Redefining Humicola sensu stricto and related genera in the Chaetomiaceae

Abstract

The traditional concept of the genus Humicola includes species that produce pigmented, thick-walled and single-celled spores laterally or terminally on hyphae or minimally differentiated conidiophores. More than 50 species have been described in the genus. Species commonly occur in soil, indoor environments, and compost habitats. The taxonomy of Humicola and morphologically similar genera is poorly understood in modern terms. Based on a four-locus phylogeny, the morphological concept of Humicola proved to be polyphyletic. The type of Humicola, H. fuscoatra, belongs to the Chaetomiaceae. In the Chaetomiaceae, species producing humicola-like thick-walled spores are distributed among four lineages: Humicola sensu stricto, Mycothermus, Staphylotrichum, and Trichocladium. In our revised concept of Humicola, asexual and sexually reproducing species both occur. The re-defined Humicola contains 24 species (seven new and thirteen new combinations), which are described and illustrated in this study. The species in this genus produce conidia that are lateral, intercalary or terminal on/in hyphae, and conidiophores are not formed or are minimally developed (micronematous). The ascospores of sexual Humicola species are limoniform to quadrangular in face view and bilaterally flattened with one apical germ pore. Seven species are accepted in Staphylotrichum (four new species, one new combination). Thick-walled conidia of Staphylotrichum species usually arise either from hyphae (micronematous) or from apically branched, seta-like conidiophores (macronematous). The sexual morph represented by Staphylotrichum longicolleum (= Chaetomium longicolleum) produces ascomata with long necks composed of a fused basal part of the terminal hairs, and ascospores that are broad limoniform to nearly globose, bilaterally flattened, with an apical germ pore. The Trichocladium lineage has a high morphological diversity in both asexual and sexual structures. Phylogenetic analysis revealed four subclades in this lineage. However, these subclades are genetically closely related, and no distinctive phenotypic characters are linked to any of them. Fourteen species are accepted in Trichocladium, including one new species, twelve new combinations. The type species of Gilmaniella, G. humicola, belongs to the polyphyletic family Lasiosphaeriaceae (Sordariales), but G. macrospora phylogenetically belongs to Trichocladium. The thermophilic genus Mycothermus and the type species My. thermophilum are validated, and one new Mycothermus species is described. Phylogenetic analyses show that Remersonia, another thermophilic genus, is sister to Mycothermus and two species are known, including one new species. Thermomyces verrucosus produces humicola-like conidia and is transferred to Botryotrichum based on phylogenetic affinities. This study is a first attempt to establish an inclusive modern classification of Humicola and humicola-like genera of the Chaetomiaceae. More research is needed to determine the phylogenetic relationships of “humicola”-like species outsid...

Gut mycobiome of primary sclerosing cholangitis patients is characterised by an increase of Trichocladium griseum and Candida species

“…This analysis revealed increased levels of the genera Candida and Humicola (species level annotation suggests H. grisea) in PSC patients with and without concomitant colitis compared with HC (all q BH <0.05; figure 1E and F) and UC (all q BH <0.1; figure 1E) individuals. H. grisea, recently reclassified as Trichocladium griseum, 7 belongs to the fungal class Sordariomycetes, thus our results reproduce the significant increase of this class in PSC patients, as previously described by Lemoinne and colleagues, but at increased taxonomic resolution. Previous research on T. griseum showed that it is most frequently isolated from soil and plants but also occasionally found in patients suffering from peritonitis.…”

The Hsp90 Inhibitor, Monorden, Is a Promising Lead Compound for the Development of Novel Fungicides

“…Colonies on PDA after 7 days at 25 • C were mouse gray to pale olivaceous; reverse pink to dull orange at the center and white at the margins (Figure 2B). JS-0112 produced pigmented, thick-walled and single-celled conidia on very short conidiophore along the hyphae, which is one of characteristics of genus Humicola (Wang et al, 2016(Wang et al, , 2019; Figure 2C). FIGURE 2 | Morphological features and phylogenetic tree of JS-0112.…”

“…The genus Humicola, previously known as an asexual genus in the Chaetomiaceae, was recently redefined to produce both asexual and sexual spores (Wang et al, 2019). Most of Humicola species were commonly found in soil, indoor environment, and composts whereas some of them have been known as endophytes (Radhakrishnan et al, 2015;Wang et al, 2016Wang et al, , 2019. Humicola species have displayed potential on the production of antibiotics that are appropriately used in human medicine and agriculture.…”

Re-Evaluation of the Order Sordariales: Delimitation of Lasiosphaeriaceae s. str., and Introduction of the New Families Diplogelasinosporaceae, Naviculisporaceae, and Schizotheciaceae

“…Some families and genera included in our study have been previously reported to be polyphyletic [6,10,11,26,33]. Recently, extensive phylogenetic studies have been performed to properly delimit the family Chaetomiaceae, and its largest genera, Chaetomium and Thielavia [5][6][7]. In the revision of Chaetomium, five new genera (i.e., Amesia, Arcopilus, Collariella, Dichotomopilus, and Ovatospora) were introduced to accommodate species not falling into the monophyletic clade including the type species of the genus, Ch.…”

“…Several studies have been performed on the Chaetomiaceae to properly delimitate the family and their largest genera, i.e., Chaetomium and Thielavia [5][6][7]. As a result, the family currently includes more than 35 genera, of which 17 have been recently introduced to accommodate species previously in Chaetomium and Thielavia, which did not cluster with the type species of these genera.…”