[Method for assaying methane monooxygenase activity by measuring methane uptake in the reaction vessel]. / Opredelenie aktivnosti metanmonooksigenazy po ubyli metana b reaktsionnoi srede.

The reaction vessel has been designed to measure methane monooxygenase activity. An elastic membrane has been built into one of the walls of the vessel to take liquid samples, avoiding formation of the gaseous phase in the reaction volume. The methane content in the samples is measured in a gas-liquid chromatograph with a flame ionization detector in two ways: 1. by direct measurement of methane in the liquid sample, and 2. by measurement of methane in the gaseous phase after methane diffusion from the liquid sample into the gaseous space of another vessel. The method is simple, sensitive (with a lower limit of 0.1 nMole CH4), and well reproducible. This method permits measurement of the oxidation kinetics of methane and other gaseous hydrocarbons both by intact cells and cell-free preparations of methane oxidizing bacteria.

[Symbiosis between the nodule bacterium Sinorhizobium meliloti and alfalfa (Medicago sativa) under salinization conditions].

Two hundred forty-three isolates of alfalfa nodule bacteria (Sinorhizobium meliloti) were obtained from legume nodules and soils sampled in the northern Aral region, experiencing secondary salinization. Isolates obtained from nodules (N isolates) were significantly more salt-tolerant than those from soils (S isolates) when grown in a liquid medium with 3.5% NaCl. It was found that wild species of alfalfa, melilot, and trigonella preferably formed symbioses with salt-tolerant nodule bacteria in both salinized and nonsalinized soils. Only two alfalfa species, Medicago falcata and M. trautvetteri, formed efficient symbioses in soils contrasting in salinity. The formation of efficient symbiosis with alfalfa in the presence of 0.6% NaCl was studied in 36 isolates (N and S) differing in salt tolerance and symbiotic efficiency. Fifteen isolates formed efficient symbioses in the presence of salt. The increase in the dry weight of the plants was 25-68% higher than in the control group. The efficiency of symbiotic interaction under salinization conditions depended on the efficiency of the isolates under standard conditions but did not correlate with the source of nodule bacteria (soil or nodule) or their salt tolerance. The results indicate that nodule bacterium strains forming efficient symbioses under salinization conditions can be found.

[Isotopic effect in enzymatic oxidation of methane]. / Izotopnyi effekt v fermentativnom okislenii metana

The isotopic effect during oxidation of methane and deuteromethane by a suspension of Methylomonas rubrum cells, for which methane is the only source of carbon, was observed. The rate of CH4 oxidation is 12.5 times higher than that of CH4 oxidation. It is demonstrated that CD4 is a competitive inhibitor of CH4 oxidation. The results obtained suggest that the disruption of the C-H bond is the limiting step of enzymatic oxidation of methane.