Diversity and extracellular enzymatic activities of yeasts isolated from King George Island, the sub-Antarctic region

Abstract

BackgroundAntarctica has been successfully colonized by microorganisms despite presenting adverse conditions for life such as low temperatures, high solar radiation, low nutrient availability and dryness. Although these “cold-loving” microorganisms are recognized as primarily responsible for nutrient and organic matter recycling/mineralization, the yeasts, in particular, remain poorly characterized and understood. The aim of this work was to study the yeast microbiota in soil and water samples collected on King George Island.ResultsA high number of yeast isolates was obtained from 34 soil and 14 water samples. Molecular analyses based on rDNA sequences revealed 22 yeast species belonging to 12 genera, with Mrakia and Cryptococcus genera containing the highest species diversity. The species Sporidiobolus salmonicolor was by far the most ubiquitous, being identified in 24 isolates from 13 different samples. Most of the yeasts were psychrotolerant and ranged widely in their ability to assimilate carbon sources (consuming from 1 to 27 of the 29 carbon sources tested). All species displayed at least 1 of the 8 extracellular enzyme activities tested. Lipase, amylase and esterase activity dominated, while chitinase and xylanase were less common. Two yeasts identified as Leuconeurospora sp. and Dioszegia fristingensis displayed 6 enzyme activities.ConclusionsA high diversity of yeasts was isolated in this work including undescribed species and species not previously isolated from the Antarctic region, including Wickerhamomyces anomalus, which has not been isolated from cold regions in general. The diversity of extracellular enzyme activities, and hence the variety of compounds that the yeasts may degrade or transform, suggests an important nutrient recycling role of microorganisms in this region. These yeasts are of potential use in industrial applications requiring high enzyme activities at low temperatures.

Physiological adaptations of yeasts living in cold environments and their potential applications

“…victoriae, D. fristingensis, Leuconeurospora sp., Rh. larynges and W. anomalus (Carrasco et al 2012). Several yeasts and fungi isolates including Cryptococcus victoriae, Trichosporon pullulans and Geomyces pannorum, showed multiple enzymatic activities including lipase, cellulase and gelatinase, with higher activities at 4 and/or 20°C (Loperena et al 2012).…”

“…Chitinase activity was described in Antarctic yeast isolates D. fristingensis, Leuconeurospora sp., Metschnikowia sp., and Sporidiobolus salmonicolor (Carrasco et al 2012). A cold-adapted chitinase from G. antarctica that exhibited optimum activity at 15°C and pH 4.0 was expressed in P. pastoris, and its activity increased in presence of K ?…”

“…Protease activity was described in six unidentified yeasts isolated from alpine glacier cryoconite samples (Margesin et al 2003); in psychrotolerant Cr. gilvescens, Leuconeurospora sp., Mrakia gelida and Wickemanomyces anomalus isolated from subantarctic regions (Carrasco et al 2012); in Leucosporidiella sp. and L. creatinivora isolated from Antarctic marine sponges (Vaca et al 2013); in yeast belonging to Leucosporidiella, Udeniomyces, Mrakia and Mrakiella isolated from glacial ice of the Argentinian Patagonian Andes (de Garcia et al 2012); and in A. pullulans, Cryptococcus adeliensis, C. magnus, C. victoriae, Rhodotorula mucilaginosa and Rhodosporidium diobovatum isolated from an oligotrophic lake in Argentinian Patagonia (Brandao et al 2011).…”

“…Despite the suggestion that yeasts may be better adapted to low temperatures than bacteria (Shivaji and Prasad 2009), many studies have focused on bacteria; however, the number of reports describing the isolation of yeasts from cold environments is increasing (Guffogg et al 2004;Gilichinsky et al 2005;Russell 2006;de Garcia et al 2007;Turchetti et al 2008;Branda et al 2010;Pathan et al 2010;Thomas-Hall et al 2010;Turchetti et al 2011;Carrasco et al 2012;de Garcia et al 2012;Zhang et al 2012;Singh et al 2013). Considering that yeasts provide the benefits of single-cell fermentations and there are a large number of genetic tools to study and manipulate them, psychrophilic and psychrotolerant yeasts have attracted the attention of scientists for their potential application in various industries.…”

Purification and characterization of a novel α-glucosidase from an Antarctic yeast Dioszegia fristingensis isolate

“…Several Antarctic yeast species able to growth in media with soluble starch as unique carbon source and displaying extracellular soluble starch hydrolyzing activity have been reported [33,34]. From these yeasts, an isolate identified as Dioszegia fristingensis displayed the highest starch hydrolyzing activity.…”