Bradymyces gen. nov. (Chaetothyriales, Trichomeriaceae), a new ascomycete genus accommodating poorly differentiated melanized fungi

Discovery of Formicomyces microglobosus gen. et sp. nov. strengthens the hypothesis of independent evolution of ant-associated fungi in Trichomeriaceae

Different groups of fungi have been reported to interact with ants. Recent studies have shown that fungi of the order Chaetothyriales are important components of ant-fungus networks, including members of the family Trichomeriaceae, which is particularly rich in fungi isolated from carton ants nests. One of the still understudied ant-related environments are ants' infrabuccal pockets and pellets, which often contain fungal matter. The aim of this work was to determine the systematic and phylogenetic position of two slow growing strains of Trichomeriaceae isolated from infrabuccal pellets of Formica polyctena ants. Molecular analyses based on maximum likelihood and bayesian inference, using sequences of two ribosomal DNA markers: ITS and LSU have shown that the isolated strains form a monophyletic clade within the family Trichomeriaceae, sister to a clade formed by representatives of the genus Trichomerium. Morphological analyses additionally justified distinctiveness of the isolated strains, which have different morphology of conidia and conidiophores than Trichomerium representatives. Therefore, our results show that the isolated strains represent a new species within a not yet described fungal genus. Due to the strains' isolation source and their close relatedness to a fungal strain isolated from a carton nest of Lasius fuliginosus, we propose a name Formicomyces microglobosus Siedlecki & Piątek for this fungus. While our discovery strengthens a hypothesis of the multiple, independent evolution of ant-associated fungi in the family Trichomeriaceae, the ecology of F. microglobosus still remains to be characterized.

A visceral mycosis in farmed rainbow trout (Oncorhynchus mykiss) caused by Neopyrenochaeta submersa

A mycotic infection manifesting as abdominal distension with free serous fluid accumulation in the coelomic cavity is documented in farmed rainbow trout. Histological examination using PAS and silver staining revealed the presence of numerous fungal hyphae in the spleen and gastrointestinal wall. The isolated fungus was sterile and identified by using phylogenetic analysis based on four loci as Neopyrenochaeta submersa. This is the first time this fungus has been reported as pathogen.

Exploring diversity rock-inhabiting fungi from northern Thailand: a new genus and three new species belonged to the family Herpotrichiellaceae

Members of the family Herpotrichiellaceae are distributed worldwide and can be found in various habitats including on insects, plants, rocks, and in the soil. They are also known to be opportunistic human pathogens. In this study, 12 strains of rock-inhabiting fungi that belong to Herpotrichiellaceae were isolated from rock samples collected from forests located in Lamphun and Sukhothai provinces of northern Thailand during the period from 2021 to 2022. On the basis of the morphological characteristics, growth temperature, and multi-gene phylogenetic analyses of a combination of the internal transcribed spacer, the large subunit, and the small subunit of ribosomal RNA, beta tubulin and the translation elongation factor 1-a genes, the new genus, Petriomyces gen. nov., has been established to accommodate the single species, Pe. obovoidisporus sp. nov. In addition, three new species of Cladophialophora have also been introduced, namely, Cl. rupestricola, Cl. sribuabanensis, and Cl. thailandensis. Descriptions, illustrations, and a phylogenetic trees indicating the placement of these new taxa are provided. Here, we provide updates and discussions on the phylogenetic placement of other fungal genera within Herpotrichiellaceae.

Microbial gradual shifts during the process of species replacement in Taihang Mountain

Introduction

Understanding microbial gradual shifts along species replacement can help elucidate the mechanisms driving secondary succession, and predict microbial responses to changing environments. However, how climate-induced species replacement alters microbial processes, and whether microbial shifts follow predictable assembly trajectories remain unclear.

Methods

Using space-for-time substitution approach, we studied shifts in bacterial and fungal communities in the succession from Leptodermis oblonga to Vitex negundo var. heterophylla shrubland in Taihang Mountain.

