring internal to a larger macrocyclic ring. MICs of approximately 0.03 microg ml(-1) were noted for oocydin A against such phytopathogenic oomycetes as Pythium ultimum, Phytophthora parasitica, Phytophthora cinnamomi and Phytophthora citrophora. With regard to the true fungi, oocydin A had either minimal or no effect against certain Fungi Imperfecti (including several pathogens of humans), two ascomycetes and a basidiomycete. Oocydin A may have potential as an antimycotic in agricultural applications and especially for crop protection.

Antifungal Agents↗
PubMed2001

A peptidorhamnomannan from the mycelium of Pseudallescheria boydii is a potential diagnostic antigen of this emerging human pathogen.

The ascomycete Pseudallescheria boydii is an emerging human pathogen frequently found in soil and polluted water. A peptidopolysaccharide antigen has been isolated from mycelial forms of P. boydii, and characterized using chemical and immunological methods. Monosaccharide composition, methylation analysis, and (1)H- and (13)C-NMR spectra indicated the presence of a rhamnomannan with a structure distinct from those of similar components isolated from other fungi, containing Rhap(1-->3)Rhap epitopes on side chains which may be linked (1-->3) to (1-->6)-linked mannose. The peptidorhamnomannan from P. boydii reacted poorly with an antiserum raised against whole cells of Sporothrix schenckii and strongly with one against P. boydii hyphae. These characteristics and immunological differences suggest that this major rhamnose-containing antigen of P. boydii may be useful for the specific diagnosis of infections attributable to this fungus.

Animals↗
PubMed1995

Anti-Candida activity of a novel killer toxin from the yeast Williopsis mrakii.

A screening of putative killer yeast strains showed that spore-forming ascomycetous yeasts of the genera Pichia and Williopsis displayed the broadest range of activity against sensitive strains of Candida spp. and Saccharomyces cerevisiae. Williopsis mrakii (NCYC 500) showed extensive anti-Candida activity against strains isolated from clinical specimens. W. mrakii killer factor was produced in minimal media as a function of growth and its activity reached constant levels as cells entered stationary phase. The proteinaceous killer toxin was found to be unstable without a specific range of temperature and pH (above 30 degrees C and pH 4.0), and further analysis showed that the active toxin molecule was an acidic polypeptide with a relative molecular mass between 1.8-5.0 kDa. At critical concentrations the killer factor exerted a greater effect on stationary phase cells of Candida than cells from an exponential phase of growth. At low concentrations, the killer toxin produced a fungistatic effect on sensitive yeasts but at higher concentrations there was evidence to suggest that membrane damage accounted for the zymocidal effects of the killer factor. the cidal nature of the toxin was reflected in a rapid decrease in sensitive cell viability. Findings presented suggest that W. mrakii killer toxin has potential as a novel antimycotic agent in combatting medically important strains of Candida.

Antifungal Agents↗
PubMed1996

The localization of chitin synthase in membranous vesicles (chitosomes) in Neurospora crassa.

Polyclonal anti-chitin synthase antibodies raised against the Saccharomyces cerevisiae CHS2 gene product were used to identify and localize chitin synthase in the filamentous ascomycete Neurospora crassa. A single band of approximately 110 kDa was observed in Western blots of total protein extracts of N. crassa, probed with these antibodies. However, several additional bands were labelled when membrane fraction proteins (microsomes) were probed. Histo-immunochemical localization of chitin synthase confirmed that the polypeptide is compartmentalized in membranous vesicles (chitosomes), which are abundant in the vicinity of the hyphal tip. TEM analysis did not reveal chitin synthase in the plasma membrane. However, dense labelling of membrane-associated chitin synthase was observed by light-microscopic analysis of N. crassa protoplasts and at young hyphal tips.

Antibodies, Fungal↗
PubMed1996

Sequence analysis and regulation of a gene encoding a cuticle-degrading serine protease from the nematophagous fungus Arthrobotrys oligospora.

