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PubMed1975

Autolytic enzymes in hyphae of Aspergillus nidulans: their action on old and newly formed walls.

Walls, purified from hyphae of the ascomycete Aspergillus nidulans, autolyzed on incubation and liberated glucose, mannose, galactose, N-acetylglucosamine, and soluble oligosaccharides. Digestion proceeded at linear rates until approximately 3% of the wall polymers had been hydrolyzed and then slowed markedly. The change in the rate of autolysis was not due to loss of enzyme activity but was caused by the disappearance of a fraction of the wall which was highly susceptible to digestion. Radioactive labeling showed that this fraction was the newly formed wall. The new wall was highly susceptible to enzyme action both when it was deposited at the apex in growing hyphae or when deposited laterally in hyphae treated with cycloheximide. The relations between wall modification and apical growth are discussed.

Aspergillus nidulans↗
PubMed1975

Kynureninase-Type enzymes of Penicillum roqueforti, Aspergillus niger, Rhizopus stolonifer, and Pseudomonas fluorescens: further evidence for distinct kynureninase and hydroxykynureninase activities.

The kynureninase-type enzymes of three fungi and one bacterium were isolated and examined kinetically for their ability to catalyze the hydrolysis of L-kynurenine and L-3-hydroxykynurenine. The phycomycete Rhizopus stolonifer was found to contain a single, constitutive enzyme with Km for L-3-hydroxykynurenine and L-kynurenine of 6.67 times 10-minus 6 and 2.5 times 10-minus 4 M, respectively. The ascomycetes Aspergillus niger and Penicillium roqueforti each contain an enzyme, induced by L-tryptophan, with similar Km for L-3-hydroxykynurenine and L-kynurenine ranging from 5.9 times 10-minus 5 to 14.3 times 10-minus 5 M, as well as a constitutive enzyme with Km for the two substrates of similar to 4 times 10-minus 6 M and 10-minus 4 M. The bacterium Pseudomonas fluorescens has a single, inducible enzyme with Km for L-3-hydroxykynurenine and L-kynurenine of 5 times 10-minus 4 and 7 times 10-minus 5 M. In addition, significant differences in maximal velocities (Vmax) were observed in two cases. The Vmax of the inducible activity from P. fluorescens was 4.5 times greater for L-kynurenine than L-3-hydroxykynurenine, whereas the Vmax of the constitutive activity from R. stolonifer was 2.5 times greater for L-3-hydroxykynurenine. It is concluded (i) that the constitutive activities are hydroxykynureninases involved in the biosynthesis of nicotinamide adenine dinucleotide from L-tryptophan, (ii) that the inducible activities are kynureninases involved in the catabolism of L-tryptophan to anthranilate, and (iii) that R. stolonifer and P. fluorescens, respectively, carry the most specific examples of each type of enzyme.

Ammonium Sulfate↗
PubMed1981

Dominant spore color mutants of Aspergillus nidulans defective in germination and sexual development.

The ascomycete Aspergillus nidulans produces green conidia (asexual spores). Recessive mutants which produce yellow conidia have been previously isolated from haploid strains and have been shown to be deficient in laccase (diphenol oxidase), an enzyme that requires copper for activity. Using a diploid parent strain, we isolated dominant yellow conidial mutants which, in the haploid state, produced even less laccase activity than a recessive mutant. Three isolates of such mutants behaved similarly and define a single complementation group (yB) on chromosome VIII distinct from the yA locus on chromosome I defined by recessive mutants. Unlike yA mutants, whose only discernable phenotype is their conidial color, yB mutants are pleiotropic: conidial germination was delayed relative to the wild type, and sexual development was blocked at an early stage. The three phenotypes of yB mutants were expressed on yeast extract-glucose medium containing 1.6 microM of added copper. When copper was added to above 5 microM, all three phenotypes were remediated, and near wild-type levels of laccase were produced. We conclude that yB mutants have a reduced availability of copper. The dominance of yB mutants could result, for example, from an alteration in transport or storage of copper. Using an immunological assay, we detected no laccase antigenic cross-reacting material in yB mutants grown on medium of low copper content. We conclude that either the synthesis or the stability of laccase is copper dependent.

Aspergillus nidulans↗
PubMed1987

Podospora anserina does not senesce when serially passaged in liquid culture.

