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Project Progress

Our research focuses on psychrophilic (cold-loving) microorganisms and their cold-active enzymes. This includes the analysis of psychrophiles from cold environments including the subseafloor, Antarctica, lakes, and cold soils. One project designed for PSARC investigates microorganisms deposited over 100,000 years ago in the basal portion of a Greenland glacier (GISP2) ice core. Research with this ice core serves as a model for severe conditions, such as cold temperatures, nutrient and oxygen limitations, desiccation, pressure, etc. that could exist extraterrestrially. Our current PSARC goals include: Determining microbial diversity in the ice core, 2) Examining the ultra-small cells and their viability and 3) Testing factors that affect the survival and culturability of the ice core microbes.

Our investigation demonstrated the presence of an abundant viable (10⁷ cells/ml) microbial population trapped in the ice core and the existence of many ultra-small cells. Dr. Miteva examined ultra-small cells in cultures inoculated with samples repeatedly filtered to exclude larger cells and demonstrated that many pass through filters with pore sizes as small as 0.2, and even 0.1, microns. Growth studies demonstrated that some isolates retain their small cell size throughout their growth cycles in different media suggesting that they are intrinsically small. Phylogenetic comparisons of the 16S rRNA gene sequences showed a wide diversity of bacterial isolates including some that may represent new genera and species. Our results show that numerous viable ultra-small cells are present in the ice core sample and that filtration and long-term incubations significantly increase the number and diversity of colonies. The ultra-small cells compose a large fraction of the uncultivated microorganisms in many environments, and thus, our results are relevant to other studies where samples were filtered and only the cells trapped on filters examined or where short incubations were used to recover colonies.