Chapter 15 : The Impact of Differential Regulation on Bacterial Speciation

Abstract:

The family Enterobacteriaceae, whose members are often referred to as the enterics, comprises several bacterial species that are known because of the diseases they cause in humans and/or in animals or plants of economic importance. This chapter presents four possible genetic scenarios to account for the differences that exist between the closely related bacterial species, Salmonella enterica and Escherichia coli. It also illustrates how variation in gene regulatory strategies can result in distinct bacterial behaviors. The comparative studies discussed in this chapter have revealed two distinct aspects that distinguish individual enteric species. First, organisms often vary in the environments in which the polymyxin B resistance proteins are produced, and this is often due to changes in the amino acid sequence of a regulatory protein. Second, two related organisms can synthesize the resistance proteins in response to the same signals but achieve dissimilar resistance levels as a consequence of the particular architecture that individual species utilize to promote expression of the resistance genes. The types of genetic differences that distinguish closely related species can be quite different depending on whether one is considering bacterial versus eukaryotic species.