Cephalotrichum and related synnematous fungi with notes on species from the built environment

A recent taxonomic revision of Microascaceae with an emphasis on synnematous fungi enabled re-identification of previously isolated indoor strains of Cephalotrichum. All available Cephalotrichum strains from the culture collection of the Westerdijk Institute were studied, 20 originating from the built environment. Phylogenetic relationships were inferred from DNA sequence data from the internal transcribed spacer 1 and 2 and intervening 5.8S nrDNA (ITS), and parts of β-tubulin (tub2) and translation elongation factor 1-α (tef1) genes. Additionally, herbarium material of 14 Cephalotrichum species described from soil in China was studied, and the taxonomy of C. album, not considered in recent revisions, was reevaluated. Sixteen phylogenetic species in Cephalotrichum are distinguished, five described as new species: C. domesticum, C. lignatile, C. telluricum, C. tenuissimum and C. transvaalense. Five Cephalotrichum species occur in the built environment: C. domesticum, C. gorgonifer (formerly known as Trichurus spiralis), C. microsporum, C. purpureofuscum, and C. verrucisporum. Based on the number of isolates, C. gorgonifer (nine strains) is the most common indoor species. The study of the Chinese herbarium material resulted in the acceptance of three additional Cephalotrichum species: C. casteneum, C. ellipsoideum, and C. spirale. Four species are considered nomena dubia (C. cylindrosporum, C. macrosporum, C. ovoideum, and C. robustum), five are placed in synonymy with other Cephalotrichum species (C. acutisporum, C. inflatum, C. longicollum, C. oblongum, C. terricola) and one species, C. verrucipes, is probably a synonym of Penicillium clavigerum. Cephalotrichum columnare, former Doratomyces columnaris, is transferred to Kernia. Cephalotrichum album, formerly known as Doratomyces putredinis, is transferred to Acaulium and redescribed.

Phylogeny and taxonomic revision of Microascaceae with emphasis on synnematous fungi

The taxonomy of the synnematous genera Cephalotrichum, Doratomyces and Trichurus, and other related genera Gamsia, Wardomyces and Wardomycopsis, has been controversial and relies mainly on morphological criteria. These are microascaceous saprobic fungi mostly found in air and soil and with a worldwide distribution. In order to clarify their taxonomy and to delineate generic boundaries within the Microascaceae, we studied 57 isolates that include clinical, environmental and all the available ex-type strains of a large set of species by means of morphological, physiological and molecular phylogenetic analyses using DNA sequence data of four loci (the ITS region, and fragments of rDNA LSU, translation elongation factor 1α and β-tubulin). The results demonstrate that Cephalotrichum, Doratomyces and Trichurus are congeneric and the genus Cephalotrichum is accepted here with Echinobotryum as a further synonym. The genera Acaulium and Fairmania, typified by A. albonigrescens and F. singularis, respectively, are distinct from Microascus and Scopulariopsis, Gamsia is distinct from Wardomyces, and Wardomycopsis is confirmed as a separate genus in the Microascaceae. Two new species of Cephalotrichum are described as C. brevistipitatum and C. hinnuleum. Nine new combinations are proposed, i.e. Acaulium acremonium, A. caviariforme, Cephalotrichum asperulum, C. columnare, C. cylindricum, C. dendrocephalum, C. gorgonifer, Gamsia columbina and Wardomyces giganteus. A neotype is designed for C. stemonitis. Lectotypes and epitypes are designated for A. acremonium, A. albonigrescens, C. gorgonifer, C. nanum and W. anomalus. Cephalotrichum cylindricum, C. microsporum, F. singularis and Gamsia columbina are also epitypified with new specimens. Descriptions of the phenotypic features and dichotomous keys for identification are provided for accepted species in the different genera.

Valproic Acid Induces Antimicrobial Compound Production in Doratomyces microspores

One of the biggest challenges in public health is the rising number of antibiotic resistant pathogens and the lack of novel antibiotics. In recent years there is a rising focus on fungi as sources of antimicrobial compounds due to their ability to produce a large variety of bioactive compounds and the observation that virtually every fungus may still contain yet unknown so called “cryptic,” often silenced, compounds. These putative metabolites could include novel bioactive compounds. Considerable effort is spent on methods to induce production of these “cryptic” metabolites. One approach is the use of small molecule effectors, potentially influencing chromatin landscape in fungi. We observed that the supernatant of the fungus Doratomyces (D.) microsporus treated with valproic acid (VPA) displayed antimicrobial activity against Staphylococcus (S.) aureus and two methicillin resistant clinical S. aureus isolates. VPA treatment resulted in enhanced production of seven antimicrobial compounds: cyclo-(L-proline-L-methionine) (cPM), p-hydroxybenzaldehyde, cyclo-(phenylalanine-proline) (cFP), indole-3-carboxylic acid, phenylacetic acid (PAA) and indole-3-acetic acid. The production of the antimicrobial compound phenyllactic acid was exclusively detectable after VPA treatment. Furthermore three compounds, cPM, cFP, and PAA, were able to boost the antimicrobial activity of other antimicrobial compounds. cPM, for the first time isolated from fungi, and to a lesser extent PAA, are even able to decrease the minimal inhibitory concentration of ampicillin in MRSA strains. In conclusion we could show in this study that VPA treatment is a potent tool for induction of “cryptic” antimicrobial compound production in fungi, and that the induced compounds are not exclusively linked to the secondary metabolism. Furthermore this is the first discovery of the rare diketopiperazine cPM in fungi. Additionally we could demonstrate that cPM and PAA boost antibiotic activity against antibiotic resistant strains, suggesting a possible application in combinatorial antibiotic treatment against resistant pathogens.