Christine A. White-Ziegler

Associate Professor of Biological Sciences, Smith College

C. White-Ziegler Biology Dept Website

Ph.D.: University of Utah
Postdoctoral Training: University of Utah

Environmental Regulation of Gene Expression in Escherichia coli

The research in my lab is aimed at studying how a bacterium senses its environment and uses environmental cues to control gene expression. Bacteria are able to sense a variety of environmental stimuli such as temperature, pH, osmolarity, and oxygen levels. Bacteria are able to use this information and subsequently regulate gene expression based on their surroundings. This is particularly true among bacterial pathogens in which the expression of virulence factors, such as toxins, adhesins, and pili, is often regulated in response to the environment.

To study environmental regulation of gene expression in Escherichia coli, we have been studying the effect of temperature on the expression of pyelonephritis-associated pili (P pili). P pili are hairlike appendages that project from the surface of the bacterium, bind to epithelial cells, and facilitate colonization of the urogenital tract. Whereas P pili can be expressed at 37ƒC, the expression of these pili are turned off in response to low temperature (23ƒC). We have taken a genetic approach to isolating and characterizing mutants that can transcribe the pilus genes at low temperature, thereby identifying genes involved in the temperature regulation of P pili production. Mutations in two genes, rimJ and hns, have been shown to disrupt the thermoregulation of P pili expression.

Current work in my lab is aimed at investigating the roles of the RimJ and H-NS proteins in the environmental regulation of gene expression in E. coli. The role of H-NS and RimJ in controlling transcription of other pili operons in E. coli is being investigated using a variety of genetic and molecular biology techniques. We have also designed a genetic screen to identify other genes in E. coli that are controlled by RimJ. Through these experiments, we hope to determine if RimJ and H-NS form part of a global regulatory network that regulates virulence genes, as well as other genes, in response to the environment.

Representative publications:

White-Ziegler, Christine A. , Alia M. Black, Stacie H. Eliades**, Sarah Young**, and Kimberly Porter**. 2002. The N-acetyltransferase RimJ responds to environmental stimuli to repress pap fimbrial transcription in Escherichi coli . Journal of Bacteriology. Vol. 184, pp. 4334-4342.

White-Ziegler, Christine A. , Anuradha Villapakkam**, Karla Ronaszeki**, and Sarah Young**. 2000. H-NS controls pap and daa fimbrial transcription in Escherichi coli in response to multiple environmental cues. Journal of Bacteriology. Vol. 182, pp. 6391-6400.

White-Ziegler, C.A., Angus Hill, M.L., Braaten, B.A., van der Woude, M.W. and Low, D.A. (1998) Thermoregulation of Escherichia coli pap transcription: H-NS is a temperature-dependent DNA methylation blocking factor. Mol. Microbiol. 28, 1121-1137.

White-Ziegler, C.A. and Low, D.A. (1992) Thermoregulation of the pap operon: evidence for the involvement of RimJ, the N-Terminal acetylase of ribosomal protein S5. J. Bacteriol. 174, 7003-7012.

White-Ziegler, C.A., Blyn, L.B., Braaten, B.A. and Low, D.A. (1990) Identification of an Escherichia coli genetic locus involved in thermoregulation of the pap operon. J. Bacteriol. 172, 1775-1782.