Results and Discussion

Species replacement, induced by climate related environmental change, significantly increased the above-ground biomass of shrublands, and TP and TK contents in topsoil. The succession from L. oblonga to V. negundo var. heterophylla communities resulted in the gradually replacement of cold-tolerant microbes with warm-affinity ones, and alterations of microbial communities involved in soil biogeochemical processes. Soil and plant variables, such as above-ground biomass, soil pH, total phosphorus, and total potassium, well explained the variations in microbial communities, indicating that the coordinated changes in plant communities and soil properties during secondary succession caused accompanied shifts in microbial diversity and composition.

Knufia obscura sp. nov. and Knufia victoriae sp. nov., two new species from extreme environments

Six strains of black meristematic fungi were isolated from Antarctic soils, gasoline car tanks and from the marine alga Flabellia petiolata. These fungi were characterized by morphological, physiological and phylogenetic analyses. According to the maximum-likelihood analysis reconstructed with ITS and LSU sequences, these strains belonged to the genus Knufia. Knufia obscura sp. nov. (holotype CBS 148926) and Knufia victoriae sp. nov. (holotype CBS 149015) are proposed as two novel species and descriptions of their morphological, physiological and phylogenetic features are presented. Based on the maximum-likelihood analyses, K. obscura was closely related to Knufia hypolithi (99 % bootstrap support), while K. victoriae clustered in the clade of Knufia cryptophialidica and Knufia perfecta (93 % bootstrap support). Knufia victoriae, recorded in Antarctic soil samples, had a psychrophilic behaviour, with optimal growth between 10 and 15 °C and no growth recorded at 20 °C. Knufia obscura, from a gasoline car tank and algae, displayed optimal growth between 20 and 25 °C and was more tolerant to salinity than K. victoriae.

Rock-inhabiting fungi: terminology, diversity, evolution and adaptation mechanisms

Rock-inhabiting fungi (RIF) constitute an ecological group associated with terrestrial rocks. This association is generally restricted to the persistent colonisation of rocks and peculiar morphological features based on melanisation and slow growth, which endow RIF with significance in eukaryotic biology, special status in ecology, and exotic potential in biotechnology. There is a need to achieve a better understanding of the hidden biodiversity, antistress biology, origin and convergent evolution of RIF, which will facilitate cultural relic preservation, exploitation of the biogeochemical cycle of rock elements and biotechnology applications. This review focuses on summarising the current knowledge of rock-inhabiting fungi, with particular reference to terminology, biodiversity and geographic distribution, origin and evolution, and stress adaptation mechanisms. We especially teased out the definition through summing up the terms related to rock-inhabting fungi, and also provided a checklist of rock-inhabiting fungal taxa recorded following updated classification schemes.

Slow-growing fungi belonging to the unnamed lineage in Chaetothyriomycetidae form hyphal coils in vital ericaceous rhizodermal cells in vitro

The diversity and functionality of ericoid mycorrhizal (ErM) fungi are still being understudied. Members of Chaetothyriomycetidae evolved a specific lifestyle of inhabiting extreme, poor, or toxic environments. Some taxa in this subclass, especially in Chaetothyriales, are also putative ErM taxa, but their mycorrhizal ability is mostly unknown because the members are generally hard to isolate from roots. This study herein focused on eight root isolates and provided their phylogeny and morphology of root colonization. Phylogenetic analysis based on rRNA sequences clarified that the isolated strains were not classified into Chaetothyriales, but in an unnamed lineage in Chaetothyriomycetidae. This lineage also contains rock isolates, bryosymbionts, and a resinicolous species as well as various environmental sequences obtained from soil/root samples. All strains grew extremely slow by mycelia on cornmeal or malt extract agar (2.9-8.5 mm/month) and formed hyphal coils in vital rhizodermal cells of sterile blueberry seedlings in vitro. This study illustrated the presence of a novel putative ErM lineage in Chaetothyriomycetidae.

Sooty molds from the Jurassic of Patagonia, Argentina

PREMISE

The sooty molds are a globally distributed ecological group of ascomycetes with epiphyllous, saprotrophic habit, comprising several phylogenetically distant taxa (i.e., members of the classes Dothideomycetes and Eurotiomycetes). Their fossil record extends almost continuously back to the early Cretaceous; however, they are hypothesized to have originated in the early Mesozoic. Here, we describe new specimens of sooty molds associated with conifer leaves from Jurassic hot spring deposits of Patagonia, Argentina.