A procedure was developed for the prolonged growth of the ascomycete fungus Podospora anserina in liquid culture to determine the effects of such growth on the senescence phenotype. Senescence in P. anserina, which is maternally inherited and associated with the excision and amplification of specific mitochondrial plasmids, occurs when this species is grown on solid medium. In two independent experiments no evidence of senescence was observed as mycelia were serially passaged in liquid culture. Further, when separable mycelial masses, termed puff balls, from the liquid cultures were plated on solid medium, a significant increase in their average longevity was observed. The apparent immortality of P. anserina in liquid culture was not dependent upon mitochondrial DNA rearrangements, nor was it affected by the presence of a previously described senescence plasmid, alpha senDNA. Evidence was obtained indicating that growth in liquid culture exerts selective pressure to maintain the wild-type mitochondrial genome.

Ascomycota↗
PubMed1989

Cloning of 18S and 25S rDNAs from the pathogenic fungus Cryptococcus neoformans.

Cryptococcus neoformans is an important pathogenic fungus that has been classified as a basidiomycete. Little is known of the molecular genetics of this fungal pathogen. To begin such studies, we devised a procedure for extraction of DNA from cryptococci; this method involved the use of the cell wall-active enzyme NovoZym 234. Using cloned rDNA of Saccharomyces cerevisiae as a probe, we identified homologous restriction fragments in a Southern blot of digested C. neoformans DNA. An 8.6-kilobase HindIII fragment that hybridized with the yeast rDNA probe was ligated with the vector pBR322 and cloned into Escherichia coli. When the fragment was used as a probe, it hybridized to the 18S and 25S rRNAs of C. neoformans in Northern (RNA) blots of native and denatured RNA. It bound at high stringency only weakly to the rRNAs of the ascomycete S. cerevisiae. The locations of the genes for 5/5.8S, 18S, and 25S subunits in the cloned fragment were identified with labeled rRNA of these different types.

Blotting, Northern↗
PubMed1989

Isolation and characterization of a laccase-derepressed mutant of Neurospora crassa.

Laccase from the ascomycete Neurospora crassa is an inducible secretory enzyme. Production of this enzyme is repressed in vegetative cultures but can be induced by treatment with low concentrations of cycloheximide. Isolation and characterization of a derepressed mutant, the lah-1 mutant, that is capable of producing laccase in vegetative cultures without induction by cycloheximide are described. The lah-1 mutation is mapped between nit-2 and leu-3 on linkage group I, and it behaved as a recessive mutation in a forced heterokaryon. No differences were detected biochemically or immunologically between the laccase protein produced by the lah-1 mutant in the absence of cycloheximide and that induced with cycloheximide in the wild-type strain. This suggests that both laccases (66 kilodaltons) are products of the same structural gene. Relative amounts of laccase in the culture filtrate of the lah-1 mutant were much higher than those induced with cycloheximide in the wild-type strain, demonstrating high efficiency of the lah-1 mutant in production and secretion of laccase. The time course of laccase production by the lah-1 mutant revealed that expression of 66-kilodalton laccase was repressed in conidia and derepressed during vegetative mycelial growth. This suggests that a multiple regulatory mechanism is involved in the production and/or maturation of Neurospora laccase. The lah-1 mutant may be useful for identifying genes that regulate expression of the laccase gene in N. crassa.

Chromatography↗
PubMed1990

Sequence analysis and expression of the two genes for elongation factor 1 alpha from the dimorphic yeast Candida albicans.

Two Candida albicans genes that encode the protein synthesis factor elongation factor 1 alpha (EF-1 alpha) were cloned by using a heterologous TEF1 probe from Mucor racemosus to screen libraries of C. albicans genomic DNA. Sequence analysis of the two clones showed that regions of DNA flanking the coding regions of the two genes were not homologous, verifying the presence of two genes, called TEF1 and TEF2, for EF-1 alpha in C. albicans. The coding regions of TEF1 and TEF2 differed by only five nucleotides and encoded identical EF-1 alpha proteins of 458 amino acids. Both genes were transcribed into mRNA in vivo, as shown by hybridization of oligonucleotide probes, which bound specifically to the 3' nontranslated regions of TEF1 and TEF2, respectively, to C. albicans total RNA in Northern (RNA) blot analysis. The predicted EF-1 alpha protein of C. albicans was more similar to Saccharomyces cerevisiae EF-1 alpha than to M. racemosus EF-1 alpha. Furthermore, codon bias and the promoter and termination signals of the C. albicans EF-1 alpha proteins were remarkably similar to those of S. cerevisiae EF-1 alpha. Taken together, these results suggest that C. albicans is more closely related to the ascomycete S. cerevisiae than to the zygomycete M. racemosus.

Amino Acid Sequence↗
PubMed1996

Global changes in protein composition of N2-fixing-Azoarcus sp. strain BH72 upon diazosome formation.

