Isotope Composition of Nitrogen and Stoichiometric Ratios of Elements in Biomass of Spirogyra in Lake Baikal.

Using stable isotope analysis of nitrogen, for the first time the hypothesis on different sources of inorganic nutrients for two groups of littoral algae in Lake Baikal was confirmed. Strongly attached filamentous algae of genus Ulothrix, which developed in the wave-braking zone at depth 0.5 m, and loosely attached filamentous algae of genus Spirogyra, which developed in deeper layers 3.0-5.0 m in a low-turbulence zone, get inorganic nutrients presumably from surface discharge and groundwater inputs, respectively. Besides, stoichiometric ratios C:N and N:P in biomass of the algae indicated that growth of Spirogyra in Lake Baikal was likely limited by nitrogen, while growth of Ulothrix was limited by phosphorus.

[Dynamics of variability of microbiotes of the cavity of the mouth and the great intestinent of young men when changing the conditions of life.]

The purpose of the work is to determine the spectrum, quantity and frequency of occurrence of microorganisms in the oral fluid and large intestine in healthy young men under changes of living conditions. A survey was conducted of 14 nonresident young men, students of the 1st and 2nd courses, studying at Tver State Medical University, which included questions about the place of birth, living conditions, the presence of chronic diseases and the frequency of their exacerbations over the past year, water and food regimes, physical exertion, the presence of bad habits and emotional stress, etc. The oral fluid and feces were examined to determine the spectrum and amount of microbiota of the upper and lower parts of the gastrointestinal tract. As the result of the survey, it was found that the living conditions of all young men significantly worsened among second-year students than freshmen. It was revealed that colon microbiota in sophomores characterized by less diverse than those of first-year, despite of a marked increase in the number of opportunistic pathogens (Stаphylocоccus spp., Strерtocoсcus spp., Clоstridium spp., Васillus spp., Кlebsiеlla spp.) over resident microbes. It was found the decrease in the number and frequency of occurrence of all microbial representatives in the oral microbiota of 2nd year students in comparison with first-year. It was proved that the deterioration of living conditions of nonresident students led to the increase in the number of second-year students with dysbiotic changes in the intestinal microbiota from 86% to 100%, mainly due to the increase in the number of persons with dysbiosis of II and III degree.