M. L. Georgieva

On the diversity of fungi from soda soils

The diversity of filamentous fungi that can grow at high ambient pH values (i.e., 8–11) remains largely understudied. Here we study 100 alkalitolerant and alkaliphilic isolates from the soils around the basin of soda lakes in Asia and Africa to assess the major evolutionary lineages and morphologies pertinent to the alkaliphilic trait in filamentous fungi. The Emericellopsis lineage (Hypocreales, Hypocreomycetidae), along with Plectosphaerellaceae (Hypocreomycetidae), Pleosporaceae (Dothideomycetes), Chaetomiaceae (Sordariomycetidae) families appeared to be overrepresented with strong alkalitolerants and effective alkaliphiles. In particular, Sodiomyces species (Plectosphaerellaceae), Acrostalagmus luteoalbus (Plectosphaerellaceae), Emericellopsis alkalina (Hypocreales), Thielavia sp. (Chaetomiaceae), and Alternaria sect. Soda (Pleosporaceae) grew best at high ambient pH. The pH tolerance of Chordomyces antarcticum, Acrostalagmus luteoalbus and some other species was largely affected by the presence of extra Na+ in the growth medium. Moderate alkalitolerants included Scopulariopsis members (Microascales), Fusarium, Cladosporium, and many asexual acremonium-like species from Bionectriaceae. Weak alkalitolerants were represented by sporadic isolates of Penicillium, Purpureocillium lilacinum, and Alternaria alternata species, with the growth optimum at neutral or acidic pH. Weak alkalitolerants develop loose dry chains of spores easily dispersed by air. Their presence at low frequency with the growth optimum at neutral or acidic pH leads us to treat them as transient species in the alkaline soils, as those are also ubiquitous saprobes in normal soils. Our phylogenetic analyses show that the alkaliphilic trait in filamentous fungi has evolved several times. Several lineages harboring strong alkalitolerants derived from the known marine-borne fungi (Emericellopsis, Alternaria sect. Phragmosporae), or fall within the fungi associated with halophytic grasses (Pleosporaceae). Soda soils contain a diversity of fungi that range from weak alkalitolerant to alkaliphilic, which in few cases is associated with darkly pigmented mycelium and formation of microsclerotia. The alkaliphilic trait is spread throughout the Ascomycota, and usually juxtaposes with slime-covered polyphyletic acremonium-, verticillium-, gliocladium-types of asexual morphology, hyphae aggregating in chords, and enclosed fruit bodies.

Sodiomyces alkalinus, a new holomorphic alkaliphilic ascomycete within the Plectosphaerellaceae.

In this study we reassess the taxonomic reference of the previously described holomorphic alkaliphilic fungus Heleococcum alkalinum isolated from soda soils in Russia, Mongolia and Tanzania. We show that it is not an actual member of the genus Heleococcum (order Hypocreales) as stated before and should, therefore, be excluded from it and renamed. Multi-locus gene phylogeny analyses (based on nuclear ITS, 5.8S rDNA, 28S rDNA, 18S rDNA, RPB2 and TEF1-alpha) have displayed this fungus as a new taxon at the genus level within the family Plectosphaerellaceae, Hypocreomycetidae, Ascomycota. The reference species of actual Heleococcum members showed clear divergence from the strongly supported Heleococcum alkalinum position within the Plectosphaerellaceae, sister to the family Glomerellaceae. Eighteen strains isolated from soda lakes around the world show remarkable genetic similarity promoting speculations on their possible evolution in harsh alkaline environments. We established the pH growth optimum of this alkaliphilic fungus at c. pH 10 and tested growth on 30 carbon sources at pH 7 and 10. The new genus and species, Sodiomyces alkalinus gen. nov. comb. nov., is the second holomorphic fungus known within the family, the first one being Plectosphaerella – some members of this genus are known to be alkalitolerant. We propose the Plectosphaerellaceae family to be the source of alkaliphilic filamentous fungi as also the species known as Acremonium alcalophilum belongs to this group.

Are alkalitolerant fungi of the Emericellopsis lineage (Bionectriaceae) of marine origin

Surveying the fungi of alkaline soils in Siberia, Trans-Baikal regions (Russia), the Aral lake (Kazakhstan), and Eastern Mongolia, we report an abundance of alkalitolerant species representing the Emericellopsis-clade within the Acremonium cluster of fungi (order Hypocreales). On an alkaline medium (pH ca. 10), 34 acremonium-like fungal strains were obtained. One of these was able to develop a sexual morph and was shown to be a new member of the genus Emericellopsis, described here as E. alkalina sp. nov. Previous studies showed two distinct ecological clades within Emericellopsis, one consisting of terrestrial isolates and one predominantly marine. Remarkably, all the isolates from our study sites show high phylogenetic similarity based on six loci (LSU and SSU rDNA, RPB2, TEF1-α, β-tub and ITS region), regardless of their provenance within a broad geographical distribution. They group within the known marine-origin species, a finding that provides a possible link to the evolution of the alkaliphilic trait in the Emericellopsis lineage. We tested the capacities of all newly isolated strains, and the few available reference ex-type cultures, to grow over wide pH ranges. The growth performance varied among the tested isolates, which showed differences in growth rate as well as in pH preference. Whereas every newly isolated strain from soda soils was extremely alkalitolerant and displayed the ability to grow over a wide range of ambient pH (range 4–11.2), reference marine-borne and terrestrial strains showed moderate and no alkalitolerance, respectively. The growth pattern of the alkalitolerant Emericellopsis isolates was unlike that of the recently described and taxonomically unrelated alkaliphilic Sodiomyces alkalinus, obtained from the same type of soils but which showed a narrower preference towards high pH.

