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Gene regulation in the hyperthermophilic crenarchaeote Sulfolobus solfataricus
Abstract
Sulfolobus solfataricus is a hyperthermophilic thermoacidophile that is phylogenetically classified using rDNA sequence comparisons as a member of the crenarchaeotal branch of the archaea. This obligately aerobic prokaryotic organism is capable of chemoheterotrophic growth on a variety of carbon and energy sources. The control of production of three glycosyl hydrolases was chosen as a model for. the study of gene regulation in S. solfataricus . The work described here examines regulation of glycosyl hydrolase production in response to carbon source and represents the first report of a catabolite repression-like system in a crenarchaeote. The major secreted α-amylase was purified and is a homodimer with an apparent subunit mass of 120 kDa. Enzyme production is sensitive to the presence of specific carbohydrates. Rich medium and glucose prevent α-amylase production in the presence of starch while glutamate acts as a nonrepressing carbon source. A hierarchy of carbon sources was observed with respect to enzyme production that ranked their repressing nature in the absence of starch. A global gene regulatory system is in place in S. solfataricus . Production of both the α-glucosidase and β-glycosidase are reduced in the presence of rich medium. Control is at the mRNA level as transcripts from the unlinked structural genes vary in response to carbon source. Transcriptional induction of the lacS gene (β-glycosidase encoding) following removal of rich medium is rapid and occurs within one generation. Transcript removal is 35 fold slower, however, and the lacS transcript appears to be unusually stable. A trans-acting factor is involved in glycosyl hydrolase control. Characterization of glycosyl hydrolase mutants identified two distinct classes: complete lacS deletion and pleiotropically defective (Car) mutants. Car mutants are defective for both α-amylase and β-glycosidase activities. Reduced mRNA abundance is responsible for diminished β-glycosidase activity. A lack of genomic alterations indicates a trans-acting mutation affecting two unlinked genes. Unselected revertants are partially restored for α-amylase and β-glycosidase activities. These results indicate the presence of a catabolite repression-like trans-acting gene regulatory system in S. solfataricus.
Subject Area
Microbiology
Recommended Citation
Haseltine, Cynthia Ann, "Gene regulation in the hyperthermophilic crenarchaeote Sulfolobus solfataricus" (1999). ETD collection for University of Nebraska-Lincoln. AAI9951293.
https://digitalcommons.unl.edu/dissertations/AAI9951293