Lipid biomarkers from microbial mats on the McMurdo Ice Shelf, Antarctica: signatures for life in the cryosphere

Persistent cold temperatures, nutrient limitations, freeze-thaw cycles, and variable light regimes make Antarctica one of Earth's least hosptiable environments for complex life. Cyanobacteria, however, are well-adapted to such extreme conditions and are often the doimant primary producers in Antarctic freshwater environments. In particular, the network of meltwater pnods on the "dirty ice" of the McMurdo Ice Shelf is an ecosystem in Antarctica that has extensive cyanobacteria-dominated microbial mat biomass accumulations. This study investigated the composition of microbial communities in twelve meltwater ponds by analysis of 16S and 18S rRNA gene sequences as well as intact polar lipids, heterocyst glycolipids, and bacteriohopanepolyols to evaluate lipid composition in microbial mats growing in permanently low temperature and nutrient limited environments.