Genome and physiology of the ascomycete filamentous fungus Xeromyces bisporus, the most xerophilic organism isolated to date. (7th October 2014)

• Record Type: Journal Article
• Authors: Leong, Su‐lin L.; Lantz, Henrik; Pettersson, Olga V.; Frisvad, Jens C.; Thrane, Ulf; Heipieper, Hermann J.; Dijksterhuis, Jan; Grabherr, Manfred; Pettersson, Mats; Tellgren‐Roth, Christian; Schnürer, Johan
• Is Part Of: Environmental microbiology. Volume 17:Number 2(2015:Feb.)
• Page Start: 496
• Page End: 513
• Publication Date: 2014-10-07
• Subjects: Microbial ecology -- Periodicals; Environmental Microbiology -- Periodicals; 579.17
• DOI: 10.1111/1462-2920.12596
• Languages: English
• ISSNs: 1462-2912

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p> <italic>X</italic> <italic>eromyces bisporus</italic> can grow on sugary substrates down to 0.61, an extremely low water activity. Its genome size is approximately 22 Mb. Gene clusters encoding for secondary metabolites were conspicuously absent; secondary metabolites were not detected experimentally. Thus, in its 'dry' but nutrient‐rich environment, <italic>X</italic><italic>. bisporus</italic> appears to have relinquished abilities for combative interactions. Elements to sense/signal osmotic stress, e.g. HogA pathway, were present in <italic>X</italic><italic>. bisporus</italic>. However, transcriptomes at optimal (∼ 0.89) versus low <italic>a</italic><sub>w</sub> (0.68) revealed differential expression of only a few stress‐related genes; among these, certain (not all) steps for glycerol synthesis were upregulated. <italic>X</italic><italic>eromyces bisporus</italic> increased glycerol production during hypo‐ and hyper‐osmotic stress, and much of its wet weight comprised water and rinsable solutes; leaked solutes may form a protective slime. <italic>X</italic><italic>eromyces bisporus</italic> and other food‐borne moulds increased membrane fatty acid saturation as water activity decreased. Such modifications did not appear to be transcriptionally regulated in <italic>X</italic><italic>. bisporus</italic>; however, genes modulating sterols, phospholipids and the cell wall were differentially expressed. <italic>X</italic><italic>eromyces bisporus</italic> was previously proposed to be a 'chaophile', preferring solutes that disorder biomolecular structures. Both <italic>X</italic><italic>. bisporus</italic> and the closely related xerophile, <italic>X</italic><italic>erochrysium xerophilum</italic>, with low membrane unsaturation indices, could represent a phylogenetic cluster of 'chaophiles'.</p> </abstract>