The nematode trapping fungus Arthrobotrys oligospora produces an extracellular serine protease (designated PII) that immobilizes free-living nematodes in bioassays and hydrolyses proteins of the nematode cuticle. Peptides were isolated from PII and partly sequenced. Three internal peptide sequences were used to design synthetic oligonucleotides, which allowed the subsequent isolation of the gene encoding PII from a genomic library. The deduced amino acid sequence indicated that PII is synthesized as a preproenzyme containing the mature enzyme, a signal sequence and a propeptide that are removed before the enzyme is secreted into the medium. The primary sequence of PII displayed a high degree of similarity with several other serine proteases of ascomycetes belonging to the subtilisin family. Northern analysis demonstrated that PII was expressed when the fungus was starved of nitrogen and carbon and that the expression was significantly stimulated by the addition to the medium of various soluble and insoluble proteins, including fragments of nematode cuticle. The levels of the mRNA as well as the proteolytic activity of PII were repressed in the presence of more easily metabolized forms of nitrogen (including ammonia, nitrate and amino acids) or glucose. The activity of the enzyme was almost completely inhibited by the peptide Phe-Val, as well as by the amino acid Phe, without a corresponding decrease in mRNA level. Notably, peptides with similar structures are known to be secreted by the host (nematode) and to stimulate the production of infection structures (traps) of the fungus.

Amino Acid Sequence↗
PubMed2005

Description of Komagataella phaffii sp. nov. and the transfer of Pichia pseudopastoris to the methylotrophic yeast genus Komagataella.

The new methanol-assimilating yeast species Komagataella phaffii Kurtzman sp. nov. (type strain NRRL Y-7556(T)=CBS 2612(T)) is described. Of the four known strains of this species, two were isolated from black oak trees in California, USA, one from an Emory oak in Arizona, USA, and one from an unidentified source in Mexico. The species forms hat-shaped ascospores in deliquescent asci and appears to be homothallic. Analysis of nucleotide sequences from domains D1/D2 of large-subunit (26S) rDNA separates the new species from Komagataella pastoris, the type species of the genus, and from Pichia pseudopastoris, which is here renamed Komagataella pseudopastoris (Dlauchy, Tornai-Lehoczki, Fulop & Peter) Kurtzman comb. nov. (type strain NRRL Y-27603(T)=CBS 9187(T)=NCAIM Y 01541(T)). On the basis of D1/D2 26S rDNA sequence analysis, the three species now assigned to the genus Komagataella represent a clade that is phylogenetically isolated from other ascomycetous yeast genera.

DNA, Fungal↗
PubMed2005

Candida bromeliacearum sp. nov. and Candida ubatubensis sp. nov., two yeast species isolated from the water tanks of Canistropsis seidelii (Bromeliaceae).

Strains belonging to two novel yeast species, Candida bromeliacearum and Candida ubatubensis, were isolated from the bromeliad tank of Canistropsis seidelii (Bromeliaceae) in a sandy coastal plain (restinga) ecosystem site in an Atlantic rainforest of south-eastern Brazil. These species were genetically distinct from all other currently accepted ascomycetous yeasts, based on sequence divergence in the D1/D2 domains of the large-subunit rDNA and in the small-subunit rDNA. The species occupy basal positions in the Metschnikowiaceae clade. The type strains are Candida bromeliacearum UNESP 00-103(T) (=CBS 10002(T)=NRRL Y-27811(T)) and Candida ubatubensis UNESP 01-247R(T) (=CBS 10003(T)=NRRL Y-27812(T)).

Brazil↗
PubMed2006

Candida floccosa sp. nov., a novel methanol-assimilating yeast species.

Two methanol-assimilating yeast strains were isolated from a flux of a sessile oak (Quercus petrea) in Hungary and one genetically and phenotypically very similar strain from a flux of a red oak (Quercus rubra) in Canada. The strains exhibited ascomycetous affinity but ascospore formation was not observed. On the basis of the sequence of their D1/D2 domain of the large subunit rDNA, as well as of their physiological characteristics, they represent a novel yeast species of the genus Candida. Therefore Candida floccosa sp. nov. is proposed, with NCAIM Y.01581(T) (=CBS 10307(T)=NRRL Y-27951(T)) as the type strain.

Candida↗
PubMed2003

Characterization, localization and functional analysis of Gpr1p, a protein affecting sensitivity to acetic acid in the yeast Yarrowia lipolytica.

