Wallemia ichthyophaga

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Wallemia ichthyophaga
WiMicro.tif
Micrograph showing characteristic sarcina-like morphology of W. ichthyophaga and crystals of NaCl.
Scientific classification
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W. ichthyophaga
Binomial name
Wallemia ichthyophaga

Wallemia ichthyophaga is one of the three species of fungi in the genus Wallemia, which in turn is the only genus of the class Wallemiomycetes. [1] The phylogenetic origin of the lineage was placed to various parts of Basidiomycota, but according to the analysis of larger datasets it is a (495-million-years-old) sister group of Agaricomycotina. [2] [3] Although initially believed to be asexual, population genomics found evidence of recombination between strains and a mating type locus was identified in all sequenced genomes of the species. [3] [4]

Only a limited number of strains of W. ichthyophaga have been isolated so far (from hypersaline water of solar salterns, bitterns (magnesium-rich residual solutions in salt production from sea water) and salted meat). [1]

W. ichthyophaga requires at least 1.5 M NaCl for in-vitro growth (or some other osmolyte for an equivalent water activity), and it thrives even in saturated NaCl solution. This makes it the most halophilic fungus known and distinguishes it from halotolerant (e.g. Aureobasidium pullulans ) and extremely halotolerant fungi (e.g. Hortaea werneckii ), which are able to grow well even in the absence of salt in the medium. [5] Inability to grow without salt is an exception in the fungal kingdom, but is common in halophilic Archaea. [6]

The fungus grows in the form of sarcina-like structures, or compact multicellular clumps. [1] These increase in size almost four-fold when exposed to high salinity, and the cell wall experiences a three-fold thickening. This results in a substantially decreased functional cell volume and is thought to be one of the halotolerance mechanisms of this species. [7]

The whole genome sequencing of W. ichthyophaga revealed that it has one of the smallest of all sequenced basidiomycetous genomes (9.6 Mbp, only 4884 predicted proteins). [3] Contrary to what was observed for the extremely halotolerant H. werneckii , in W. ichthyophaga there are almost no expansions in metal cation transporter genes and their expression is not salt-responsive. On the other hand, there is a vast enrichment of hydrophobins (proteins of cell wall with diverse functions and many biotechnological uses), which contain an unusually high proportion of acidic amino acids. [3] High proportion of acidic amino acids is thought to be an adaptation of proteins to high concentrations of salt. [8] After sequencing the genomes of nearly all known strains of W. ichthyophaga, population genomic analysis showed that the species forms a single recombining population. [4]

Related Research Articles

A halophile is an extremophile that thrives in high salt concentrations. In chemical terms, halophile refers to a Lewis acidic species that has some ability to extract halides from other chemical species.

Halotolerance is the adaptation of living organisms to conditions of high salinity. Halotolerant species tend to live in areas such as hypersaline lakes, coastal dunes, saline deserts, salt marshes, and inland salt seas and springs. Halophiles are organisms that live in highly saline environments, and require the salinity to survive, while halotolerant organisms can grow under saline conditions, but do not require elevated concentrations of salt for growth. Halophytes are salt-tolerant higher plants. Halotolerant microorganisms are of considerable biotechnological interest.

<span class="mw-page-title-main">Basidiomycota</span> Division of fungi

Basidiomycota is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basidiomycota includes these groups: agarics, puffballs, stinkhorns, bracket fungi, other polypores, jelly fungi, boletes, chanterelles, earth stars, smuts, bunts, rusts, mirror yeasts, and Cryptococcus, the human pathogenic yeast.

<span class="mw-page-title-main">Hydrophobin</span>

Hydrophobins are a group of small cysteine-rich proteins that were discovered in filamentous fungi that are lichenized or not. Later similar proteins were also found in Bacteria. Hydrophobins are known for their ability to form a hydrophobic (water-repellent) coating on the surface of an object. They were first discovered and separated in Schizophyllum commune in 1991. Based on differences in hydropathy patterns and biophysical properties, they can be divided into two categories: class I and class II. Hydrophobins can self-assemble into a monolayer on hydrophilic:hydrophobic interfaces such as a water:air interface. Class I monolayer contains the same core structure as amyloid fibrils, and is positive to Congo red and thioflavin T. The monolayer formed by class I hydrophobins has a highly ordered structure, and can only be dissociated by concentrated trifluoroacetate or formic acid. Monolayer assembly involves large structural rearrangements with respect to the monomer.

<i>Aureobasidium pullulans</i> Species of fungus

Aureobasidium pullulans is a ubiquitous and generalistic black, yeast-like fungus that can be found in different environments. It is well known as a naturally occurring epiphyte or endophyte of a wide range of plant species without causing any symptoms of disease. A. pullulans has a high importance in biotechnology for the production of different enzymes, siderophores and pullulan. Furthermore, A. pullulans is used in biological control of plant diseases, especially storage diseases.

Pathogenic fungi are fungi that cause disease in humans or other organisms. Although fungi are eukaryotic, many pathogenic fungi are microorganisms. Approximately 300 fungi are known to be pathogenic to humans; their study is called "medical mycology". Fungal infections kill more people than either tuberculosis or malaria—about 2 million people per year.

