[Response of microbial communities of Lake Baikal to extreme temperatures].

The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal after exposure to extremely low temperatures (freeze-thawing) for different lengths of time have been first studied. It has been shown that short-term freezing (1-3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7- and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7- and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact.