Characterization of heterotrophic microorganisms in alpine glacier cryoconite

We surveyed three samples of alpine glacier cryoconite for heterotrophic microbial life. All samples contained bacteria, yeasts, and hyphomycetes. Aerobic heterotrophic bacteria were more numerous than the other two group, and were isolated at all four cultivation temperatures (2 degreesC, 20degreesC, 37degreesC, 55degreesC). Significantly lower numbers of bacteria were able to grow at 2degreesC than at 20degreesC, while the opposite pattern was observed for yeasts. The majority of 66 selected bacterial isolates, able to grow at 2degreesC, were Gram-negative and could be assigned to two genera (Pseudomonas and Sphingonzonas). Among 17 yeast strains, we found three genera (Cryptoccus, Candida, and Rhodotorula). A considerable proportion of microorganisms utilized casein, carboxymethylcellulose (CMC), microorganfonic acid, starch, tributyrin, or diesel oil at 2degreesC. Significantly fewer microorganisms were able to grow on microcrystalline cellulose or keratin, or on aromatic hydrocarbons (naphthalene. phenanthrene, anthracene, or 4-chlorobiphenyl). The utilization of various carbon sources (CMC, starch, tributyrin, and diesel oil) by 14 selected yeast strains was inhibited at cultivation temperatures above 15degreesC.