title: Multiplication of certain soil micro-organisms under simulated Martian conditions.
abstract: According to earlier observations, severe UV irradiation kills all micro-organisms in a chamber with simulated Martian conditions. However, even a thin soil layer protects buried micro-organisms from UV irradiation. The chief limiting factor for microbial multiplication under simulated Martian conditions seems to be soil humidity. Several micro-organisms were isolated from harsh environments (e.g., from Arctic, Antarctic desert and high-mountain soil samples). A strain of an oligonitrophilic mycococcus, isolated from Dixon Island, proved to be most resistant to low humidity. It multiplied in a mixture of limonite (maximal hygroscopical humidity 3.8%) + 2% (w/w) garden soil kept in a chamber simulating Martian conditions. Total cell count increased 7.6-fold and, in some experiments, 26-fold in 14 days. The oligonitrophilic mycococcus was able to grow even at a humidity level of 2.5%, that is less than maximal hygroscopical (3.8%). Under these conditions cell count increased 10-fold in 36 days. Thus, it was shown that even in Earth soils there are xerophytic micro-organisms which are able to multiply in limonite of low humidity. These data might correct our current concepts concerning microbial water requirements. One might speculate that Martian micro-organisms belong to xerophytic species.
authors.affiliation: Academy of Sciences, Moscow, USSR.
authors.forename: A A
authors.initials: AA
authors.lastname: Imshenetsky
authors.forename: L A
authors.initials: LA
authors.lastname: Kusjurina
authors.forename: V M
authors.initials: VM
authors.lastname: Jakshina
mesh_terms: D000192:Actinomycetales / Q000254:growth & development; D001407:Bacillus / Q000254:growth & development; D003081:Cold Climate; D003889:Desert Climate; D018559:Exobiology; D005290:Ferric Compounds; D006813:Humidity; D018535:Mars; D008837:Micrococcus / Q000254:growth & development; D012231:Rhizobium / Q000254:growth & development; D012988:Soil Microbiology
chemical_list: D005290:Ferric Compounds; C021024:ferric hydroxide