Mycelial fungi in saline soils of the western Transbaikal region

Mycelial fungi in a solonchakous chestnut soil, a sulfate solonchak, and a soda solonchak were studied in the western Lake Baikal basin. The humus content, the degree of salinization, and the composition of salts affected the structure of the micromycete communities. In the chestnut soil, more than half of the species identified were found. The species diversity was higher in the nonsaline and humus horizons. The eolian deposit on the soda solonchak was characterized by the presence of six species of fungi that did not occur in other soil horizons. Their occurrence in the fresh deposit seems to be related to the eolian transfer of fungi with the fine earth from the adjacent areas with the nonsaline soils. The soda solonchak fungi are dominated by the haloalkalitolerant and alkalophilic micromycetes, among which the representatives of the Acremonium (A. antarcticum and A. rutilum) and Verticillum genera and Mycelia sterilia were identified. There was also an alkalophilic ascomycete, which is an indicator of soda salinization—Heleococcum alkalinum. On the whole, the soda solonchak had the lowest number of fungal germs and the lowest species diversity of mycelial fungi among the soils compared.

Alkalitolerant micromycetes in acidic and neutral soils of the temperate zone

A wide diversity of micromycetes from various taxonomic groups in acidic and neutral soils is known from the literature data. In the present work, the fungi isolated from these soils and capable of growth at high pH are analyzed. The fungi were isolated from acidic sod-podzol and neutral cultivated soils by plating on alkaline agar (pH 10.0–10.5). Their identification was carried out using morphological, cultural, and molecular genetic criteria. Phylogenetic analysis was performed and the rates of linear growth within a broad pH range (4.0–10.4) were determined. The isolates represented a polyphyletic group of ascomycetes (Sordariomycetes), which included members of Plectosphaerellaceae (5 species) and various families of Hypocreales (4 species). The most common species were Gibellulopsis nigrescens, Acrostalagmus luteoalbus, Chordomyces antarcticum, and Plectosphaerella spp. Investigation of fungal growth at different pH values revealed all isolates to be alkalitolerant, with no alkaliphilic fungi isolated from acidic sod-podzol and neutral cultivated soils. Although the group of isolates was polyphyletic and its members originated from different ecological and trophic niches, most alkalitolerant isolates exhibited common morphological traits with acremonium- and verticillium-like conidial spore formation, abundant slime formation, and a tendency for aggregation of their mycelium in bundles. Our research confirmed the presence of fungi with alkalitolerant adaptation to external pH in the sod-podzolic and cultivated soils of the Moscow region.

Dynamics of the cytosol soluble carbohydrates and membrane lipids in response to ambient pH in alkaliphilic and alkalitolerant fungi

Comparative composition of lipids and cytosol soluble carbohydrates at different ambient pH values was studied for two obligately alkaliphilic fungi (Sodiomyces magadii and S. alkalinus) and for two alkalitolerant ones (Acrostalagmus luteoalbus and Chordomyces antarcticus). The differences and common patterns were revealed in responses to pH stress for the fungi with different types of adaptation to ambient pH. While trehalose was one of the major cytosol carbohydrates in alkaliphilic fungi under optimal growth conditions (pH 10.2), pH decrease to 7.0 resulted in doubling its content. In alkalitolerant fungi trehalose was a minor component and its level did not change significantly at different pH. In alkalitolerant fungi, arabitol and mannitol were the major carbohydrate components, with their highest ratio observed under alkaline conditions and the lowest one, under neutral and acidic conditions. In alkaliphiles, significant levels of arabitol were revealed only under alkaline conditions, which indicated importance of trehalose and arabitol for alkaliphily. Decreased pH resulted in the doubling of the proportion of phosphatidic acids among the membrane lipids, which was accompanied by a decrease in the fractions of phosphatidylcholines and sterols. Alkalitolerant fungi also exhibited a decrease in sterol level at decreased pH, but against the background of increased proportion of one of phospholipids. Decreased unsaturation degree in the fatty acids of the major phospholipids was a common response to decreased ambient pH.

New Record of Red Alga Thorea Hispida (Thore) Desv. (Rhodophyta) in Moscow River, Russia

In Moscow oblast, Thorea hispida (Thore) Desv. was first recorded at the beginning of the 20th century. Subsequently, T. hispida was found in 2004 in Moscow River within the territory of Moscow, where it still occurs. This species is included in the Red List of the Russian Federation, the Red List of Moscow oblast, and the Red Lists of some European countries. The new data on the distribution of T. hispida in Moscow River is presented in the paper, and some problems concerning the morphology and conservation status of this species are discussed.

Antimicrobial potential of alkalophilic micromycetes Emericellopsis alkalina

The ability of alkalophilic micromycetes of the Emericellopsis alkalinа to produce antimicrobial peptides has been studied. Evaluation of the spectrum and the yield of antibiotic compounds has allowed us to choose a promising producer of peptide antimycotics, Emericellopsis аlkalinа А118. The producer exhibits antifungal activity against conditionally pathogenic yeast and mold fungi, i.e., Candida аlbicans, Aspergillus niger, and A. fumigatus. The group of homologous active compounds isolated by the set of identified structural features (molecular weight, the ratio of the absorption at certain wavelengths, and the absence of initiation of Edman sequencing) may be attributed to peptaibols, which are a group of nonribosomal membrane-active antimicrobial peptides with a specificity of action primarily against fungi-micromycetes.

The first record of the brown alga Tinocladia crassa (Suringar) Kylin, 1940 in the White Sea

The study of the algal flora of the White Sea in July 2009 recorded the brown alga Tinocladia crassa (Chordariaceae, Ectocarpales) for the first time at Kasyan Island (Kandalaksha Bay). Observations of 2010–2014 confirmed and extended the species habitat. The new location expands the idea of the distribution of the species, which was found earlier only in the Pacific Ocean.