METHODS

Thin sections of chert samples from the La Matilde Formation, Deseado Massif (Santa Cruz, Argentina) were observed using light microscopy.

RESULTS

The fungi occur on the surface and axils of leafy twigs with podocarpaceous affinities, forming dense subicula comprised by opaque moniliform hyphae. Additionally, several asexual and sexual reproductive structures are observed. On the basis of vegetative (i.e., dense subicula composed of moniliform hyphae; hyphae composed of opaque cells deeply constricted at the septa) and reproductive characters (i.e., poroconidial and sympodioconidial asexual stages and diverse spores), two morphotypes were identified with affinities within lineages of the subphylum Pezizomycotina that encompass the ecological group of sooty molds, and a third morphotype was within the phylum Ascomycota.

CONCLUSIONS

This finding extends the fossil record of sooty molds to the Jurassic and their geographic fossil range to the South American continent. In particular, their association with podocarpaceous conifers is shown to be ancient, dating back to the Jurassic. This new record provides an additional reference point on the diversity of interactions that characterized Jurassic forests in Patagonia.

Formation of filamentous fungal pellets in aerobic granular sludge via reducing temperature and dissolved oxygen: Characteristics of filamentous fungi and denitrification performance

A lab-scale sequencing batch reactor (SBR) using glucose as carbon source was operated for 500 days to investigate the formation of filamentous organisms and their function on stability of AGS system. After 250 days' stable operation under conditions of 25 ± 2 °C and dissolved oxygen (DO) of 4-5 mg/L (stage I), the temperature and DO were reduced to 10 ± 2 °C and DO of 1-2 mg/L until 280 days (stage II), to induce the growth of filamentous microorganisms. After that until 500 days (stage III), overgrowth of filamentous microorganisms with relative abundances of up to 19.46%, formation of black filamentous fungal pellets, and reconstruction of AGS granules were observed in turn. The relation between settling of AGS (SVI 30-72 mL/g) and filamentous microorganisms was revealed. Filamentous pellets were purified and identified as fungal Bradymyces and Knufia, with stronger denitrification performance on nitrite than nitrate. The results indicated that filamentous fungal pellets contributed to good sludge settling performance and promoted the denitrification process in AGS.

Novel black yeast-like species in chaetothyriales with ant-associated life styles

Among ancestral fungi in Chaetothyriales, several groups have a life style in association with tropical ants, either in domatia or in carton-nests. In the present study, two strains collected from ant carton in Thailand and Malaysia were found to represent hitherto undescribed species. Morphological, physiological, phylogenetic data and basic genome information are provided for their classification. Because of the relatively large phylogenetic distances with known species confirmed by overall genome data, large subunit (LSU) and Internal Transcribed Spacer (ITS) ribosomal DNA sequences were sufficient for taxonomic circumscription of the species. The analyzed strains clustered with high statistical support as a clade in the family Trichomeriaceae. Morphologically they were rather similar, lacking sporulation in vitro. In conclusion, Incumbomyces delicatus and Incumbomyces lentus were described as new species based on morphological, physiological and phylogenetic analysis.

Unveiling the Hidden Diversity of Rock-Inhabiting Fungi: Chaetothyriales from China

