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The respiration rate of 25 studied oligonitrophilous strains belonging to various genera and species of bacteria varied within wide limits depending on their taxonomy, conditions of cultivation, substrates, and other factors. No strict correlation was established between the respiration rate and the activity of nitrogen fixation. One of the typical properties of oligonitrophilous bacteria is a high rate of endogeneous respiration --50% and more of the respiration rate during assimilation of exogeneous substrates. The level of oxidative metabolism of oligonitrophilous bacteria was found to be higher on media containing bound nitrogen than on media without nitrogen.

Oligonitrophilic bacteria were cultivated on a medium containing only 2.5--10.0 mg/litre of nitrogen compounds. They assimilated elementary nitrogen only after utilization of these nitrogen compounds during growth and formation of nitrogen-fixing enzyme system. Their cells grown on a medium containing high concentrations of bound nitrogen did not fix nitrogen during further incubation in the atmosphere of 15N; therefore, the enzymes involved in nitrogen fixation were induced. These organisms are characterized by diauxia during their growth on media containing "start" doses of nitrogen. Enzymes catalysing nitrogen fixation in azotobacter are also induced. But, contrary to oligonitrophilic bacteria, the azotobacter does not require nitrogen compounds in the medium in order to adapt to molecular nitrogen, and its growth curve is not of a biphasal character. These data and the evidence of other authors suggest that all nitrogen-fixing microorganisms are characterized by the induced, not constitutive, enzymes involved in reduction of molecular nitrogen.

Mycobacterium flavum 158a can produce exopolysaccharides whose quantity varies, depending on the culture age, from 88.2 to 186.8% of the cell biomass weight in a medium with sucrose and from 1.3 to 25.0% in a medium with a polysaccharide synthesized by the oligonitrophilic bacterium Pseudomonas sp. 158a. The absolute and relative content of exopolysaccharides in the cultural broth decreases during the intensive growth of M. flavum 158a. This appears to be caused by their assimilation as a carbon source in the processes of energy and constructive metabolism. The exopolysaccharides of M. flavum 158a contain galactose, glucose, mannose, fucose, xylose, ramnose and a lipophilic sugar X1 at the molar ratio 10:11:11:8:11:12:16 as well as a non-identified sugar X2 with the Rf below than that of ramnose. The exopolysaccharide of M. flavum 158a was shown to be heterogeneous. It is composed of at least 16 fractions differing in molecular mass (from 98,980 to 490 D), quantity (from 2 to 8), composition and percentage of the constituent monosaccharides.

Exopolysaccharides from ten strains of oligonitrophilic bacteria were found to contain galactose, glucose and mannose. Strains belonging to the genus Mycobacterium contained also fucose, ramnose and three sugars that had not been identified: two of them were lipophilic and one had a lower Rf than ramnose. A correlation has been established between the composition of monosaccharides, their molar ratios in exocellular polysaccharides of oligonitrophilic bacteria, and the taxonomy of these microorganisms. Sporeforming bacteria belonging to the genus Bacillus produce polysaccharides which contain galactose, glucose and mannose at a ratio of 10:19: : (13--15). The molar ratio between the same sugars in exopolysaccharides of bacteria belonging to the genera Pseudomonas and Azotomonas is 10:(12--19) : (4--6). The ratio between galactose, glucose, mannose, fucose, ramnose, the unknown sugar and the sum of two lipophilic sugars in exocellular polysaccharides of the genus Mycobacterium is 10:(15--16) : (5--6) : (7--10) : (0.1--9) : (0.3--0.5) : (0.4--0.8).