[Diversity and Physiological and Biochemical Properties of Heterotrophic Bacteria. Isolated from Lake Baikal Neuston.]

Abstract

For heterotrophic microorganisms (44 strains) isolated-from the surface film of Lake Baikal, iden- tification was carried out and their. physiological and biochemical characteristics were determined. Com- pared to the water column, diversity of cultured heterotrophs was low, indicating formation of stable micro- bial communities at the air-water interphase interface. Heterotrophic bacteria isolated from the surface mi- crolayer exhibited the enzymatic activity comparable to that for strains form other biofilm associations. Deinococcusfi6us strain NA202 'vas 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 bio- chemical properties of this strain may-be responsible for its adaptation to survival in extreme conditions of the surface microlayer. Our results improve our understanding of occurrence of UV-resistant strains in freshwater ecosystems.