"cold adaptation in the extremely halophilic archaeon halorubrum lacusprofundi: a terrestrial model for extraterrestrial life" a key issue facing astrobiology is assessing what subset of…

"cold adaptation in the extremely halophilic archaeon halorubrum lacusprofundi: a terrestrial model for extraterrestrial life" a key issue facing astrobiology is assessing what subset of environments could be hospitable to life. Of particular interest are the temperature limits for species growth (habitable zone) and the adaptation strategies to thrive at those extreme temperatures. In the solar system and the galaxy as a whole, cold environments are much more common than hot environments. Mars-and europa, the prime solar system targets of searches for life beyond earth, present reldtively cold cavironments; however, both seem capable of supporting liquid water. At their best, martian conditions are not vastly dissimilar from cold regions of the terrestrial biosphere, such as the dry valleys of antarctica. Long regarded as essentially barren of life, considerable microbial activity has been recently found in these regions. Microbes that have adapted to extreme conditions are some of the best candidates for terrestrial analogues of potential extraterrestrial life: understanding their adaptive strategies and limitations will provide deeper insight on fundamental constraints on the range of habitable environments. The current project will study cold adaptation in the extremely halophiilic archaeon halorubrum lacusprofundi, isolated from deep lake, antarctica, whose genome is currently being sequenced. Its adaptation to cold temperatures and halophilicity render h. Lacusprofundi an excellent model organism to study the effect of extreme and potentially extraterrestrial conditions on life; i.e., there are strong indications that the water presumably present on mars is of high salinity. A further physiological hallmark of h. Lacusorofundi is the formation of multicellular assemblages, or biofilms. At cold temperatures. The formation of multicellular units is of supreme importance during evolution towards higher life forms. Cold adaptation in h. Lacusprofundi will be investigated using functional genomic, bioinformatic and biochemical approaches. A genomic comparison with related mesophilic and other cold-adapted archaea will identify key features required for adaptation to low temperatures. DNA microarrays will be designed and employed to record the expression levels of all genes of h. Lacusprofundi ring different temperature regimes. Genes thus idcntitied to be involved in cold adaptation will be overexpressed both in h. Lacusprofundi and in closely related non-cold adapted archaea. This will test whether the limits of cold adaptation can be expanded by higher cellular levels of those proteins. Adaptation on the protein level will be studied using beta-galactosidase from h. Lacusprofundi as a model enzyme. Comparisons with other beta-galactosidascs will aid in determining the underlying cause of protein cold-adaptation. Finally, the different stages in biofilm formation will be studied using DNA microarrays. Those analyses will identify genes that are important to achieve the tissue-like, functional compartmentalization of those multicellular units.