Mechanism of Catabolite Repression In The Archaeon Sulfolobus solfataricus

Sulfolobus solfataricus is an archaeon that thrives in a high temperature and low pH environment. Many Sulfolobus species have been isolated from terrestrial geothermal hot springs. In such places, the environmental factors greatly affect the temperature, pH, and availability of nutrients. To survive in such an environment, organisms must develop efficient strategies to obtain nutrients. Carbon catabolite repression (CCR) is a strategy to ensure optimal carbon metabolism. In this study, we employed Sulfolobus solfataricus as a model system to gain an understanding of the mechanisms of CCR in archaea. We isolated an S. solfataricus CCR mutant through screening of a lactose negative phenotype. Studies on this and related mutants showed that expression of lacS (beta-glycosidase) was reduced during growth in repressing media and by mutation of an unlinked locus called "car". The goal of this study was to identify key gene(s) or component(s) that control CCR in S. solfataricus. Extensive phenotypic study of CCR mutants revealed additional carbon metabolic defects associated with various sugars. In addition I found that the car mutation also resulted in changes in the expression level of several genes and proteins involved in chromatin remodeling, such as deacetylase and S-adenosylmethionine synthetase (metK). Genomic DNA library (BAC) screening and genome sequencing showed no apparent differences between the wild type and the car mutant. Taken together, my data show that the car mutation is pleiotropic and extragenic. To gain more insight into this phenomenon, chromatin DNA transformation and reconstitution experiments were conducted. The results revealed that the change in the chromatin dynamics affected the car CCR phenotype and that the CCR regulatory mechanism in S. solfataricus operates at the level of chromatin modification.