Valerie Stout
Research
In general, my research interests are in environmentally-responsive regulation. The primary focus of my lab is to examine the regulation of colanic acid polysaccharide capsule synthesis in Escherichia coli. This polysaccharide serves as a common antigen among most members of the Enterobacteriaceae family. The level of synthesis of colanic acid can be induced more than 100- fold depending on the environmental conditions and the genetic background. Because it is induced at low temperatures and is comprised of 99% water, this capsule may play the pivotal pathogenic role of enhancing survival and facilitating the spread of E. coli from one host to another by preventing dessication. In addition, the synthesis of colanic acid in E. coli seems to share some common regulatory features with the synthesis of capsules from other bacteria in which the capsule functions as a critical virulence factor.
Colanic acid synthesis in E. coli is under the transcriptional control of several regulators. The goal of this lab is to understand the functions of these four regulators using genetic, biochemical and molecular biology techniques. Two of the regulators belong to a large family of two- component regulatory pairs found in a variety of microorganisms that respond to environmental signals. Current studies are concerned with analyzing the interaction of these two proteins with each other and with the two other regulatory proteins and the target DNA. In addition to these in vitro studies, genetic mutation of the regulators should provide more information about their functions.
In addition to the work on the E. coli capsule, I plan to begin examining the regulation of capsule synthesis and other important environmentally-responsive virulence factors in the pathogenic organism, Staphylococcus aureus. The problem will be approached by initially performing a genetic selection for avirulent (unencapsulated) mutants, followed by biochemical and molecular genetic characterization of these mutants and their wild type counterpart genes.
Selected Publications
Stout V., Hanna A., Berg M., and Razatos A. (2003). Role of capsular colanic acid in adhesion of uropathogenic Escherichia coli. Applied and Environmental Microbiology 69: 4474-4481.
Stout V., McVicker L., and Duffy D. (1998). Microbial growth in a steady-state model of ethylene glycol-contaminated soil. Current Microbiology 36: 136-147.
Stout V., Gupte G., and Woodward C. (1997).Isolation and characterization of rcsB mutations that affect colanic acid capsule synthesis in Escherichia coli K-12. Journal of Bacteriology 179: 4328-4335.
Stout V., and LopezTorres A.J. (1996). Role of colanic acid polysaccharide in serum resistance in vivo and in adherence. Current Microbiology 33: 383-389.
Stout V. (1996). Identification of the promoter region for the colanic acid polysaccharide biosynthetic genes in Escherichia coli K-12. Journal of Bacteriology 178: 4273-4280.
Stout, V., (1994). Regulationof Capsule Synthesis Includes Interactionsof the RcsC/RcsB Regulatory Pair. Res. Microbiol. 145, 389-392.
Gottesman, S. and Stout, V. (1991). Regulation of Capsular Polysaccharide Synthesis in Escherichia coli K-12. Molecular Microbiology. 5:1599-1606
Stout, V., Torres-Cabassa, A., Gutnick, D., Maurizi, M., and Gottesman, S. (1991). RcsA, An Unstable Positive Regulator of Capsular Polysaccharide Synthesis. J. Bacteriol. 173: 1738-1747.
Stout, V. and J.J. Iandolo (1990) Chromosomal gene transfer during conjugation by Staphylococcus aureus is mediated by transposon-facilitated mobilization. J. Bacteriol. 172:6148- 6150.
Stout, V. and Gottesman, S. (1990) RcsB and RcsC: a Two-Component Regulator of Capsule Synthesis in Escherichia coli. J. Bacteriol. 172: 659-669.