<i>Hortaea werneckii</i> Species of fungus

Hortaea werneckii is a species of yeast in the family Teratosphaeriaceae. It is a black yeast that is investigated for its remarkable halotolerance. While the addition of salt to the medium is not required for its cultivation, H. werneckii can grow in close to saturated NaCl solutions. To emphasize this unusually wide adaptability, and to distinguish H. werneckii from other halotolerant fungi, which have lower maximum salinity limits, some authors describe H. werneckii as "extremely halotolerant".

Geomyces is a genus of filamentous fungi in the family Myxotrichaceae. Members of the genus are widespread in distribution, especially in northern temperate regions. Known to be psychrotolerant and associated with Arctic permafrost soils, they are equally prevalent in the air of domestic dwellings, and children's sandpits. Species of Geomyces have previously been placed in the genus Chrysosporium.

<span class="mw-page-title-main">Wallemiomycetes</span> Class of fungi

The Wallemiomycetes are a class of fungi in the division Basidiomycota. It consists of the single order Wallemiales, containing the single family Wallemiaceae, which in turn contains the single genus Wallemia. The phylogenetic origin of the lineage was placed to various parts of Basidiomycota, but according to the analysis of a larger dataset it is a sister group of Agaricomycotina. The genus contains species of xerophilic molds that are found worldwide. The seven described species are distinguished by conidial size, xerotolerance, halotolerance, chaotolerance, growth temperature regimes, extracellular enzyme activity profiles, and secondary metabolite patterns. They are typically isolated from low-moisture foods, indoor air dust, salterns and soil. W. sebi is thought to be one of the causes of the hypersensitivity pneumonitis known as the farmer's lung disease, but since the other species were recognised and separated from W. sebi only recently, their role in the disease cannot be excluded.

Black yeasts, sometimes also black fungi, dematiaceous fungi, microcolonial fungi or meristematic fungi is a diverse group of slow-growing microfungi which reproduce mostly asexually. Only few genera reproduce by budding cells, while in others hyphal or meristematic (isodiametric) reproduction is preponderant. Black yeasts share some distinctive characteristics, in particular a dark colouration (melanisation) of their cell wall. Morphological plasticity, incrustation of the cell wall with melanins and presence of other protective substances like carotenoids and mycosporines represent passive physiological adaptations which enable black fungi to be highly resistant against environmental stresses. The term "polyextremotolerance" has been introduced to describe this phenotype, an example of which is the species Aureobasidium pullulans. Presence of 1,8-dihydroxynaphthalene melanin in the cell wall confers to the microfungi their characteristic olivaceous to dark brown/black colour.

<i>Wallemia sebi</i> Species of fungus

Wallemia sebi is a xerophilic fungus of the phylum Basidiomycota.

Previously classified under the species complex Aureobasidium pullulans, Aureobasidium subglaciale is a black yeast-like, extremophile, ascomycete fungus that is found in extreme cold habitats. The species was originally isolated from subglacial ice of arctic glaciers. The first isolate of this species was obtained from subglacial ice of the Norwegian island Spitsbergen, one of the coldest places inhabited by humans. of Genomic data collected from specimens in the Aureobasidium pullulans complex justified distinction of four different species

Aureobasidium melanogenum, formerly known as Aureobasidium pullulans var. melanogenum is a ubiquitous black, yeast-like fungus that is found mainly in freshwater habitats. The species also includes strains causing human infections, which were previously classified as A. pullulans. It was named due to abundant melanin production and accumulation in the cell walls, which leads to dark green, brown or black appearance of the cells and colonies The species was established when the genomes of the four former varieties of Aureobasidium pullulans were sequenced and the large differences between them were discovered.

Aureobasidium namibiae, formerly known as Aureobasidium pullulans var. namibiae is a ubiquitous black, yeast-like fungus. It was described on the basis of only one strain isolated from dolomitic marble in Namibia. The species was established when the genomes of the four former varieties of Aureobasidium pullulans were sequenced and the large differences between them were discovered.

<i>Cladosporium sphaerospermum</i> Species of fungus

Cladosporium sphaerospermum is a radiotrophic fungus belonging to the genus Cladosporium and was described in 1886 by Albert Julius Otto Penzig from the decaying leaves and branches of Citrus. It is a dematiaceous (darkly-pigmented) fungus characterized by slow growth and largely asexual reproduction. Cladosporium sphaerospermum consists of a complex of poorly morphologically differentiated, "cryptic" species that share many physiological and ecological attributes. In older literature, all of these sibling species were classified as C. sphaerospermum despite their unique nature. Accordingly, there is confusion in older literature reports on the physiological and habitat regularities of C. sphaerospermum in the strict sense. This fungus is most phylogenetically similar to C. fusiforme. According to modern phylogenetic analyses, the previously synonymized species, Cladosporium langeroni, is a distinct species.

