Species composition of heterotrophic bacteria in the water of the Rybinek reservoir

: Twenty four cultures of heterotrophic bacteria were isolated from the water of the Rybinsk Reservoir on a medium containing organic matter. Bacteria belonging to the families Pseudomonadaceae and Achromobacteriaceae were most widely distributed; bacteria of the Mycobacteriaceae family were encountered less often. Predominating species which belonged to the genera Pseudomonas, Caulobacter, Flavobacterium, Mycobacterium, and Corynebacterium were isolated from the central part of the Reservoir. The special composition depended on the season. Bacteria of the Caulobacter genus were isolated mainly by the end of July and in May. Bacteria of the Corynebacterium genus predominated in March. Microflora belonging to the genera Pseudomonas and Flavobacterium was more constant. Bacteria isolated on media with the minimum content of organic matter (0.5 mg C per litre) belonged mainly to the Pseudomonas genus. Morphological, cultural, and physiological properties of the bacteria were studied. The bacteria grew on media containing carbohydrates and alcohols as a source of carbon though organic acids were assimilated to a less extent. The activity of catalase was found in the cultures, with an exception of the genera Caulobacter and Achromobacter.