Mrakiella cryoconiti gen. nov., sp. nov., a psychrophilic, anamorphic, basidiomycetous yeast from alpine and arctic habitats

Abstract

). Two representatives were isolated from alpine glacier cryoconite and from northern Siberian sediment. Physiological and biochemical properties are similar to characteristics shared by members of the genus Mrakia, although sexual reproduction is absent. Mrakiella cryoconiti strains are psychrophilic and produce cold-active pectate lyase. Sequence analyses of the ITS and 26S rRNA D1/D2 regions indicated that these strains represent a distinct taxon within the Mrakia clade of the order Cystofilobasidiales, class Tremellomycetes and phylum Basidiomycota. On the basis of phenotypic and genotypic characteristics, Cryptococcus aquaticus (a member of the Mrakia clade) is transferred to the newly described genus as Mrakiella aquatica comb. nov. INTRODUCTIONThe order Cystofilobasidiales (Fell et al., 1999) includes teleomorph and anamorph genera. Psychrophily, i.e. the ability to grow and reproduce well at temperatures around 0 u C (Morita, 1975;Margesin et al., 2008), is a typical feature of the teliospore-producing genus Mrakia; the lowest growth temperature for Mrakia strains was reported to be 212 u C (Panikov & Sizova, 2007). Members of this genus have been isolated from numerous low-temperature environments in various regions, such as forest substrates in European Russia, glacier-preserved fossil lichens in Greenland, Antarctic soil or snow, glacial meltwater rivers in Patagonia, Argentina, and alpine Italian subglacial sediments, ice and meltwater, but also from frozen fish in Japan and frozen yoghurt in Brazil (Fell & Statzell-Tallman, 1998;Moreira et al., 2001;Bab'eva et al., 2002;Xin & Zhou, 2007;Turchetti et al., 2008). Some strains related to the species Mrakia frigida produce cold-active pectinolytic enzymes (Barnett et al., 2000;Nakagawa et al., 2004). These enzymes could be useful for a wide range of applications, such as the food industry for juice clarification below 5 u C or low-temperature pre-treatment of wastewater containing pectic substances. Two cold-active pectate-lyaseproducing strains (Margesin et al., 2005) were previously assigned to Mrakia frigida on the basis of internal transcribed spacer (ITS) and large-subunit (LSU) rRNA gene sequences. However, detailed investigation of the strains demonstrated the absence of teliospore production, which is characteristic of the genus Mrakia. In addition, ITS and LSU rRNA gene D1/D2 sequences indicate that these strains belong to a hitherto unknown genus and species, for which the name Mrakiella cryoconiti gen. nov., sp. nov. is proposed. METHODSSample collection and isolation. Yeast strain A15T was isolated from alpine glacier cryoconite collected from the Stubaier glacier near Innsbruck in Tyrol, Austria (altitude 2900 m above sea level) (Margesin et al., 2002). Strain AG25 originated from a sediment sample containing mud, spring water and moss, which was collected in the Gyda peninsula in northern Siberia (Gounot, 2001). Yeasts were maintained on R2A agar (Difco) plates; long-term storage was performed in 10 % (w/v) skimmed milk at 280 uC.Physiolog...

Myrmecridium hiemale sp. nov. from snow-covered alpine soil is the first eurypsychrophile in this genus of anamorphic fungi

“…They have developed particular physiological modifications, for example in enzyme activity, membrane fluidity and transport, as well as cold denaturation of proteins in order to survive and proliferate at low temperatures (D'Amico et al, 2006). Therefore, cold-adapted fungi have become important sources for the discovery of novel bioactive secondary metabolites and enzymes (Margesin & Fell, 2008;Margesin et al, 2009;Wang et al, 2015).…”

Psychrophilic yeasts from worldwide glacial habitats: diversity, adaptation strategies and biotechnological potential

“…Cryptococcus gilvescens accounted for over 50% of the total strains in Italian Alpine glaciers (Turchetti et al ., ). A handful of novel species were described for the first time (Table ) (Margesin et al ., , b; Margesin & Fell, ; Thomas‐Hall et al ., ; Turchetti et al ., ).…”

Bandoniozyma gen. nov., a Genus of Fermentative and Non-Fermentative Tremellaceous Yeast Species

“…The current diagnosis of the genus Cryptococcus accommodates the inclusion of fermentative isolates, but there are no currently recognized Cryptococcus species with this ability [21]. Cryptococcus aquaticus was once considered a fermentative Cryptococcus , but it was transferred to the genus Mrakiella , as M. aquatica [26]. As classification of yeasts in monophyletic taxa is highly desirable, the proposal of a new genus for this clade is justified rather than describing new yeast species of Cryptococcus , which would increase the polyphyletic nature of this genus.…”