Spore productivity in Cladosporium

The high incidence ofCladosporia in the airspora indicates a prolific production of spores. Six species ofCladosporium were sampled over a period of 9 weeks, using dry and wet (mist-laden) air, and over a period of 4 weeks using humid air. Many more spores were released in wet air than in dry air: numbers released in humid air were generally intermediate between those of wet and dry samples. None of the cultures was exhausted of spores at the end of the sampling periods although samples generally decreased in size from the fifth or sixth week onwards. Removal of spores would seem to be conducive to further sporulation provided the substrate is not exhausted. Maximum productivities recorded for the six species (all in mist-laden air) ranged from 730 to 26 100 spores per mg dry weight of mycelium. Differences in the levels of spore production in culture by the six species do not correlate with their individual frequencies in the airspora, indicating that the latter are more dependent on the distribution and substrate relationships of each species.     

Xerotolerant Cladosporium sphaerospermum Are Predominant on Indoor Surfaces Compared to Other Cladosporium Species

Indoor fungi are a major cause of cosmetic and structural damage of buildings worldwide and prolonged exposure of these fungi poses a health risk. Aspergillus, Penicillium and Cladosporium species are the most predominant fungi in indoor environments. Cladosporium species predominate under ambient conditions. A total of 123 Cladosporium isolates originating from indoor air and indoor surfaces of archives, industrial factories, laboratories, and other buildings from four continents were identified by sequencing the internal transcribed spacer (ITS), and a part of the translation elongation factor 1α gene (TEF) and actin gene (ACT). Species from the Cladosporium sphaerospermum species complex were most predominant representing 44.7% of all isolates, while the Cladosporium cladosporioides and Cladosporium herbarum species complexes represented 33.3% and 22.0%, respectively. The contribution of the C. sphaerospermum species complex was 23.1% and 58.2% in the indoor air and isolates from indoor surfaces, respectively. Isolates from this species complex showed growth at lower water activity (≥ 0.82) when compared to species from the C. cladosporioides and C. herbarum species complexes (≥ 0.85). Together, these data indicate that xerotolerance provide the C. sphaerospermum species complex advantage in colonizing indoor surfaces. As a consequence, C. sphaerospermum are proposed to be the most predominant fungus at these locations under ambient conditions. Findings are discussed in relation to the specificity of allergy test, as the current species of Cladosporium used to develop these tests are not the predominant indoor species.     

Utilization of n-Alkanes by Cladosporium resinae

Four different isolates of Cladosporium resinae from Australian soils were tested for their ability to utilize liquid n-alkanes ranging from n-hexane to n-octadecane under standard conditions. The isolates were unable to make use of n-hexane, n-heptane, and n-octane for growth. In fact, these hydrocarbons, particularly n-hexane, exerted an inhibitory effect on spore germination and mycelial growth. All higher n-alkanes from n-nonane to n-octadecane were assimilated by the fungus, although only limited growth occurred on n-nonane and n-decane. The long chain n-alkanes (C(14) to C(18)) supported good growth of all isolates, but there was no obvious correlation between cell yields and chain lengths of these n-alkanes. Variation in growth responses to individual n-alkane among the different isolates was also observed. The cause of this variation is unknown.     

Epidemiology of Cladosporium allii and Cladosporium allii-cepae, leaf blotch pathogens of leek and onion.

Conidia of Cladosporium allii and C. allii-cepae germinated over the temperature range 2–30°C on agar with optimal responses at 15–20°C (C. allii) and 20°C (C. allii-cepae). Conidia of both fungi germinated in water and at c. 100% relative humidity (r.h.) but not at lower humidities on leaf and glass slide surfaces. Germination was more rapid when spores were applied dry to agar or leaves than when applied in water or nutrient solution. More lesions developed when conidia of C. allii-cepae were deposited dry on onion leaf discs or leaf surfaces than when they were applied suspended in water. Conidia of both fungi required 18–20 h at c. 100% r.h. to germinate and infect when applied dry to leaves. Damaging the leaves or the addition of nutrients to the leaf surface increased the incidence of infection by C. allii-cepae compared to controls. Inoculated onion bait plants placed out-of-doors developed infection after at least 17 h at c. 100% r.h. or with leaf wetness. Similar conditions were necessary for infection of bait plants exposed in onion and leek crops infected by C. allii-cepae and C. allii respectively. Disease development and spread of infection occurred at different rates over the same period in two different cultivars of leeks, with spore concentrations increasing in proportion to disease. Spore numbers in the air fell considerably when infected leeks were ploughed under.     

