Ecophysiological differences of environmental and clinical strains of opportunistic microfungus Aspergillus sydowii (Bain&Sart Thom&Churchстатья
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Аннотация:Aims: The goal of our research was to compare ecological and molecular genetic properties of opportunistic microfungi strains, with those of Aspergillus sydowii species, as an example.
Methods: DNA isolation, PCR and sequencing were conducted as previously described (Fomicheva et al., 2006). Radial growth rate (Kr) and sporulation were measured on Czapek agar at 5 - 40ºC temperature range and 0.99 - 0.80 water activity levels. Reproduction was measured by inoculating 1 ml of each strain spore suspension (1x106 spore/ml) in a flask with solid medium; after incubation spores were eluted and counted in a hemocytometer. Kr of the environmental and the clinical strains was also examined on Sabouraud, Hetchinson and water agar solid media. Additionally, consumption of a wider range of organic substances was determined using ECOLOG system.
Results: Sequence data of ITS1, 5.8S, ITS2, D1D2 28S rDNA genes yielded existence of two A. sydowii strain groups, each including both environmental and clinical strains. Nevertheless, certain ecophysiological differences between the environmental and clinical strains were shown. In unfavorable moisture conditions (0.90-0.80aw) active growth of the environmental strains was registered only at optimal temperature (30ºC). The clinical strains had high growth rates in a wider temperature interval (25-35ºC) at the same water activity levels. Sporulation of the clinical strains were 3-7 times higher at low water activity levels (0,95 and 0,90aw). The environmental and clinical strains differed in consumption of organic substrates. Growth rate of the clinical strains was twice higher on Sabouraud agar than that of the environmental isolates. According to ECOLOG system analysis the environmental strains grew better than the clinical isolates on a number of sugars typical for plants (arabinose, galactose, etc.).
Conclusions: From ecological viewpoint, the clinical strains A.sydowii are characterized by wider ecological amplitude, i.e. growth in a wider temperature and moisture range, higher spore production. The clinical strains were also able to grow under soil conditions. It remains to be investigated whether those opportunistic microfungi strains that have wider ecological amplitude are more capable of human body colonization or, on the contrary, they become more adaptive as a result of this interaction. The work was partly supported by grant № 11-04-00857 from the RFBR.