Aspergillus olivicola is a species of fungus in the genus Aspergillus. It is from the Nidulantes section. The species was first described in 2008. It has been isolated from fruit in Italy. A. olivicola has been shown to produce aflatoxin B1, emericellin, shamixanthone, siderin, sterigmatocystin, terrein, and varitriol.

Wallemia mellicola is a xerophilic fungus of the phylum Basidiomycota, described in 2015 upon taxonomic revision of the species Wallemia sebi. A large amount of published research referring to W. sebi was likely actually performed on W. mellicola. An example of this is the sequencing of the W. mellicola genome, which was published under the name of W. sebi.

Fungal genomes are among the smallest genomes of eukaryotes. The sizes of fungal genomes range from less than 10 Mbp to hundreds of Mbp. The average genome size is approximately 37 Mbp in Ascomycota, 47 Mbp in Basidiomycota and 75 Mbp in Oomycota. The sizes and gene numbers of the smallest genomes of free-living fungi such as those of Wallemia ichthyophaga, Wallemia mellicola or Malassezia restricta are comparable to bacterial genomes. The genome of the extensively researched yeast Saccharomyces cerevisiae contains approximately 12 Mbp and was the first completely sequenced eukaryotic genome. Due to their compact size fungal genomes can be sequenced with less resources than most other eukaryotic genomes and are thus important models for research. Some fungi exist as stable haploid, diploid, or polyploid cells, others change ploidy in response to environmental conditions and aneuploidy is also observed in novel environments or during periods of stress.

<i>Aureobasidium</i> Genus of fungi

Aureobasidium is a genus of fungi belonging to the family Dothioraceae.

References

  1. 1 2 3 Zalar, P.; Sybren De Hoog, G.; Schroers, H. J.; Frank, J. M.; Gunde-Cimerman, N. (2005). "Taxonomy and phylogeny of the xerophilic genus Wallemia (Wallemiomycetes and Wallemiales, cl. Et ord. Nov.)". Antonie van Leeuwenhoek. 87 (4): 311–328. doi:10.1007/s10482-004-6783-x. PMID   15928984. S2CID   4821447.
  2. Padamsee, M.; Kumar, T. K. A.; Riley, R.; Binder, M.; Boyd, A.; Calvo, A. M.; Furukawa, K.; Hesse, C.; Hohmann, S.; James, T. Y.; Labutti, K.; Lapidus, A.; Lindquist, E.; Lucas, S.; Miller, K.; Shantappa, S.; Grigoriev, I. V.; Hibbett, D. S.; McLaughlin, D. J.; Spatafora, J. W.; Aime, M. C. (2012). "The genome of the xerotolerant mold Wallemia sebi reveals adaptations to osmotic stress and suggests cryptic sexual reproduction" (PDF). Fungal Genetics and Biology. 49 (3): 217–226. doi:10.1016/j.fgb.2012.01.007. PMID   22326418.
  3. 1 2 3 4 Zajc, J.; Liu, Y.; Dai, W.; Yang, Z.; Hu, J.; Gostin Ar, C.; Gunde-Cimerman, N. (2013). "Genome and transcriptome sequencing of the halophilic fungus Wallemia ichthyophaga: Haloadaptations present and absent". BMC Genomics. 14: 617. doi: 10.1186/1471-2164-14-617 . PMC   3849046 . PMID   24034603.
  4. 1 2 Gostinčar, Cene; Sun, Xiaohuan; Zajc, Janja; Fang, Chao; Hou, Yong; Luo, Yonglun; Gunde-Cimerman, Nina; Song, Zewei (2019). "Population Genomics of an Obligately Halophilic Basidiomycete Wallemia ichthyophaga". Frontiers in Microbiology. 10: 2019. doi: 10.3389/fmicb.2019.02019 . ISSN   1664-302X. PMC   6738226 . PMID   31551960.
  5. Gostinčar, C.; Lenassi, M.; Gunde-Cimerman, N.; Plemenitaš, A. (2011). Fungal Adaptation to Extremely High Salt Concentrations. Advances in Applied Microbiology. Vol. 77. pp. 71–96. doi:10.1016/B978-0-12-387044-5.00003-0. ISBN   9780123870445. PMID   22050822.
  6. Gostinčar, C.; Grube, M.; De Hoog, S.; Zalar, P.; Gunde-Cimerman, N. (2010). "Extremotolerance in fungi: Evolution on the edge". FEMS Microbiology Ecology. 71 (1): 2–11. Bibcode:2010FEMME..71....2G. doi: 10.1111/j.1574-6941.2009.00794.x . PMID   19878320.
  7. Kralj Kuncic, M.; Kogej, T.; Drobne, D.; Gunde-Cimerman, N. (2009). "Morphological Response of the Halophilic Fungal Genus Wallemia to High Salinity". Applied and Environmental Microbiology. 76 (1): 329–337. doi:10.1128/AEM.02318-09. PMC   2798636 . PMID   19897760.
  8. Madern, D.; Ebel, C.; Zaccai, G. (2000). "Halophilic adaptation of enzymes". Extremophiles: Life Under Extreme Conditions. 4 (2): 91–98. doi:10.1007/s007920050142. PMID   10805563. S2CID   32590023.