Boreskov

SURVIVAL OF HALOPHILES AT DIFFERENT SALT CONCENTRATIONS ANDFREEZING CYCLESBryanskaya A.V. 1 , Berezhnoy A.A. 2 , Rozanov A.S. 1 , Peltek S.E. 1 , Pavlov A.K. 31 Institute of Cytology and Genetics, SB RAS, Novosibirsk, Russia2 Sternberg Astronomical Institute, Moscow State University, Russia3 Ioffe Physical‐Technical Institute, St. Petersburg, RussiaPP‐46Earth’s microorganisms can be delivered to Mars by impacts of meteoroids of Earth’sorigin and modern mission to Mars. To study of the possibility of survival of Earth’smicroorganisms on Mars, we need to select the most suitable types of them. Halophiles areone of the most interesting types of microorganisms, because salt solutions on Mars couldbe more widely distributed through subsurface martian soil in comparison with pure liquidwater. The existence of salt solutions that could serve as media for organisms analogous tohalophilic archea at ‐23 °C and high salt concentrations on Mars has been widely discussed[1]. Study of the elemental composition of the Martian soils shows high concentrations of Cl[2], perchlorates, and solubable sulfates [3].The aim of this study was to select bacterial and archeal strains most adapted to Martianconditions for the next step of our experiment about the possibility of the active growth ofthese microorganisms at dryness, low atmospheric pressure and other extreme conditions.Methods. Bacterial (Halomonas sp. H‐8, Halomonas sp. H‐12, Salicola sp. H‐9) andarcheal (Halorubrum sp. H‐2, Halorubrum sp. H‐3, Halorubrum sp. H‐4, Halorubrum sp. H‐7,Halorubrum sp. H‐11, Halorubrum sp. H‐13) strains were isolated from different salt lakes ofAltay region. Strains were grown in medium, which contained per liter 0‐300 g NaCl, 5 gMgCl 2 , 1 g KCl, 1 g CaCl 2 , 4 g tryptone, 2 g yeast extract, and 10 ml of a trace metal solution,at 37 o C. For exposure experiments cells were suspended in a medium with the same NaClconcentration. Following treatments, cells were plated on solidified growth medium andincubated at 37 o C for several days. Cell numbers were estimated from CFU. Treatments wereas follows: aliquots of cell suspensions were kept both at – 70 o C and ‐ 18 o C for up to sevendays. At least three exposure experiments were performed.Results. Halomonas sp. H12 strain had the widest growth range (50‐300 g L ‐1 ) andoptimum at 100 g L ‐1 NaCl. Other strains grew at 100‐300 g L ‐1 and had the growth optimumat 100 and 200 g L ‐1 (Halomonas sp. Н8, Salicola sp. Н9); and Halorubrum strains Н2, Н3, Н4,Н7, Н11, Н13, at 200 and 300 g L ‐1 . Freezing of cultures at ‐70 °C и ‐18 °C for 168 hoursusually resulted in reduction of CFU. At 100 g L ‐1 NaCl and after freezing at ‐70 °C and ‐18 °C,217