[Survival of bacteria in the Artificial Mars unit]. / Vyzhivaemost' bakterii v ustanovke "Iskusstvennyi Mars".

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. It has been concluded that microorganisms quite different in their physiological requirements and ecological properties can exist in the habitats extreme for life conditions.

[Use of a method of concentrating microorganisms in an electric field in the search for life in Mars]. / Primenenie metoda kontsentrirovaniia mikrooranizmov v élektricheskom pole dlia poiskov zhizni na Marse.

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 0.5 ml/min. A high concentration of microorganisms in a suspension can be reached when the current is switched off and a small volume of the fresh nutrient medium is passed through the suspension.

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 1.5-2.0% were isolated. None of the 40 strains of microorganisms studied, all belonging to different systematic and physiological groups, exhibited growth inhibition on solid media in the presence of Martian soil analogues. In view of the fact that Martian soil cannot contain microorganisms in great quantities, we suggest using electroadsorption for their concentration, to make detection reliable. A device was designed for this purpose, using the principle of electroadsorption on a polarisable carrier (sterile cotton wool or cheesecloth). The concentrated suspension of microorganisms thus obtained was then characterized by various physicochemical methods.

[Search for life on Mars]. / O poiskakh zhizni na Marse.

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]. / Vliianie perekisi vodoroda i gidratirovannykh okislov zheleza na metabolizm pochvennoi mikroflory.

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. Limonite stimulates the metabolic activity of microrganisms. The cultural and morphological properties of microflora are described, which are typical of soils incubated in the presence of limonite and hydrogen peroxide. This work supports the conclusion that, theoretically, the ground of Mars may contain microorganisms which have adapted, in the course of evolution, to high concentrations of hydrogen peroxide and hydrated iron oxides (of the limonite type) in the surrounding medium.

[Possibility of the nonbiological binding of CO2 and CO by the components of Martian soil]. / O vozmozhnosti nebiologicheskogo sviazyvaniia CO2 i CO komponentami marsianskogo grunta.

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]. / Opredelenie uglekisloty, vydeliaiushcheisia iz pochvy pri razlichnoi ee vlazhnosti.

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]. / Gazokhromatograficheskoe issledovanie zhidkikh kul'tur mikroorganiz-mov kak metod obnaruzheniia zhizni vne Zemli.

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. This method is a dynamical one, and can be employed to control the activity of microorganisms.

[Origin of the oxygen detected by the Viking stations in an analysis of Mars soil]. / O proiskhozhdenii kisloroda, obnaruzhennogo stantsiiami Viking pri analize grunta Marsa.

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. Apparently, the ground of Mars contains not only hydrated iron oxides but also frozen hydrogen peroxide whose thawing in the incubation chamber of Viking resulted in its catalytic degradation under the action of iron ions. The evidence thus obtained and its comparison with the data of American scientists account for considerable evolution of oxygen detected by Viking upon analysis of the Mars ground.

[Optimal conditions for determing ATP of microbial origin]. / Optimal'nye usloviia opredeleniia ATF mikrobnogo proiskhozhdeniia.

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. The activity of luciferin-luciferse solutions did not change after freezing in liquid nitrogen with following thawing. The content of ATP was assayed in the cells of Sarcina flava disintegrated with ultrasound.

[Use of hydropyrite in the chemiluminescent determination of iron-porphyrin proteins]. / Primenenie gidropirita v reaktsiiakh khemiliuminestsentnogo opredeleniia zhelezoporfirinovykh belkov

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]. / Issledovani dekarboksiliruiushchei aktivnosti mikroflory pustynnykh pochv radiometricheskim metodom

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.