The strictly respiratory, diazotrophic bacterium Azoarcus sp. strain BH72 fixes nitrogen under microaerobic conditions. In empirically optimized batch cultures at nanomolar O2 concentrations in the presence of proline, cells can shift into a state of higher activity and respiratory efficiency of N2 fixation in which intracytoplasmic membrane stacks (diazosomes) related to N2 fixation are formed. Induction of intracytoplasmic membranes is most pronounced in coculture of Azoarcus sp. strain BH72 with an ascomycete originating from the same host plant, Kallar grass. To initiate studies on function of diazosomes and regulation of their formation, diazosome-containing bacteria were compared with respect to composition or total cellular and membrane proteins with diazosome-free cells fixing nitrogen under standard conditions. In two-dimensional protein gels, we detected striking differences in protein patterns upon diazosome formation: (i) 7.3% of major proteins disappeared, and only 73% of the total proteins of control cells were detectable, indicating that diazosome-containing cells have a more specialized metabolism; (ii) nine new proteins appeared and five proteins increased in concentration, designated DP1 to DP 15; and (iii) five new major membrane proteins (MP1 to MP6) were detected, indicating that membranes might have specialized functions. N-terminal amino acid sequence analysis of DP1 to DP4 allowed us to preliminarily identify DP4 as the glnB gene product P(II), an intracellular signal transmitter known to be involved in the regulation of nitrogen metabolism. According to its electrophoretic mobility, it might be uridylylated in diazosome-free cells but not in diazosome-containing cells, or it may represent a second, not identical P(II) protein. Oligonucleotides deduced from N-terminal sequences of DP1 and DP4 specifically hybridized to chromosomal DNA of Azoarcus sp. strain BH72 in Southern hybridizations.

Bacterial Proteins↗
PubMed1999

Characterization of a novel, antifungal, chitin-binding protein from Streptomyces tendae Tü901 that interferes with growth polarity.

The afp1 gene, which encodes the antifungal protein AFP1, was cloned from nikkomycin-producing Streptomyces tendae Tü901, using a nikkomycin-negative mutant as a host and screening transformants for antifungal activity against Paecilomyces variotii in agar diffusion assays. The 384-bp afp1 gene has a low G+C content (63%) and a transcription termination structure with a poly(T) region, unusual attributes for Streptomyces genes. AFP1 was purified from culture filtrate of S. tendae carrying the afp1 gene on the multicopy plasmid pIJ699. The purified protein had a molecular mass of 9,862 Da and lacked a 42-residue N-terminal peptide deduced from the nucleotide sequence. AFP1 was stable at extreme pH values and high temperatures and toward commercial proteinases. AFP1 had limited similarity to cellulose-binding domains of microbial plant cell wall hydrolases and bound to crab shell chitin, chitosan, and cell walls of P. variotii but showed no enzyme activity. The biological activity of AFP1, which represents the first chitin-binding protein from bacteria exhibiting antifungal activity, was directed against specific ascomycetes, and synergistic interaction with the chitin synthetase inhibitor nikkomycin inhibited growth of Aspergillus species. Microscopy studies revealed that fluorescein-labeled AFP1 strongly bound to the surface of germinated conidia and to tips of growing hyphae, causing severe alterations in cell morphogenesis that gave rise to large spherical conidia and/or swollen hyphae and to atypical branching.

Amino Acid Sequence↗
PubMed2001

Role of a ferredoxin gene cotranscribed with the nifHDK operon in N(2) fixation and nitrogenase "switch-off" of Azoarcus sp. strain BH72.

The endophytic diazotroph Azoarcus sp. strain BH72 is capable of infecting rice roots and of expressing the nitrogenase (nif) genes there. In order to study the genetic background for nitrogen fixation in strain BH72, the structural genes of nitrogenase (nifHDK) were cloned and sequenced. The sequence analysis revealed an unusual gene organization: downstream of nifHDK, a ferredoxin gene (fdxN; 59% amino acid sequence identity to R. capsulatus FdxN) and open reading frames showing 52 and 36% amino acid sequence identity to nifY of Pseudomonas stutzeri A15 and ORF1 of Azotobacter vinelandii were located. Northern blot analysis, reverse transcriptase PCR and primer extension analysis revealed that these six genes are located on one transcript transcribed from a sigma(54)-type promoter. Shorter transcripts sequentially missing genes of the 3' part of the full-length mRNA were more abundantly detected. Mutational analyses suggested that FdxN is an important but not the essential electron donor for dinitrogenase reductase. An in-frame deletion of fdxN resulted in reduced growth rates (59% +/- 9%) and nitrogenase activities (81%) in nitrogen-fixing pure cultures in comparison to the wild type. Nitrogenase activity was fully complemented in an fdxN mutant which carried a nifH promoter-driven fdxN gene in trans. Also, in coculture with the ascomycete Acremonium alternatum, where strain BH72 develops intracytoplasmic membrane stacks, the nitrogenase activity in the fdxN deletion mutant was decreased to 56% of the wild-type level. Surprisingly, the fdxN deletion also had an effect on the rapid "switch-off" of nitrogenase activity in response to ammonium. Wild-type strain BH72 and the deletion mutant complemented with fdxN in trans showed a rapid reversible inactivation of acetylene reduction, while the deletion mutant did not cease to reduce acetylene. In concordance with the hypothesis that changes in the redox state of NifH or electron flux towards nitrogenase may be involved in the mechanism of physiological nitrogenase switch-off, our results suggest that the ferredoxin may be a component involved in this process.

