Physiological studies on Sulfolobus solfataricus strain 98/2 and its glycosyl hydrolases

Sulfolobus solfataricus is a hyperthermoacidophilic microorganism belonging to the Archaea domain. The basal transcriptional system present in the Archaea resembles the machinery present in Eukaryotes. However, little is known about how genes are regulated in this domain. The purpose of this work was to study the catabolite repression-like mechanism occurring in the Archaea using S. solfataricus as a model. To achieve this goal, a set of enzymes involved in metabolism were selected ( malA, lacS, α-amylase, and gdh) and then their levels were determined as a consequence of enrichment of a minimal medium. The results presented in this dissertation reveal the presence of a global regulatory mechanism operating in this archaeon. The system seems to respond only to the quality of the carbon source present in the media. The global regulatory system studied seems to act at the level of transcription and, in that regard, it resembles the catabolite repression systems already described for members of the other domains. The system seems to be acting in trans considering the fact that at least two physically unlinked genes (lacS and malA) are affected at the level of transcription. The isolation of mutants also supports a trans acting system. Based on the results obtained, a catabolite repression system is proposed (CRI) which, under uninduced conditions, regulates the activity of these physically unlinked glycosyl hydrolases at the level of transcription. Hyperthermophilic proteins are potential for uses in different aspects of biotechnology. The work presented in this dissertation also concerns the production of transgenic tobacco plants containing hyperthermostable glycosyl hydrolases from S. solfataricus to test the possibility of triggering plant tissue auto digestion following activation of recombinant enzymes by heating. The recombinant expression and activity of these enzymes on plant tissue was demonstrated. Additional experiments showed that the combination of extracts from α-glucosidase and β-glycosidase producing plants increased the glucose released and yields synergistically. The action of both enzymes at the same time allows a more efficient and cooperative plant polysaccharide degradation