Hortaea werneckii explained

Hortaea werneckii is a species of yeast in the family Teratosphaeriaceae.[1] It is a black yeast that is investigated for its remarkable halotolerance.[2] [3] While the addition of salt to the medium is not required for its cultivation, H. werneckii can grow in close to saturated NaCl solutions.[4] 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".

Several salt-tolerance mechanisms of H. werneckii have been studied on molecular level. For example, it is known that its major compatible solutes are glycerol, erythritol, arabitol, and mannitol; melanin accumulation of the cell wall aids in retention of at least glycerol inside of the cell.[3] Several components of the high osmolarity glycerol (HOG) signalling pathway (which controls responses to osmotic shock) have been studied in detail and some seem to differ in function compared to their counterparts in Saccharomyces cerevisiae.[5] [6] [7] Adaptation to high concentrations of salt are also accompanied by changes in membrane lipid composition, mainly by increasing the unsaturation of the phospholipid fatty acids.[8] [9]

H. werneckii causes a rare superficial and non-invasive skin infection tinea nigra.[10] The typical symptoms are non-scaly, smooth, brown-black painless spots on the palms of hands and soles of feet.

The growth of H. werneckii in liquid media is often yeast-like, although it can switch to filamentous growth. The mechanism of the switch is not known. The cells appear brown because of melanin production.[3]

Whole genome sequencing of H. werneckii[11] [12] revealed a recent whole genome duplication, thought to be the only reported whole-genome duplication among ascomycetous yeasts besides the better known one in the Saccharomyces cerevisiae lineage.[13] Based on genome sequencing of additional strains, 10 out of 12 strains have a genome that was duplicated by several hybridizations between haploid strains, yielding formed stable diploids. Apart from these hybridization events, no signs of sexual reproduction were found.[14] As a consequence, the genome of H. werneckii is relatively large (49.9 Mb) with 15974 predicted genes. Genes encoding metal cation transporters, which are thought to play a role in halotolerance, experienced several additional gene duplications at various points during their evolution.

A homothallic mating locus was found in all sequenced genomes, although one of the mating genes may have been inactivated in some strains. Despite this, phylogenetic analyses and linkage disequilibrium analyses indicate that H. werneckii is asexual.

Notes and References

  1. Web site: Hortaea werneckii . 2009-08-10 . dead . https://web.archive.org/web/20090821133357/http://www.doctorfungus.org/thefungi/hortaea.htm . 2009-08-21 .
  2. Gunde-Cimerman N, Ramos J, Plemenitas A . Halotolerant and halophilic fungi . Mycological Research . 113 . Pt 11 . 1231–41 . November 2009 . 19747974 . 10.1016/j.mycres.2009.09.002 .
  3. Kogej T, Stein M, Volkmann M, Gorbushina AA, Galinski EA, Gunde-Cimerman N . Osmotic adaptation of the halophilic fungus Hortaea werneckii: role of osmolytes and melanization . Microbiology . 153 . Pt 12 . 4261–73 . December 2007 . 18048939 . 10.1099/mic.0.2007/010751-0 . free .
  4. Gostinčar C, Lenassi M, Gunde-Cimerman N, Plemenitaš A . Fungal adaptation to extremely high salt concentrations . Advances in Applied Microbiology . 77 . 71–96 . 2011 . 22050822 . 10.1016/B978-0-12-387044-5.00003-0 . 9780123870445 .
  5. Turk M, Plemenitas A . The HOG pathway in the halophilic black yeast Hortaea werneckii: isolation of the HOG1 homolog gene and activation of HwHog1p . FEMS Microbiology Letters . 216 . 2 . 193–9 . November 2002 . 12435502 . 10.1111/j.1574-6968.2002.tb11435.x . free .
  6. Lenassi M, Vaupotic T, Gunde-Cimerman N, Plemenitas A . The MAP kinase HwHog1 from the halophilic black yeast Hortaea werneckii: coping with stresses in solar salterns . Saline Systems . 3 . 3 . March 2007 . 17349032 . 1828057 . 10.1186/1746-1448-3-3 . free .
  7. Fettich M, Lenassi M, Veranič P, Gunde-Cimerman N, Plemenitaš A . Identification and characterization of putative osmosensors, HwSho1A and HwSho1B, from the extremely halotolerant black yeast Hortaea werneckii . Fungal Genetics and Biology . 48 . 5 . 475–84 . May 2011 . 21281727 . 10.1016/j.fgb.2011.01.011 .
  8. Turk M, Méjanelle L, Sentjurc M, Grimalt JO, Gunde-Cimerman N, Plemenitas A . Salt-induced changes in lipid composition and membrane fluidity of halophilic yeast-like melanized fungi . Extremophiles . 8 . 1 . 53–61 . February 2004 . 15064990 . 10.1007/s00792-003-0360-5 . 20139110 .
  9. Gostincar C, Turk M, Plemenitas A, Gunde-Cimerman N . The expressions of Delta 9-, Delta 12-desaturases and an elongase by the extremely halotolerant black yeast Hortaea werneckii are salt dependent . FEMS Yeast Research . 9 . 2 . 247–56 . March 2009 . 19220869 . 10.1111/j.1567-1364.2009.00481.x . free .
  10. Reid BJ . Exophiala werneckii causing tinea nigra in Scotland . The British Journal of Dermatology . 139 . 1 . 157–8 . July 1998 . 9764175 . 10.1046/j.1365-2133.1998.02340.x . 70450832 .
  11. Lenassi M, Gostinčar C, Jackman S, Turk M, Sadowski I, Nislow C, Jones S, Birol I, Cimerman NG, Plemenitaš A . Whole genome duplication and enrichment of metal cation transporters revealed by de novo genome sequencing of extremely halotolerant black yeast Hortaea werneckii . PLOS ONE . 8 . 8 . e71328 . 2013 . 23977017 . 3744574 . 10.1371/journal.pone.0071328 . 2013PLoSO...871328L . free .
  12. Sinha S, Flibotte S, Neira M, Formby S, Plemenitaš A, Cimerman NG, Lenassi M, Gostinčar C, Stajich JE, Nislow C . Hortaea werneckii: Combining an Improved Genome with Gene Expression and Chromatin Structure . G3 . 7 . 7 . 2015–2022 . July 2017 . 28500048 . 5499112 . 10.1534/g3.117.040691 .
  13. Dujon B . Basic principles of yeast genomics, a personal recollection . FEMS Yeast Research . 15 . 5 . fov047 . August 2015 . 26071597 . 10.1093/femsyr/fov047 . free .
  14. Gostinčar C, Stajich JE, Zupančič J, Zalar P, Gunde-Cimerman N . Genomic evidence for intraspecific hybridization in a clonal and extremely halotolerant yeast . BMC Genomics . 19 . 1 . 364 . May 2018 . 29764372 . 5952469 . 10.1186/s12864-018-4751-5 . free .

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