Azoarcus↗
PubMed1968

Nucleotide composition of nuclear and mitochondrial deoxyribonucleic acid of fungi.

The buoyant density of nuclear and mitochondrial deoxyribonucleic acid (DNA) from 14 species of fungi was determined by CsCl density gradient equilibrium centrifugation. The buoyant density of both types of DNA was the same for all three Mucorales analyzed. The buoyant density of mitochondrial DNA was significantly lower than that of the nuclear DNA for nine species of Ascomycetes and two species of Basidiomycetes. No simple correlation could be obtained from the comparison of the two types of DNA. Mitochondrial DNA represented a very small proportion of total DNA. Heat-denatured mitochondrial DNA renatured more readily than nuclear DNA.

Ascomycota↗
PubMed1969

Organization of enzymes in the common aromatic synthetic pathway: evidence for aggregation in fungi.

Centrifugation in sucrose density gradients of partially purified extracts from six species of fungi, i.e., Rhizopus stolonifer, Phycomyces nitens, Absidia glauca (Phycomycetes), Aspergillus nidulans (Ascomycetes), Coprinus lagopus, and Ustilago maydis (Basidiomycetes), indicate that the five enzymes catalyzing steps two to six in the prechorismic acid part of the polyaromatic synthetic pathway sediment together. The sedimentation coefficients for these enzymes are very similar in the six species and are comparable to those previously observed for the multienzyme complexes (arom aggregates) of Neurospora crassa and Saccharomyces cerevisiae. These results are interpreted as indicating the presence in each of these fungi of arom aggregates, presumably encoded by arom gene clusters similar to those in N. crassa and S. cerevisiae. Evidence has also been obtained for the presence in two species (A. nidulans and U. maydis) and the absence in the other four species of a second dehydroquinase isozyme which is distinguishable from the synthetic activity on the basis of both thermostability tests and S values. This second dehydroquinase, which is apparently involved in the catabolism of quinic acid via a pathway similar to that in N. crassa, is inducible in A. nidulans (as it is in N. crassa), but constitutive in U. maydis. These comparative findings are discussed in relation to the organization, evolution, and possible functional relationships of synthetic and catabolic aromatic pathways in fungi.

Alcohol Oxidoreductases↗
PubMed1990

Occurrence of Clavispora lusitaniae, the teleomorph of Candida lusitaniae, among clinical isolates.

Of 13 clinical isolates of Candida lusitaniae from diverse geographical regions, 7 represented the mating types (6 alpha, 1 a) of the ascomycete Clavispora lusitaniae. Selected nonfertile isolates showed significant DNA relatedness (greater than 90%) to representatives of both mating types. Phenotypic physiological characteristics, such as cellobiose fermentation and rhamnose assimilation, proved insufficient for separation of Clavispora lusitaniae and Clavispora opuntiae.

Candida↗
PubMed1993

The benomyl test as a fundamental diagnostic method for medical mycology.

The fungicide benomyl has long been known to differentially affect major taxonomic groups of fungi. In the present study 163 species or aggregates of closely similar species of medically important fungi and actinomycetes, as well as species commonly isolated as clinical contaminants, were tested to determine their reactions to three concentrations of benomyl. Fungi of basidiomycetous, endomycetous, and microascaceous affinities were highly resistant, including all common yeasts and Geotrichum, Pseudallescheria, Scedosporium, and Scopulariopsis species. Also resistant were fungi of pleosporalean affinities with poroconidial anamorphs, such as Alternaria, Bipolaris, Curvularia, and Exserohilum species. Most other fungi of ascomycetous affinity were moderately to strongly susceptible. Such fungi included dermatophytes; Coccidioides, Blastomyces, and Histoplasma species; Sporothrix schenckii; medically important aspergilli; and "black yeasts." Benomyl testing aided in the provisional identification of nonsporulating mycelia, including common basidiomycetous isolates obtained as contaminants as well as nonsporulating Aspergillus fumigatus from pulmonary sources.

