Gene expression in E.coli K-12 MC4100 at 37˚C and 23˚C in M9 glycerol exponential phase growth

Because many virulence genes in E. coli and other pathogens are regulated by temperature, we wanted to determine on a genome-wide scale which genes are modulated in adapting to both human host temperature (37˚C) and ambient room temperature (23˚C). Overall, 126 genes were found to be more highly expressed at 37˚C (1) whereas 297 genes were more highly expressed at 23˚C (2). Genes involved in the uptake and utilization of amino acids, carbohydrates, and iron dominated the 37˚C list, supporting a model in which temperature serves as a host cue to increase expression of bacterial genes needed for growth. 122 of the 297 genes more highly expressed at 23˚C are RpoS-controlled, confirming genome-wide the model that low temperature serves as a primary cue to trigger the general stress response. Several genes expressed at 23˚C overlap with the cold shock response, suggesting that strategies used to adapt to sudden shifts in temperature also mediate long-term growth at 23˚C. Another category of genes more highly expressed at 23˚C are associated with biofilm development, implicating temperature as an important cue influencing this developmental pathway. 1.) White-Ziegler, C. A., A. J. Malhowski, and S. D. Young. Human body temperature (37˚C) increases the expression of iron, carbohydrate, and amino acid utilization genes in Escherichia coli K-12. Journal of Bacteriology 2007. Vol. 189(15):5429-40. Epub 2007 May 25. 2.)White-Ziegler, C. A., S. Um, N.Peréz, A. L. Berns, A. J. Malhowski, and S. Young. Biofilm, coldshock, and RpoS-dependent genes demonstrate increased expression during low temperature growth (23˚C) in Escherichia coli K-12. In revision for Microbiology. Keywords: stress response Growth and medium conditions were chosen (M9 glycerol medium with aeration) that maximize papBA transcription at 37˚C so we could use this operon as a temperature-regulated positive control in our microarrays. Parallel cultures grown at 37˚C and 23˚C were harvested in exponential phase (OD600=0.2-0.6) at 9-11 generations growth after inoculation. Thus, the results presented here reflect the adapted state and signify genes whose expression is differentially maintained over long-term growth at a given temperature. 1.) White-Ziegler, C. A., A. J. Malhowski, and S. D. Young. Human body temperature (37˚C) increases the expression of iron, carbohydrate, and amino acid utilization genes in Escherichia coli K-12. Journal of Bacteriology 2007. Vol. 189(15):5429-40. Epub 2007 May 25.