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Polymorphic yeasts can switch between unicellular division and multicellular filamentous growth. Although prevalent in aquatic ecosystems, such as the open ocean, we have a limited understanding of the controlling factors on their morphological variation in an aquatic ecology context. Here we show that substrate concentration regulates cell morphogenesis in a cosmopolitan polymorphic yeast, Aureobasidium pullulans, isolated from the pelagic open ocean and analyzed in liquid batch culture. Filamentous cell development was triggered only under high initial substrate conditions, suggesting that hyphal growth could be more advantageous under eutrophic conditions and may influence pelagic fungal interactions with particulate organic matter. Filamentous growth proportionally declined before the exhaustion of substrate and before budding yeast-type cell division entered stationary phase, possibly modulated by quorum sensing as previously evidenced in other polymorphic yeasts. We also found that budding yeast-type unicells decreased in size and became more elongated in shape in response to substrate depletion, resulting in higher cell surface area to volume ratios, which could affect yeast dispersal and/or provide a nutrient uptake advantage under oligotrophic conditions. Our results demonstrate resource-responsive morphological plasticity in a marine-derived polymorphic yeast, providing mechanistic insight into the ability of fungi to survive fluctuating environmental conditions such as in the open ocean. [ABSTRACT FROM AUTHOR]

Since 2011, we have collected fungi that form synnema-like structures (SSs) bearing many acanthophyses at the apex on water-splashed wood in streams in various regions of Japan. A provisional phylogenetic analysis of strains isolated from SSs based on their nrDNA sequences implied affinity with Physisporinus (Polyporales, Basidiomycota). However, it has not been reported that this genus forms SSs in freshwater habitats. We found a fungus forming not only SSs on the water-boundary part of wood but also resupinate basidiocarps with poroid hymenophores on nonsubmerged parts, and the morphological characteristics of the basidiocarps matched those of Physisporinus. Therefore, we investigated the relationship between SS-forming fungi and their sexual states by taxonomic approaches. Phylogenetic analyses based on nrDNA internal transcribed spacer (ITS) and large subunit (LSU) sequences indicated that SS-forming fungi diverged into five clades in Physisporinus. Each clade was discriminated by the color of SSs, morphology of acanthophyses, and cultural characteristics. Of the five clades, Clade 1, which consisted only of sequences of strains isolated from SSs and basidiocarps produced on rhizomorphs, was closely related to P. eminens and P. undatus, but the morphology of basidiocarps and the manner of basidiocarp development differed. Clade 5 was closely related to P. castanopsidis, P. crocatus, P. pouzarii, P. sanguinolentus, P. subcrocatus, P. tibeticus, and P. vitreus, but the basidiocarp morphology differed. Therefore, Clades 1 and 5 were described as two new species. Regarding Clades 2, 3, and 4, further taxonomic studies with additional specimens are required. SS and acanthophysis formation in wet habitats in streams and in culture could be recognized as new taxonomic and ecological characters of Physisporinus. [ABSTRACT FROM AUTHOR]

Minutisphaera is a recently established genus of freshwater Dothideomycetes characterized by small, globose to subglobose or apothecioid, erumpent to superficial, brown ascomata; fissitunicate, eight-spored, ovoid to obclavate asci; and 1-2- septate, clavate to broadly fusiform, hyaline to pale brown ascospores with or without a gelatinous sheath and filamentous appendages. The genus currently contains two species: M. fimbriatispora, the type species, and M. japonica. The higher-level phylogenetic relationship of Minutisphaera within the Dothideomycetes currently is unresolved. To establish the phylogenetic position of Minutisphaera within the Dothideomycetes and evaluate the phylogenetic affinities of newly collected Minutisphaera-like taxa, we sequenced three rDNA regions--18S, ITS1-5.8SITS2 (ITS) and 28S nuc rDNA, and a protein-coding gene, MCM7, for newly collected strains of Minutisphaera. Based on maximum likelihood and Bayesian analyses of a combined dataset (18S and 28S) composed of 167 taxa, a more refined dataset (28S and MCM7) comprising 52 taxa and a separate ITS dataset, and an examination of morphology, we describe and illustrate two new species of Minutisphaera. The Minutisphaera clade was strongly supported within the Dothideomycetes with likelihood and Bayesian statistics but did not share phylogenetic affinities with any existing taxonomic group within the Dothideomycetes. We therefore establish a new order, Minutisphaerales, and new family, Minutisphaeraceae, for this monophyletic clade of freshwater ascomycetes. Chemical analysis of the organic extract M. aspera (G427) resulted in isolation and characterization of five known secondary metabolites, of which four were dipeptides (1-4) and one an aromatic polyketide (5). Conversely, two aromatic polyketides (5, 6) were isolated and identified from the organic extract of M. parafimbriatispora (G156-4). The isolated compounds were tested for their antimicrobial activity against an array of bacteria and fungi. Compound 6 showed promising activity against Staphylococcus aureus and Mycobacterium smegmatis with minimal inhibitory concentration values of 30 and 60 mg/mL, respectively. [ABSTRACT FROM AUTHOR]

