UC San Diego

Life in the deep sea presents organisms with a number of challenges that must be overcome through evolutionary adaptation. The most unique of these challenges is that of high hydrostatic pressure. This stress has the potential to affect a number of processes inside the cell and poses a thermodynamic constraint on reactions that involve changes in volume. A number of piezophilic adaptations have been found and more are reported in this thesis. One such adaptation that has been previously explored is that of sequence insertions in the 16S ribosomal RNA. Here, the rest of the ribosome is analyzed and it is found that the 23S ribosomal RNA also has piezophilic-specific insertions. Mutations are also found in some ribosomal proteins and strong evidence is found for ribosomal RNA operon recombination in Photobacterium profundum SS9. The volume change constraint was explored directly using a method that predicts protein folding volume. Applied to pairs of piezophiles and mesophiles, trends in folding volume for select proteins were examined. It was concluded that the method could be useful, but further changes to the algorithm are necessary before conclusions can be drawn. Lastly, the genome of Moritella sp. PE36 has been sequenced and partially closed. Analysis of the draft genome annotation reveals increased proportions of genes encoding proteins involved in cell motility, metabolism, and secretion relative to that present in related non- piezophilic bacteria. This last gene product category increase is likely to support the surprisingly high number of proteins predicted to have signal peptides