Studied is the nutrient requirements in growth factors among 199 Escherichia coli cultures, isolated from a series of water reservoirs in Karelia that differ in type and intensity of human impact. Revealed is the fact that auxotrophic E. coli were found in all surveyed reservoirs. Minimal percentage of E. coli that require in growth factors observed in the central part of Onega Lake. It is noted that the occurrence of auxotrophs depend on the level of water pollution. In the reservoirs that are experiencing intense anthropogenic pollution most isolates were multiple auxotroph. During cultivation of Escherichia coli isolates there were discovered auxotrophic variants in almost all amino acids. These results allow evaluating more objectively the results of environmental monitoring of natural microbial communities in general, and correct description of the processes of self-purification within water bodies.