Actinomycetales↗
PubMed1994

First report of involvement of Nodulisporium species in human disease.

Allergic fungal sinusitis is a common disease that results from a hypersensitivity reaction mounted by the host against fungi living in the paranasal sinuses. We have recently treated a patient with allergic fungal sinusitis due to a Nodulisporium species. This is the first description of a Nodulisporium species involved in human disease. The genus Nodulisporium contains both dematiaceous and nondematiaceous members. These fungi occur worldwide in nature, often as accompanying conidial anamorphs of certain wood decay ascomycetes. Clinical mycology laboratories may encounter this new agent of phaeohyphomycosis.

Adult↗
PubMed1995

Disseminated Microascus cirrosus infection in pediatric bone marrow transplant recipient.

Microascus cirrosus Curzi and its associated anamorphic state, Scopulariopsis, were recovered from the cutaneous lesion of a 12-year-old male who had undergone an autologous bone marrow transplantation for acute myelogenous leukemia. Histopathology sections from the biopsied lesion demonstrated septate hyphae consistent with a fungal etiology. Radiographic studies of the lungs subsequent to progression of the lesion revealed a consolidation in the right upper lobe suggesting a primary focus of infection. While M. cirrosus is fairly abundant in nature and widely distributed in stored grains in North America, this is, to our knowledge, the first reported human infection by this species. Salient characteristics for the identification of this dematiaceous ascomycete, M. cirrosus, will be presented.

Ascomycota↗
PubMed1995

Analysis of genes coding for small-subunit rRNA sequences in studying phylogenetics of dematiaceous fungal pathogens.

Because of their ability to display yeast-like growth forms in various environmental conditions, dematiaceous (melanized) hyphomycetes of the form-genera Exophiala, Rhinocladiella, and Wangiella have been informally termed "black yeasts." Cladistic analysis of 1,050 bp of the genes coding for small-subunit rRNA (SSU rDNA) supported a close relationship among species of these black yeasts with other dematiaceous hyphomycetes in the form-genera Fonsecaea, Phialophora, and Ramichloridium. The conventional categories of these fungi based on asexual states are not supported by phylogenetic analysis of SSU rDNA sequences. Isolates exhibiting annellidic modes of blastic conidiogenesis (e.g., Exophiala spp.) were not monophyletic and were placed as sister taxa to isolates that produce phialides or sympodulae. The results indicated very close relationships between isolates of Wangiella dermatitidis and Exophiala mansonii and between Rhinocladiella aquaspersa and Exophiala jeanselmei. This clade of dematiaceous hyphomycetes was a sister group to a clade comprising members of two orders of cleistothecial ascomycetes, Eurotiales and Onygenales. The etiological agents of chromoblastomycosis were found to be a closely related group (clade), while the agents of phaeohyphomycosis displayed a broader distribution on the SSU rDNA tree.

Ascomycota↗
PubMed1998

Molecular genetic variation in Emmonsia crescens and Emmonsia parva, etiologic agents of adiaspiromycosis, and their phylogenetic relationship to Blastomyces dermatitidis (Ajellomyces dermatitidis) and other systemic fungal pathogens.

Emmonsia crescens, an agent of adiaspiromycosis, Blastomyces dermatitidis, the agent of blastomycosis, and Histoplasma capsulatum, the agent of histoplasmosis, are known to form meiotic (sexual) stages in the ascomycete genus Ajellomyces (Onygenaceae, Onygenales), but no sexual stage is known for E. parva, the type species of the genus Emmonsia. To evaluate relationships among members of the putative Ajellomyces clade, large-subunit ribosomal and internal transcribed spacer region DNA sequences were determined from PCR-amplified DNA fragments. Sequences were analyzed phylogenetically to evaluate the genetic variation within the genus Emmonsia and evolutionary relationships to other taxa. E. crescens and E. parva are distinct species. E. crescens isolates are placed into two groups that correlate with their continents of origin. Considerable variation occurred among isolates previously classified as E. parva. Most isolates are placed into two closely related groups, but the remaining isolates, including some from human sources, are phylogenetically distinct and represent undescribed species. Strains of B. dermatitidis are a sister species of E. parva. Paracoccidioides brasiliensis and Histoplasma capsulatum are ancestral to most Emmonsia isolates, and P. brasiliensis, which has no known teleomorph, falls within the Ajellomyces clade.

Blastomyces↗