Characterization of a moderately halo-acidophilic bacterium isolated from Lake Brown, Western Australia

摘要

Compared to prevalent alkaline to neutral hypersaline environments, acidic hypersaline environments have been scarcely studied. However, they hold interest to many researchers in that these environments have similar geological and geochemical characteristics as those found in lithified strata on Mars. Fieldwork indicated that Lake Brown, located in Western Australia, possessed pH values of 3.1-4.5 and salinity between 13.0-23.0%. Water column, groundwater, and sediment samples were collected from the lake during the austral winter of 2005. These samples were analyzed with both traditional culture and molecular methods, Modified growth media and minimal media were designed to match the composition (Cl, Na, Mg, SO4, K, Ca, and Br) of Lake Brown surface and ground waters for the enrichment of microorganisms. One of the isolates obtained, Brown 1, can grow in media that possesses pH values of 3-7 with optimal growth at pH 4, salinity that ranged from 5% to saturation with optimal growth at 5% and could grow under temperatures that ranged from 20°C to 65°C with optimal grow occurring at 37°C. The isolate's optimum growth conditions are similar to those found in Lake Brown. The isolate is a Gram-negative rod that forms yellow colonies on 17% Phytogel. Its 16S rRNA gene can be amplified with bacterial primers but not with archaeal primers. Its 16S rRNA gene sequence suggests that the isolate is a gamma proteobacterium. Studies on organisms isolated from environments such as Lake Brown, an acid hypersaline lake, can provide an opportunity to both expand our knowledge of terrestrial extremophiles and gain insight on the possible forms of life that might have existed on Mars.