Characterization of Dimorphism in Cladosporium werneckii

Yeast forms of the dimorphic fungus Cladosporium werneckii grow by polar budding and yield a homogeneous yeast phase when cultured at 21 C in an agitated sucrose-salts medium (Czapek-Dox broth). Yeast extract enrichment of such a yeast phase consisting of 10⁴ yeasts per ml induces a quantitative conversion of the yeasts to true hyphae. This conversion is not mediated by a transition cell and is often attended by capsule formation. When 10⁵ or 10⁶ yeasts per ml receive enrichment, a nonquantitative conversion to moniliform hyphae is effected and no capsule formation is observed. Rapid agitation compared to slow agitation or stationary incubation of the nutritionally mediated conversion cultures greatly accelerates the production of lateral hyphal buds or their yeast progenies. These cells appear incapable of undergoing nutritional conversion to hyphae, but instead must grow for several generations in the unenriched sucrose-salts medium to restore conversion competence. Temperature shifts affect directly the morphology and morphogenesis of the yeast in unenriched medium; at 17 C yeasts are smaller and more ovoid than at 21 C, and at 30 C marked conversion of yeasts to moniliform hyphae occurs. A methodology employing the Coulter counter and Coulter channelizer provides evidence that direct correlations do not always exist between the optimum conditions for the growth of C. werneckii and the optimum conditions for its yeast-to-mold conversion.     

Production of biosurfactants by Cladosporium resinae

Summary Cladosporium resinae produces extracellular biosurfactants when growing in a hydrocarbon source such as the jet fuel JP8. This production of biosurfactants was observed by the reduction of the surface tension of the aqueous phase of growing medium, and by the increase in emulsion and foaming properties. A partial purification by collapsed foam gave better physical properties by decreasing surface tension and increasing foaming power and stabilization of emulsions. Surface active substances were purified by reversed phase chromatography. Six compounds representing over 75% of fraction containing surface activity were present. This fraction gave an improvement of all surface properties.     

Pathway of n-Alkane Oxidation in Cladosporium resinae

Pathways of initial oxidation of n-alkanes were examined in two strains of Cladosporium resinae. Cells grow on dodecane and hexadecane and their primary alcohol and monoic acid derivatives. The homologous aldehydes do not support growth but are oxidized by intact cells and by cell-free preparations. Hexane and its derivatives support little or no growth, but cell extracts oxidize hexane, hexanol, and hexanal. Alkane oxidation by extracts is stimulated by reduced nicotinamide adenine dinucleotide (phosphate). Alcohol and aldehyde oxidation are stimulated by nicotinamide adenine dinucleotide (phosphate), and reduced coenzymes accumulate in the presence of cyanide or azide. Extracts supplied with (14)C-hexadecane convert it to the alcohol, aldehyde, and acid. Therefore, the major pathway for initial oxidation of n-alkanes is via the primary alcohol, aldehyde, and monoic acid, and the system can act on short-, intermediate-, and long-chain substrates. Thus, filamentous fungi appear to oxidize n-alkanes by pathways similar to those used by bacteria and yeasts.     

