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Project Progress

One objective of the work was to test the proposal that all organisms placed phylogenetically at the base of the tree of life are thermophiles. The importance of this work is that the current picture of thermophiles being present as deep branching organisms has been used as evidence that the Last Common Ancestor was a thermophile and that the Earth environment was therefore hot. Another possibility is deep branching psychrophiles exist but have not been isolated. We have sampled a Greenland Ice Core and have turbid cultures in chemoautotrophic anaerobic media that has been incubated at 0 degrees C. We are attempting to increase the cell yield in order to extract sufficient DNA for PCR amplification to determine the types of microorganisms that are present. Independent of whether the organisms are deep branching the existence of these organisms are important for interpreting the geochemical analysis of the ice cores.

Another aspect of our work has been to isolate and characterize novel psychrophilic organisms as a basis for understanding how life might exist in other extreme environments. As part of this work, Dr. Sheridan has isolated several psychrophilic bacteria including a Planococcus species from a meltpond in Antarctica. He cloned and characterized a gene encoding a beta-galactosidase from this isolate. This gene is a member of the family 42 glycosyl hydrolases and produces a salt-tolerant beta-galactosidase that might be useful as a reporter gene in halophilic organisms. A manuscript describing this work will be published in the June 2000 issue of Applied and Environmental Microbiology. (A copy of the galley proofs is being sent separately.)