Rock-inhabiting fungi (RIF) are nonlichenized fungi that naturally colonize rock surfaces and subsurfaces. The extremely slow growth rate and lack of distinguishing morphological characteristics of RIF resulted in a poor understanding on their biodiversity. In this study, we surveyed RIF colonizing historical stone monuments and natural rock formations from throughout China. Among over 1000 isolates, after preliminary delimitation using the internal transcribed spacer region (ITS) sequences, representative isolates belonging to Trichomeriaceae and Herpotrichiellaceae were selected for a combined analysis of ITS and the nuclear ribosomal large subunit (nucLSU) to determine the generic placements. Eight clades representing seven known genera and one new genus herein named as Anthracina were placed in Trichomeriaceae. While, for Herpotrichiellaceae, two clades corresponded to two genera: Cladophialophora and Exophiala. Fine-scale phylogenetic analyses using combined sequences of the partial actin gene (ACT), ITS, mitochondrial small subunit ribosomal DNA (mtSSU), nucLSU, the largest subunit of RNA polymerase II (RPB1), small subunit of nuclear ribosomal RNA gene (SSU), translation elongation factor (TEF), and β-tubulin gene (TUB) revealed that these strains represented 11 and 6 new species, respectively, in Trichomeriaceae and Herpotrichiellaceae. The 17 new species were described, illustrated for their morphologies and compared with similar taxa. Our study demonstrated that the diversity of RIF is surprisingly high and still poorly understood. In addition, a rapid strategy for classifying RIF was proposed to determine the generic and familial placements through preliminary ITS and nucLSU analyses, followed by combined analyses of five loci selected from ACT, ITS, mtSSU, nucLSU, RPB1, and/or the second subunit of RNA polymerase II gene (RPB2), SSU, TEF, and TUB regions to classify RIF to the species level.

A re-evaluation of the Chaetothyriales using criteria of comparative biology

Chaetothyriales is an ascomycetous order within Eurotiomycetes. The order is particularly known through the black yeasts and filamentous relatives that cause opportunistic infections in humans. All species in the order are consistently melanized. Ecology and habitats of species are highly diverse, and often rather extreme in terms of exposition and toxicity. Families are defined on the basis of evolutionary history, which is reconstructed by time of divergence and concepts of comparative biology using stochastical character mapping and a multi-rate Brownian motion model to reconstruct ecological ancestral character states. Ancestry is hypothesized to be with a rock-inhabiting life style. Ecological disparity increased significantly in late Jurassic, probably due to expansion of cytochromes followed by colonization of vacant ecospaces. Dramatic diversification took place subsequently, but at a low level of innovation resulting in strong niche conservatism for extant taxa. Families are ecologically different in degrees of specialization. One of the clades has adapted ant domatia, which are rich in hydrocarbons. In derived families, similar processes have enabled survival in domesticated environments rich in creosote and toxic hydrocarbons, and this ability might also explain the pronounced infectious ability of vertebrate hosts observed in these families. Conventional systems of morphological classification poorly correspond with recent phylogenetic data. Species are hypothesized to have low competitive ability against neighboring microbes, which interferes with their laboratory isolation on routine media. The dataset is unbalanced in that a large part of the extant biodiversity has not been analyzed by molecular methods, novel taxonomic entities being introduced at a regular pace. Our study comprises all available species sequenced to date for LSU and ITS, and a nomenclatural overview is provided. A limited number of species could not be assigned to any extant family.

Clinical and histopathological changes in rainbow trout Oncorhynchus mykiss experimentally infected with fungus Bradymyces oncorhynchi

Bradymyces oncorhynchi is a poorly known melanised fungal species that has been isolated only from a hyperaemic focus near the enlarged spleen of a rainbow trout. Although the pathogenicity of this species to fish is suspected, it has not been fully confirmed. Four laboratory experiments were conducted to test the effect of the fungus on the health of rainbow trout fingerlings. Mycelia were cultivated under different conditions to increase inoculum variability and to test the impact of the conditions on the pathogenicity. The inoculum was subsequently administered by the intraperitoneal route. The clinical manifestations, gross pathological lesions and histopathological changes were identical in all experimental groups, i.e. lethargy, inappetence, anorexia, weight reduction, pale gills, full-thickness ulceration of the abdominal wall, muscle atrophy, haemorrhagic or pale liver, fat-altered pyloric region with haemorrhages, enlarged spleen, haemorrhagic ascites, systemic granulomatous lesions with the presence of melanised hyphae (phaeohyphomycosis), multifocal granulomatous hepatitis, perivascular lymphocytic infiltration, vacuolation of hepatocytes and vacuolation of the kidney tubule epithelium. No statistically significant differences were found in the survival of the fish with respect to experimental settings. The survival period ranged between 3 and 135 days.

