[Survival of bacteria in the Artificial Mars unit].

The survival of bacteria was studied in the "Artificial Mars" apparatus reproducing a complex of physical extreme factors. Bacteria isolated from microbiocenoses subjected to the action of chemical extreme factors (hydrogen peroxide, catalytically active minerals) were shown to be most resistant among soil heterotrophic bacteria. Cells in the resting state caused by dehydration survived better than vegetative cells.

[Use of a method of concentrating microorganisms in an electric field in the search for life in Mars].

The paper describes a technique of concentrating microorganisms from filtrates obtained from mixtures of the Martian ground analogs and desert soil using electroretention on polarizable carriers (sterilized cotton wool or gauze). The degree of retention can reach 99.9% at a field intensity of 50 V/cm and a flow rate of 0.

Biological studies of Martian soil analogues.

Results of the study of the influence of Martian soil analogues, both as described by American scientists and as prepared by us, and of hydrogen peroxide on the viability of microorganisms are presented. The experiments were carried out using mixtures of soil analogues with desert soil and black earth (chernozem) samples, and pure cultures of microorganism. Microorganisms capable of withstanding a concentration of hydrogen peroxide in the medium as high as 1.

[Search for life on Mars].

The paper presents the data about the catalytic activity of several minerals from the Martian ground and of some laboratory analogues of the planet ground. It has been shown that it is possible to obtain unambigious data about life on Mars by using such methodological approaches which are based on biological principles of the determination of living matter. Microbiological methods for detection of extraterrestrial life should be preferred in future over biogeochemical methods which were used by the Viking stations.

[Effect of hydrogen peroxide and hydrated ferric oxides on the metabolism of soil microflora].

The effect of hydrogen peroxide and the mineral limonite on the rate of microbial processes was studied in poor and rich soils. The dynamics of CO2 evolution can be registered upon addition of hydrogen peroxide to chernozem samples, which confirms the existence of metabolism of soil microorganisms. In experiments with desert soil, the evolution of O2 increases rather than that of CO2, which is probably due to an increase in the number of microorganisms producing catalase.

[Possibility of the nonbiological binding of CO2 and CO by the components of Martian soil].

A mixture of carbon dioxide and carbon monoxide was irradiated in the presence of limonite and hydrogen peroxide at 340 nm. As has been demonstrated by gas chromatography, chemical reactions occurring in this case yield organic compounds which could be synthesized in the experiments conducted by the Viking stations. Consequently, this method cannot discriminate between the chemical and biological processes which possibly accounted for positive signals registered in the experiments of the Viking stations.

[Determination of carbon dioxide released from soil at different humidities].

The detection of soil microorganisms by their evolution of carbon dioxide does not always correlate with the number of microorganisms and the rate of biochemical processes in soil. New microbial populations appear in the incubation chamber as the concentration of carbon dioxide increases; this results in an increase in the activity of such processes as photosynthesis, chemosynthesis and heterotrophic assimilation of carbon dioxide. Life detection on other planets by determining carbon dioxide evolved from the ground may lead to erroneous conclusions on the presence of microorganism in the ground.

[Gas chromatographic study of broth cultures of microorganisms as a method of detecting extraterrestrial life].

The method of pyrolysis--gas chromatography was used to study the composition of cultural liquids obtained upon the incubation of desert soil samples in a rich growth medium. The composition of pyrolysis products was found to depend on the time of incubation. Cultural liquids differed in their composition from the original growth medium.

[Origin of the oxygen detected by the Viking stations in an analysis of Mars soil].

Reactions between the mineral limonite and hydrogen peroxide were studied and gases produced thereupon were analysed by gas chromatography. Oxygen did not evolve if limonite was added to hydrogen peroxide frozen at a temperature of dry ice. However, at room temperature, a vigorous chemical reaction occurred and a large amount of oxygen evolved.

[Optimal conditions for determing ATP of microbial origin].

Endogenous luminescence of the luciferin-luciferase extract from firely tails was studied in determing low concentrations of ATP. The optimum concentration of the the extract, corresponding to the minumum effect of endogenous luminescence, was found in the reaction medium. The solution of luciferin-luciferase was unstable at room temperature and upon dilution.

[Use of hydropyrite in the chemiluminescent determination of iron-porphyrin proteins].

Hydropyrite was found to be a suitable reagent which may be used in chemiluminescent reactions for determination of iron-porphyrin proteins.

[Radiometric study of the decarboxylating activity of desert soil microflora].

Employment of growth media containing salts of organic acids, labelled with 14C, gave a rapid and intensive signal concerning the decarboxylating activity of microorganisms from desert soils. The value of the signal was higher than that during the decomposition of uniformly labelled glucose. The results of these studies would help to select the optimal growth medium for carrying out exobiological experiments.