Abstract
Ascospores of Neosartorya, Byssochlamys and Talaromyces can be regarded as the most stress-resistant eukaryotic cells. They can survive exposure at temperatures as high as 85°C for 100 min or more. Neosartorya fischeri ascospores are more viscous and more resistant to the combined stress of heat and desiccation than the ascospores of Talaromyces macrosporus which contain predominantly trehalose. These ascospores contain trehalose-based oligosaccharides (TOS) that are novel compatible solutes, which are accumulated to high levels. These compounds are also found in other members of the genus Neosartorya and in some other genera within the order Eurotiales that also include Byssochlamys and Talaromyces. The presence of oligosaccharides was observed in species that had a relatively high growth temperature. TOS glasses have a higher glass transition temperature (Tg) than trehalose, and they form a stable glass with crystallizing molecules, such as mannitol. Our data indicate that TOS are important for prolonged stabilization of cells against stress. The possible unique role of these solutes in protection against dry heat conditions is discussed.
Highlights
Stress-resistant ascospores are found among the fungal genera Neosartorya, Byssochlamys and Talaromyces
trehalose-based oligosaccharides (TOS) glasses have a higher glass transition temperature (Tg) than trehalose, and they form a stable glass with crystallizing molecules, such as mannitol
Ascospores of Neosartorya fischeri exposed to extreme heat (95°C) at a relative humidity (RH) of 30% had a D-value almost 200 times higher than spores exposed to a RH of 75% (Gomez et al, 1994)
Summary
Stress-resistant ascospores are found among the fungal genera Neosartorya, Byssochlamys and Talaromyces These spores resist high temperature, pressure and desiccation (Beuchat, 1986; Dijksterhuis and Samson, 2002; 2006; Reyns et al, 2003; Dijksterhuis and Teunissen, 2004; Dijksterhuis et al, 2007; Houbraken et al, 2012a) and are arguably the most stress-resistant eukaryotic cells described to date, with a temperature resistance similar to Bacillus subtilis spores (Dijksterhuis and Teunissen, 2004). Ascospores of Neosartorya fischeri exposed to extreme heat (95°C) at a relative humidity (RH) of 30% had a D-value (decimal reduction time, or the time that is required to kill 90% of the spores) almost 200 times higher than spores exposed to a RH of 75% (Gomez et al, 1994)
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