Yeasts isolated from artificial lake waters

Abstract

Fourteen genera and 29 species of yeasts were found in the water of three artificial fresh lakes. The lakes, used for recreational purposes and located in the area of the Lowland Záhorie (Slovakia), were sampled in summer and autumn. Aureobasidium, Hansenula, Candida, and Rhodotorula species occurred the most frequently. The composition of yeast species was more heterogeneous in summer than in autumn. Relatively high population levels of fermentative and pellicle-forming yeasts were found, especially of Candida krusei and Hansenula anomala. The "black yeast" Aureobasidium pullulans was frequently isolated in autumn in high counts in contrast with the numbers of other species. Key words: ecology, yeasts, quantitative and qualitative study, freshwater lakes.

The occurrence of yeasts in the forest soils

“…The marked prevalence of basidiomycetous yeasts (94 -99%) is interesting. In comparison, the presence of ascomycetous and basidiomycetous yeasts in the water taken from lakes situated in this area was approximately equal (SLÁVIKOVÁ et al 1992). It appears from Table 2 that the great majority of yeasts isolated from forest soil lacked fermentative ability and thus depends on aerobic metabolism for its growth.…”

“…Sodium propionate (0.25%) was added to that part of medium which was used for cultivation at 25 GC. Colonies of different appearance were counted in both medium variants, and their representatives were purified according to SLÁVIKOVÁ et al (1992). Yeast counts were calculated as a number of colony-forming units (CFU) per dry gram of soil sample.…”

Yeasts colonizing the leaf surfaces

“…This "black yeast" is from an ecological point of view the ubiquitous species, found mainly on the phylloplane (Inácio et al 2002, Woody et al 2003. A. pullulans was the dominant species of water samples taken in autumn from the fish-pond (situated also in the forest park Železná Studnička) (Sláviková and Vadkertiová 1995) and artificial lake waters (located in the Lowland of Záhorie) (Sláviková and Vadkertiová 1992) when the water contained many fallen leaves. On the other hand, A. pullulans was seldom presented in the soil samples taken from the forest park Železná Studnička (Slávi-ková and Vadkertiová 2000).…”

Fungi in lake ecosystems

“…For many years it was assumed that yeasts are transients washed in from the phylloplane or the littoral zone, but there is now clear evidence for their more or less permanent residence in open water. In addition to Cryptococcus sp., several red and black yeast species occur in lake surface water (van Uden & Ahearn 1963, Woollett & Hedrick 1970, Slavikova et al 1992, Rosa et al 1995, Libkind et al 2003, Lefèvre et al 2007, and their production of photoprotective compounds is thought to be one of their adaptations as residents of surface waters (Libkind et al 2006). The yeast cell number correlates with the trophic status of the water body, ranging from oligotrophic to hypertrophic, and varies between 0.5 and 47 CFU ml -1 (annual averages) (Woollett & Hedrick 1970).…”