Diversity and physiological and biochemical properties of heterotrophic bacteria isolated from Lake Baikal neuston

For heterotrophic microorganisms (44 strains) isolated from the surface film of Lake Baikal, identification was carried out and their physiological and biochemical characteristics were determined. Compared to the water column, diversity of cultured heterotrophs was low, indicating formation of stable microbial communities at the air–water interface. Heterotrophic bacteria isolated from the surface microlayer exhibited the enzymatic activity comparable to that for strains from other biofilm associations. Deinococcus ficus strain NA202 was the most active component of the community, capable of utilization of the broadest spectrum of mono- and disaccharides, sugars, and amino acids. This strain possessed the highest diversity of extracellular enzymes and was the most resistant to UV radiation. The physiological and biochemical properties of this strain may be responsible for its adaptation to survival in extreme conditions of the surface microlayer. These results improve our understanding of occurrence of UV-resistant strains in freshwater ecosystems.