Studying the molecular mechanisms of cold-adaptation of biological systems is intrinsically important to understand evolution and ecological interaction of species on Earth. In the Dry Valley region of Antarctica, a complete microbial ecosystem lives within sandstone at freezing temperatures and in permanently ice-covered lakes. Vestal proposes to determine whether psychrophilic phototrophs (cold-adapted cyanobacteria, algae, and photosynthetic bacteria) possess unique nucleotides and amino acids sequences in their DNA and a key CO2-fixing enzyme in photosynthesis to account for the enzyme's function at sub-zero temperatures. From a previous award (Small Grant for Exploratory Research), Vestal determined that this key enzyme from a psychrophilic cyanobacterium has unique photosynthetic properties that may be related to its molecular structure of this particular CO2-fixing enzyme. Using the latest methods of molecular biology, true psychrophilic phototrophs, which will be selectively isolated from sandstone and algal mats from Dry Valley lakes, will be studied. If these Antarctic psychrophiles possess unique sequences in their DNA and enzymes, the information would provide new insight into the mechanism of cold-adaptation of biological species and their evolutionary relatedness to other temperate species.