Toluene monooxygenase from the fungus Cladosporium sphaerospermum

Assimilation of toluene by Cladosporium sphaerospermum is initially catalyzed by toluene monooxygenase (TOMO). TOMO activity was induced by adding toluene to a glucose-pregrown culture of C. sphaerospermum. The corresponding microsomal enzyme needed NADPH and O(2) to oxidize toluene and glycerol, EDTA, DTT, and PMSF for stabilization. TOMO activity was maximal at 35 degrees C and pH 7.5 and was inhibited by carbon monoxide, Metyrapone, and cytochrome c. TOMO preferred as substrates also other aromatic hydrocarbons with a short aliphatic side chain. Its reduced carbon monoxide difference spectrum showed a maximum at 451 nm. A substrate-induced Type I spectrum was observed on addition of toluene. These results indicated that TOMO is a cytochrome P450. TOMO and its corresponding reductase were eventually purified by a simultaneous purification revealing apparent molecular masses of 58 and 78 kDa, respectively.     

alpha-Amylase inhibitor from fungus Cladosporium herbarum F-828

A strain of fungus Cladosporium herbarum extracellularly produced an inhibitor specific for mammalian alpha-amylase. The inhibitor was purified 81-fold by freeze-thawing, heat treatment, and column chromatography on DEAE-cellulose, Sephadex G-75, DEAE-Sephacel, and Bio-Gel P-100. An apparent molecular weight of approximately 18,000 was estimated for the inhibitor using Bio-Gel P-100 filtration. The purified inhibitor preparation was a glycoprotein containing about 10% carbohydrate. The amino acid analysis of the inhibitor showed abundances of Gly, Asp, Glu, Ser, Ala, and Thr residues. The inhibitor was stable between pH 5 and 12 at 4 degrees C, and below 80 degrees C at pH 7.0. A binary complex formation out of equimolar amounts of the inhibitor and alpha-amylase, was demonstrated by polyacrylamide gel electrophoresis, and Bio-Gel P-100 chromatography. Kinetic studies exhibited that the inhibitor noncompetitively inhibited the enzyme reaction with a Ki value of 2.3 approximately 4.8 x 10(-10) M, by combining with the enzyme molecule at a different site from the substrate binding site.     

Hansfordia pulvinata,mycoparasite destructeur du Cladosporium fulvum

Résumé LeHansfordia pulvinata a été observé sur feuilles de tomate où sa présence est liée aux thalles duCladosporium fulvum. Il se comporte en parasite à l'égard de ce champignon phytopathogène: ses rameaux télémorphiques terminés en appressorium enserrent les hyphes et les chaînes de spores de son hôte et les tuent. Dès le contact, la croissance du mycoparasite s'accélère, il recouvre les thalles duCladosporium (lui-même freiné par les substances fongistatiques émises) et gêne la dissémination de ses propagules.L'effet néfaste pour leC. fulvum de cette interaction ainsi que certains caractères biologiques duH. pulvinata (notamment la dissémination aisée de ses abondantes xérospores et leur aptitude à la germination en conditions difficiles, ses exigences thermiques) nous font penser que cette espèce mycoparasite pourrait être utilisée comme agent de lutte biologique contre la cladosporiose de la tomate en serre.     

Molecular characterization of benzimidazole-resistant isolates of Cladosporium fulvum

The benzimidazole fungicide thiophanate-methyl is commonly applied to control leaf mould of tomato caused by Cladosporium fulvum in China. In this study, 32 isolates of C. fulvum were examined for their sensitivities to thiophanate-methyl, and two benzimidazole-resistant (BenR) phenotypes BenR1 and BenR2 were identified. The BenR1 isolates were resistant to thiophanate-methyl, but were more sensitive to the phenylcarbamate fungicide diethofencarb than the wild-type isolates. The BenR2 isolates resistant to thiophanate-methyl were insensitive to diethofencarb. All tested isolates were sensitive to the dicarboximide fungicide iprodione. The complete beta-tubulin gene was isolated from this fungus to study its potential role in benzimidazole resistance. Analysis of the DNA sequence of the beta-tubulin gene showed that the BenR1 isolates had a point mutation at codon 198, causing a substitution of glutamic acid to alanine. In the BenR2 isolates, a point mutation at codon 200 causing a substitution of phenylalanine to tyrosine was detected. Based on these point mutations, a multiplex allele-specific PCR method was developed successfully for the first time to detect two point mutations at the beta-tubulin gene simultaneously in single PCR amplifications.