Swim bladder mycosis in farmed rainbow trout Oncorhynchus mykiss caused by Phoma herbarum and experimental verification of pathogenicity

In this study, spontaneous swim bladder mycosis was documented in a farmed fingerling rainbow trout from a raceway culture system. At necropsy, the gross lesions included a thickened swim bladder wall, and the posterior portion of the swim bladder was enlarged due to massive hyperplasia of muscle. A microscopic wet mount examination of the swim bladder contents revealed abundant septate hyphae, and histopathological examination showed periodic acid-Schiff-positive mycelia in the lumen and wall of the swim bladder. Histopathological examination of the thickened posterior swim bladder revealed muscle hyperplasia with expansion by inflammatory cells. The causative agent was identified as Phoma herbarum through morphological analysis and DNA sequencing. The disease was reproduced in rainbow trout fingerlings using intraperitoneal injection of a spore suspension. Necropsy in dead and moribund fish revealed extensive congestion and haemorrhages in the serosa of visceral organs and in liver and abdominal serosanguinous fluid. Histopathological examination showed severe hepatic congestion, sinusoidal dilatation, Kupffer cell reactivity, leukostasis and degenerative changes. Fungi were disseminated to the liver, pyloric caeca, kidney, spleen and heart. Although infections caused by Phoma spp. have been repeatedly reported in fish, species identification has been hampered by extensive taxonomic changes. The results of this study confirmed the pathogenicity of P. herbarum in salmonids by using a reliably identified strain during experimental fish infection and provides new knowledge regarding the course of infection.

Aquatic urban ecology at the scale of a capital: community structure and interactions in street gutters

In most cities, streets are designed for collecting and transporting dirt, litter, debris, storm water and other wastes as a municipal sanitation system. Microbial mats can develop on street surfaces and form microbial communities that have never been described. Here, we performed the first molecular inventory of the street gutter-associated eukaryotes across the entire French capital of Paris and the non-potable waters sources. We found that the 5782 OTUs (operational taxonomic units) present in the street gutters which are dominated by diatoms (photoautotrophs), fungi (heterotrophs), Alveolata and Rhizaria, includes parasites, consumers of phototrophs and epibionts that may regulate the dynamics of gutter mat microbial communities. Network analyses demonstrated that street microbiome present many species restricted to gutters, and an overlapping composition between the water sources used for street cleaning (for example, intra-urban aquatic networks and the associated rivers) and the gutters. We propose that street gutters, which can cover a significant surface area of cities worldwide, potentially have important ecological roles in the remediation of pollutants or downstream wastewater treatments, might also be a niche for growth and dissemination of putative parasite and pathogens.

Disseminated infection due to Exophiala pisciphila in Cardinal tetra, Paracheirodon axelrodi

Cardinal tetra, Paracheirodon axelrodi (Schultz, 1956), kept in an ornamental tank, was found to be affected by severe invasive mycosis. Externally, the disease manifested as abdominal swelling, and internally, the anterior part of the intestine was extremely bloated with abundant dematiaceous septate hyphae and an accumulation of fluid. Histopathologically, a granulomatous inflammatory response was observed in the intestine wall, kidney and spleen. We assume that the mycotic agent was primarily deposited in the intestine and was then gradually disseminated to the other organs. DNA sequencing of ITS and LSU rDNA regions and phenotypic characterization were used for identification of the isolated fungus. The obtained data confirmed that the infection was caused by Exophiala pisciphila. The disease was subsequently reproduced in the carp fingerling using intramuscular and intraperitoneal injection of a spore suspension. The 13th day after intramuscular infection, a marked elevation of neutrophils was recorded in the peripheral blood; this involved a proliferation of band forms and segmented forms. As far as we know, this is the first report of infection due to E. pisciphila in Cardinal tetra.

Cephalotheca sulfurea (Ascomycota, Sordariomycetes), a new fungal pathogen of the farmed rainbow trout Oncorhynchus mykiss

The first case of visceral mycotic infection due to Cephalotheca sulfurea (Cephalothecaceae, Ascomycota) is documented in farmed rainbow trout from a raceway culture system. The disease clinically manifested as a hyperaemic area in the liver of the fish, and histological examination using silver and PAS staining showed the presence of numerous foci of hyphae and spores. The causative agent was first isolated in pure culture from the liver and identified using morphological characteristics. Sequence data from ITS and LSU rDNA also clearly confirmed C. sulfurea as the causal agent. The pathogenicity of related species belonging to the family Cephalothecaceae has been well-documented in humans and dogs (superficial as well as systemic infections). However, C. sulfurea has never been reported as a pathogen of humans or animals, including marine and freshwater fishes. The morphological identification of C. sulfurea is difficult due to its similarity to several different fungal genera, and molecular methods are strongly recommended for reliable identification.

