ABSTRACT
The ability to profile global changes in the levels of gene expression under different conditions makes microarrays the method of choice in many areas of modern biology. They have been used to study differential gene expression in different growth conditions, for example Escherichia coli grown in minimal versus rich media (Tao et al., 1999) and glucose versus acetate as the sole carbon source (Oh et al., 2002). In addition, changes in response to chemical exposure or environmental stress have also been investigated; for example, the response of E. coli to hydrogen peroxide (Zheng et al., 2001) and to UV light (Courcelle et al., 2001). An alternative approach is to compare expression profiles between wild type and mutant stains. Gene expression profiling of E. coli mutants defective in IHF (Arfin et al., 2000) and H-NS (Hommais et al., 2001), have identified genes that are either positively or negatively regulated in the absence of these transcription factors.