Adaptation of cells to acetic acid requires a hitherto unknown number of proteins. Studies on the GPR1 gene and its encoded protein in the ascomycetous fungus Yarrowia lipolytica have revealed an involvement of this protein in the molecular processes of adaptation to acetic acid. Gpr1p belongs to a novel family of conserved proteins in prokaryotic and eukaryotic organisms that is characterized by the two motifs (A/G)NPAPLGL and SYG(X)FW (GPR1_FUN34_YaaH protein family). Analysis of four trans-dominant mutations and N-terminal deletion analysis of Gpr1p identified the amino acid sequence FGGTLN important for function of this protein in Y. lipolytica. Deletion of GPR1 slowed down adaptation to acetic acid, but had no effect on growth in the presence of acetic acid. Expression of GPR1 is induced by acetic acid and moderately repressed by glucose. It was shown by subcellular fractionation that Gpr1p is an integral membrane protein, which is also suggested by the presence of five to six putative transmembrane spanning regions. Fluorescence microscopy confirmed a localization to the plasma membrane. A model is presented describing a hypothetical function of Gpr1p during adaptation to acetic acid.

Acetic Acid↗
PubMed2003

Analysis of microtubules and F-actin structures in hyphae and conidia development of the opportunistic human pathogenic black yeast Aureobasidium pullulans.

Organization of the cytoskeleton was studied in the ascomycetous black yeast Aureobasidium pullulans, an opportunistic human pathogen, in an effort to present it as a potential target of antifungal therapy. Long cytoplasmic microtubules, extending along the hyphae from the base to the growing apex, were the dominant structures in multinucleate interphase cells. Before mitosis these microtubules disappeared and were replaced by intranuclear spindles. This reorganization of microtubules occurred along the whole length of hypha before synchronous division of the nuclei. Actin cytokinetic rings were rarely seen. Cortical actin in the form of patches accumulated in areas of cell wall growth, i.e. in the hyphal apex and near the occasionally formed septum. Actin cables were not seen. During synchronous conidiogenesis, the cytoplasmic microtubules extended along developing conidia, and actin patches lined their subcortical areas. Actin rings were formed regularly at the base of uninuclear conidia. Microtubule inhibitor methyl benzimidazol-2-ylcarbamate disintegrated the microtubules, and inhibited nuclear division, development of hyphae and conidiogenesis. Actin inhibitor Cytochalasin D induced swelling of hyphal apexes and developing conidia. This inhibitory activity ceased after 5 to 12 h when the occasional septa appeared and conidiogenesis was completed. The lack of unicellular organization in multinucleate hyphae of A. pullulans seems be related to a rarity of F-actin structures: i.e. absence of actin cables, the lack of actin cytokinetic rings in particular, resulting in the uncoupling of the nuclear division from cytokinesis; the association of both processes is, however, retained during conidiogenesis.

Actins↗
PubMed2003

EST analysis of genes expressed by the zygomycete pathogen Conidiobolus coronatus during growth on insect cuticle.

Conidiobolus coronatus (Zygomycota) is a facultative saprobe that is a pathogen of many insect species. Almost 2000 expressed sequence tag (EST) cDNA clones were sequenced to analyse gene expression during growth on insect cuticle. Sixty percent of the ESTs that could be clustered into functional groups (E<or=10(-5)) had their best BLAST hits among fungal sequences. These included chitinases and multiple subtilisins, trypsin, metalloprotease and aspartyl protease activities with the potential to degrade host tissues and disable anti-microbial peptides. Otherwise, compared to the ascomycete entomopathogen Metarhizium anisopliae, Con. coronatus produced many fewer types of hydrolases (e.g. no phospholipases), antimicrobial agents, toxic secondary metabolites and no ESTs with putative roles in the generation of antibiotics. Instead, Con. coronatus produced a much higher proportion of ESTs encoding ribosomal proteins and enzymes of intermediate metabolism that facilitate its rapid growth. These results are consistent with Con. coronatus having adapted a modification of the saprophytic ruderal-selected strategy, using rapid growth to overwhelm the host and exploit the cadaver before competitors overrun it. This strategy does not preclude specialization to pathogenicity, as Con. coronatus produces the greatest complexity of proteases on insect cuticle, indicating an ability to respond to conditions in the cuticle.

Animals↗