RUI: Function of LacI-type Transcription Factors in Caulobacter

Santa Clara University, Santa Clara CA

Investigators

Abstract

The genome of the Gram-negative aquatic bacterium Caulobacter crescentus encodes numerous enzymes for extracellular breakdown of plant-derived polysaccharides such as cellulose, xylan, arabinogalactans, and pectin. Both Caulobacter crescentus and a closely related groundwater species, Caulobacter strain K31, avidly consume D-glucose and D-xylose, the monosaccharide constituents of cellulose and xylan, as carbon and energy sources. A LacI-type repressor, XylR, controls the expression of genes involved in uptake and degradation of D-xylose, and there is evidence to suggest that another LacI homolog ('GlcR') controls glucose uptake and metabolism. This project will explore the regulatory and physiological functions of XylR and GlcR in greater depth, and extend these studies to the remaining 10 members of the LacI family encoded in the C. crescentus genome, which are hypothesized to also regulate expression of extracellular hydrolases, transport systems, and metabolic pathways for consumption of various sugars and other organic molecules. Each LacI homolog will be knocked out, and comprehensive gene expression profiles will be obtained through microarray technology to characterize gene sets controlled by each transcription factor. This project will provide the first comprehensive view of the physiological roles of the LacI-type transcription factors in the biology of a single organism, thereby expanding our understanding of the function and evolution of the LacI family of transcription factors, which is ancient and widespread in bacteria. The role of LacI homologs in controlling extracellular degradation of biopolymers such as cellulose and xylan makes them of great interest for enhancing biofuels production. The project will also provide insight into regulation and coordination of carbon transport and metabolism, which is fundamentally relevant to growth and niche colonization in bacteria. From an educational and human resource perspective, this project will have tremendous impact by providing 20-40 undergraduates with research and educational opportunities through multi-year projects for two research-intensive courses, Bio 176 Recombinant DNA Technology, and Bio 178 Gene Expression Analysis. These courses are an integral part of the Biotechnology Program at Santa Clara University, through which students learn sophisticated microbiological, molecular biological, and biochemical techniques, and explore the social ramifications of biotechnology. Development of technical skills, and more generally development of critical thinking and scientific thought processes, prepares these students to undertake skilled positions in life sciences research and related fields after graduation. In supporting these courses, this RUI grant strongly aids the broader educational mission of Santa Clara University, an undergraduate-focused institution.