During investigations of freshwater ascomycetes we found one interesting taxon from Aomori (Japan), as well as three additional taxa from North Carolina (USA), which were morphologically similar to Minutisphaera, a recently described freshwater fungus in the Dothideomycetes. The ascomata of all the collections bore dark hair-like structures around the ostiolar region, obovoid to obclavate bitunicate asci, and one to three septate hyaline to brown ascospores with a sheath (in material from Japan), and with both sheath and appendages (in material from the USA). The apothecial ascomata of these taxa, however, differ from those of the type species of the genus, which are perithecial. Two collections of Minutisphaera-like fungi from the USA were morphologically quite similar but differed in ascospore size. To assess the phylogenetic affinities of Minutisphaera-like taxa with the type. species, M. fimbriatispora, we sequenced 18S and 28S nrDNA of five newly collected strains of Minutisphaera. We also sequenced the nrDNA for the entire internal transcribed spacer region of 10 strains to assess interspecific and intraspecific variation with M. fimbriatispora. Additionally we examined the secondary metabolite profiles of two strains from USA. Based on maximum likelihood and Bayesian analyses of combined 18S and 28S, and separate ITS sequences, as well as examination of morphology, we describe and illustrate a new species, M. japonica. One collection from North Carolina is confirmed as M. fimbriatispora, while two other collections are Minutisphaera-like fungi that had a number of similar diagnostic morphological characters but differed only slightly in ascospore sizes. The phylogeny inferred from the internal transcribed spacer region suggested that two out of the three North Carolina collections may be novel and perhaps cryptic species within Minutisphaera. Organic extracts of Minutisphaera from USA, M. fimbriatispora (G155-1) and Minutisphaera-like taxon (G156-1), revealed the presence of palmitic acid and (E)-hexadec-9-en-l-ol as major chemical constituents. We discuss the placement of the Minutisphaera clade within the Dothideomycetes. The description of the genus Minutisphaera is emended to accommodate M. japonica within Minutisphaera. [ABSTRACT FROM AUTHOR]

Three new genera are established in the Sordariomycetidae based on morphological and molecular data (SSU and LSU nrDNA) to accommodate five ascomycete species collected from submerged woody debris in freshwater habitats from Costa Rica. The genus Bullimyces contains three new species, B. communis, B. costaricensis and B. aurisporus. Bullimyces is characterized by globose to subglobose, membranous, black, ostiolate ascomata; deliquescent, hyaline, globose cells that fill the center of the centrum; unitunicate asci that deliquesce early in some species; and septate, thick-walled ascospores with or without gelatinous sheaths or appendages. BuUimyces species form a well supported clade with 100% bootstrap support, but the position of the genus in the Sordariomycetidae remains unclear. The second genus, Riomyces, is represented by a single species, R. rotundus. Riomyces is characterized by globose to subglobose, membranous, black, ostiolate ascomata, unitunicate, cylindrical asci, hyaline, globose cells that fill the hamathecium and septate, thick-walled ascospores with a gelatinous sheath. Although Riomyces is morphologically similar to Bullimyces, the two genera did not group together with support in any analysis. The third genus, Hydromelitis, is represented by a single species, H. pulchella. Hydromelitis is characterized by pyriform, membranous, black, ostiolate ascomata, unitunicate asci lacking an apical structure, simple, thin-walled, septate paraphyses and hyaline to golden yellow, multiseptate, thick-walled ascospores with a gelatinous sheath. Bullimyces, Riomyces and Hydromelitis were nested within an unsupported clade consisting of members of the Ophiostomatales, Magnaporthales and freshwater Annulatacaceae sensu lato and sensu stricto. [ABSTRACT FROM AUTHOR]

A new ascomycete species, Natipusilla bellaspora, collected from submerged woody debris in a freshwater stream at Los Amigos Biological Station, Madre De Dios in the Peruvian Amazon is described and illustrated. This fungus is characterized by small, globose to subglobose, hyaline ascomata; small, globose to subglobose, eight-spored fissitunicate asci; one-septate, multiguttulate ascospores with two different gelatinous sheaths, an outer amorphous sheath that enlarges in water and an inner sheath that has a distinctive persistent shape and is attached to the ascospore apex. Morphologically N. bellaspora differs from other Natipusilla species in having larger ascospores and two ascospore sheaths. A second Natipusilla species, N. limonensis, is reported for the first time from Peru. Based on the unique morphological characters of taxa in Natipusilla and results of previous molecular phylogenetic analyses with other members of the Dothideomycetes, we establish Natipusillaceae fam. nov. for this unique tropical freshwater clade. [ABSTRACT FROM AUTHOR]

