Xeromyces Explained

Xeromyces is a monotypic genus of fungus in the family Monascaceae.^{[1] [2]} Its only species, Xeromyces bisporus, was first described by L.R. Fraser in 1954.^[3] No subspecies are listed in the Catalogue of Life.^[1]

It is a xerophile, being able to germinate at a water activity levels between 0.62 and 0.97,^[4] lower than any other known organism with the exception of Aspergillus penicillioides.^[5] However, it requires a higher water activity level to produce spores. It is a spoilage microbe in dry foods with high sugar contents, especially chocolate, honey, molasses, dried fruit or tobacco. Isolation of cultures requires media with 50% glucose.^[6]

The estimated genome size of X. bisporus is 24.8 Mb and the fungus lacks the genes normally associated with mycotoxin production.^[7]

It has unstalked cleistothecia, and each of its asci has two ascospores. Its simple asexual state consists of one or two round terminal chlamydospores.^[8]

Notes and References

1. Web site: Species 2000 & ITIS Catalogue of Life: 2011 Annual Checklist. . Bisby FA, Roskov YR, Orrell TM, Nicolson D, Paglinawan LE, Bailly N, Kirk PM, Bourgoin T, Baillargeon G, Ouvrard D . 2011 . Species 2000: Reading, UK. . 6 October 2017.
2. Species Fungorum. Kirk P.M., 2010-11-23
3. L.R. Fraser (1954), In: Proc. Linn. Soc. N.S.W. 78:245
4. Pitt JI, ((Christian JMB)) . Water relations of xerophilic fungi isolated from prunes . Applied Microbiology . 16 . 12 . 1968 . 1853–1858.
5. Stevenson A, Hamill PG, O'kane CJ, Kminek G, Rummel JD, Voytek MA, Dijksterhuis J, Hallsworth JE . 10.1111/1462-2920.13597 . free . Aspergillus penicillioides differentiation and cell division at 0.585 water activity . 2017 . Environmental Microbiology . 19 . 2 . 687–697.
6. Pettersson OV, Su-lin LL, Lantz H, Rice T, Dijksterhuis J, Houbraken J, Samson RA, Shnürer J . Phylogeny and intraspecific variation of the extreme xerophile, Xeromyces bisporus. . Fungal Biology . 2011 . 115 . 11 . 1100–1111 . 10.1016/j.funbio.2011.06.012 . 22036289.
7. Leong . Su-lin L. . Lantz . Henrik . Pettersson . Olga V. . Frisvad . Jens C. . Thrane . Ulf . Helpleper . Hermann J. . Dijksterhuls . Jan . Grabherr . Manfred . Pettersson . Mats . Tellgren-Roth . Christian . Schnürer . Johan . 2015 . Genome and physiology of the ascomycete filamentous fungus Xeromyces bisporus, the most xerophilic organism isolated to date . Environmental Microbiology . 17 . 2 . 496–513 . 10.1111/1462-2920.12596 . 25142400 . free .
8. Book: Jay, James M. . Modern Food Microbiology . Aspen Publishers, Inc. . Fifth . 1998 . Gaithersburg, Maryland . 31 . 978-0-8342-1230-5.