From the Tunnels into the Treetops: New Lineages of Black Yeasts from Biofilm in the Stockholm Metro System and Their Relatives among Ant-Associated Fungi in the Chaetothyriales

Rock-inhabiting fungi harbour species-rich, poorly differentiated, extremophilic taxa of polyphyletic origin. Their closest relatives are often well-known species from various biotopes with significant pathogenic potential. Speleothems represent a unique rock-dwelling habitat, whose mycobiota are largely unexplored. Isolation of fungi from speleothem biofilm covering bare granite walls in the Kungsträdgården metro station in Stockholm yielded axenic cultures of two distinct black yeast morphotypes. Phylogenetic analyses of DNA sequences from six nuclear loci, ITS, nuc18S and nuc28S rDNA, rpb1, rpb2 and β-tubulin, support their placement in the Chaetothyriales (Ascomycota). They are described as a new genus Bacillicladium with the type species B. lobatum, and a new species Bradymyces graniticola. Bacillicladium is distantly related to the known five chaetothyrialean families and is unique in the Chaetothyriales by variable morphology showing hyphal, meristematic and yeast-like growth in vitro. The nearest relatives of Bacillicladium are recruited among fungi isolated from cardboard-like construction material produced by arboricolous non-attine ants. Their sister relationship is weakly supported by the Maximum likelihood analysis, but strongly supported by Bayesian inference. The genus Bradymyces is placed amidst members of the Trichomeriaceae and is ecologically undefined; it includes an opportunistic animal pathogen while two other species inhabit rock surfaces. ITS rDNA sequences of three species accepted in Bradymyces and other undescribed species and environmental samples were subjected to phylogenetic analysis and in-depth comparative analysis of ITS1 and ITS2 secondary structures in order to study their intraspecific variability. Compensatory base change criterion in the ITS2 secondary structure supported delimitation of species in Bradymyces, which manifest a limited number of phenotypic features useful for species recognition. The role of fungi in the speleothem biofilm and relationships of Bacillicladium and Bradymyces with other members of the Chaetothyriales are discussed.

Arthrocladium, an unexpected human opportunist in Trichomeriaceae (Chaetothyriales)

The family Trichomeriaceae (Chaetothyriales) mainly comprises epiphytic and epilithic organisms. In some species elaborate ascomata are formed, but for the great majority the species no asexual conidium formation is known other than simple fragmentation of the thallus. The present paper re-establishes the genus Arthrocladium with three non-sporulating species. One of these is described for a strain causing a fatal infection in a human patient with a rare genetic immune disorder.

Backbone tree for Chaetothyriales with four new species of Minimelanolocus from aquatic habitats

We are studying the freshwater lignicolous fungi along a north-south latitudinal gradient in Asia. In this paper, fresh collections of Minimelanolocus from submerged wood in streams in Yunnan Province, China are characterised based on morphology and molecular phylogeny based on three rDNA regions: 18S (SSU), ITS1-5.8S-ITS2 (ITS) and 28S nuclear rDNA (LSU). The phylogenetic analysis of combined LSU and SSU sequence data and a separate analysis of ITS placed the isolates within the family Herpotrichiellaceae, order Chaetothyriales. An updated phylogenetic backbone tree for Chaetothyriales is provided with available ex-type and additional isolates. One of the isolates collected was identified as Minimelanolocus obscurus based on morphology and molecular data. Minimelanolocus aquaticus, M. asiaticus, M. curvatus and M. melanicus are described as new species considering the interspecific ITS variability and morphology. The phylogenetic placement of Minimelanolocus in Chaetothyriales is novel and provides new sequence data for the genus as a distinct lineage in Chaetothyriales. The conidial characters of all the known species in the genus are summarized. Descriptions and illustrations are provided for the five species of Minimelanolocus with notes on their taxonomy and phylogeny.