Two new genera are established in the Dothideomycetes based on morphological and molecular data (SSU and LSU nuclear ribosomal sequences) to accommodate four ascomycete species collected from woody debris submerged in freshwater habitats. The genus Minutisphaera is represented by a single species, M. fimbriatispora, which was collected from freshwater habitats in temperate forests in North America. It has small, superficial, brown, subglobose, papillate pseudothecia with dark, irregularly twisted hairs around the papillae, fissitunicate asci, septate pseudoparaphyses, and hyaline, one-septate ascospores surrounded by a gelatinous sheath and having spine-like appendages radiating around the ascospore at the septum. Minutisphaera formed a strongly supported clade with Farlowiella carmichaeliana. The second genus, Natipusilla, contains three new species, N. decorospora, N. limonensis and N. naponensis, which were collected from Central and South America. Natipusilla is characterized by small, superficial, light-colored, globose pseudothecia, fissitunicate asci, few or no pseudoparaphyses, and hyaline, one-septate to tardily two- or three-septate ascospores with or without a gelatinous sheath. The three Natipusilla species form a well supported clade, but their relationship to other members of the Dothideomycetes remains unclear. [ABSTRACT FROM AUTHOR]

The teleomorph of Aquaphila albicans was discovered on submerged wood collected in Thailand. Its black, soft-textured, setose ascomata, bitunicate asci and hyaline to pale brown, multiseptate ascospores indicated an affinity to Tubeufiaceae (Dothideomycetes). After morphological or molecular comparisons with related species in Tubeufia, Acanthostigma and Taphrophila, it is described and illustrated as a new species, T. asiana Sivichai & K.M. Tsui, sp. nov. Finding this Tubeufia teleomorph was surprising, given the falcate conidia of its A. albicans anamorph, which superficially resemble the conidia of Fusarium and not the coiled, helicosporous conidia of other species in Tubeufiaceae. We assessed the phylogenetic relationships of A. albicans-T, asiana with ribosomal sequences from SSU and ITS and partial LSU regions by parsimony and Bayesian analysis. An initial set of 40 taxa representing a wide range of ascomycete families and their SSU sequences from GenBank showed A. albicans-T, asiana to be nested within the Tubeufiaceae with 100% bootstrap support. Their placement was inferred with ITS and partial LSU ribosomal sequences. The nearly identical ITS sequences of two isolates of A. albicans and one isolate of Tubeufia asiana united these fungi as a monophyletic group with 100% bootstrap support and further nested them, with 88% bootstrap support, in a clade containing Helicoon gigantisporum and Helicoma chlamydosporum. This is the first molecular phylogenetic study to place a nonhelicosporous species within the Tubeufiaceae and to show that helical conidia were lost at least once within the family. [ABSTRACT FROM AUTHOR]

Three pyrenomycetes collected from woody debris submerged in freshwater habitats are described as new species of Luttrellia: L. guttulata sp. nov., L. halonata sp. nov. and L. parvulospora sp. nov. A collection of L. estuarina, the type species of the genus, having ascospores surrounded by a gelatinous sheath, a characteristic not observed in the type specimen, is reported. The genus description is emended to include fungi with 4- or 8-spored asci and ascospores with or without a gelatinous sheath. Luttrellia is distinguished from other genera in the Halosphaeriaceae by hyaline, phragmoseptate, and thick-walled ascospores with or without a gelatinous sheath. [ABSTRACT FROM AUTHOR]

We observed the sequence of fungi appearing on submerged wood of Hibiscus tiliaceus that initially was either dead or alive. Branches that were dead, but still attached to the tree, and live branches were cut from H. tiliaceus in the riparian vegetation in a brackish habitat on the Tutong River, Brunei. Branch segments were connected to the riverbank using monofilament line. Samples were examined for fungi before the branches were placed in the river and after the branches had been submerged 3 or 6 mo. Fifty taxa were found on the samples. Before being placed in the water different fungal assemblages were found on live as compared to deadwood. Branches that were alive when cut supported a distinctly different fungal assemblage after 3 mo in the water. Dead branches after 3 mo and both dead and initially live samples after 6 mo had been colonized by a fungal assemblage that is typical at this site. It is unknown whether the differences in colonization of dead and initially live wood can be attributed to differences in the substratum (i.e., the presence or absence of bark), inhibitory substances in more recently live wood or to assembly rules resulting from the different fungi that already were present in dead and live branches. [ABSTRACT FROM AUTHOR]