Master's Thesis Defense: Victoria Laye, MEES

May 3, 2018 11:00am to 12:00pm iCal Google Calendar

Title: "Survival of a Polyextremophilic Archaeon and Function of Its Enzyme in Potentially Astrobiological

Speaker: Victoria Laye, Master's Candidate, MEES

Abstract: Haloarchaea are extremophilic microorganisms that can be used as models for how life can survive in niche environments on Earth and other planets thought to be inhospitable, like Mars. They are able to survive multiple extreme conditions like high salinity, cold temperatures, desiccation, and UV radiation. We compared Halorubrum lacusprofundi, a cold-adapted isolate from the Vestfold Hills of Antarctica with Halobacterium sp. NRC-1, a mesophilic laboratory strain for growth in the presence of potentially toxic magnesium and perchlorate ions. Both haloarchaea were able to tolerate concentrations higher than those expected on Mars, with greater inhibition by perchlorate than magnesium. These haloarchaea have also been exposed to stratospheric conditions and shown to tolerate such conditions as freeze-thaw and radiation. H. lacusprofundi has a better survival rate than Halobacterium sp. NRC-1 after freeze-thaw as expected from its psychrophilic nature.
A cold-active β-galactosidase enzyme from H. lacusprofundi was used as a model protein to establish the capability of the enzyme to function in the presence of magnesium and perchlorate and in cold temperatures. The enzyme was determined to be more inhibited by magnesium than perchlorate. The cold-activity of the enzyme was also investigated in detail through the use of bioinformatics, genomics, and mutagenesis by identifying a small number of divergent amino acids and creating single amino acid mutations. Mutated enzymes were tested using steady-state kinetics and determined to be less cold-active than the wild-type, confirming the importance of the residues for improved activity at cold temperatures. H. lacusprofundi and its enzyme are able to tolerate both toxic ions and extreme cold, making them ideal models for better understanding mechanisms of adaptation of life in polyextreme environments on Earth and potentially other planets.

Host: Dr. Shiladitya DasSarma