Chapter 7 : Part II Overview

Abstract:

This section provides an overview of five chapters that discuss the general principles of pathogen evolution (chapters 8 and 9) and the mechanisms by which specific bacterial virulence determinants may have evolved (chapters 10, 11, and 12). The discussion on environmental settings that provided selection pressures for the evolution of certain virulence determinants focuses on soil (chapter 8) and the human gut (chapter 9). To begin to analyze complicated and dynamic microbial communities and how they contribute to health and disease will certainly necessitate the development of approaches quite different from those developed to specifically focus on bacterial pathogenesis. While the first two chapters focus on the selective pressures that drive the evolution of factors that can contribute to disease, the third chapter focuses on the mechanistic question of how one class of bacterial virulence determinants (exotoxins) evolved and moved between different microbial species. There are several systems that microbes utilize to solve the problem of translocating macromolecules across their two membranes. Apart from acquisition of antibiotic resistance mechanisms by horizontal gene transfer, the authors describe the rise of antibiotic-resistant strains by mutation. The frequency with which strains with increased rates of mutation are isolated upon challenge with antibiotics is also discussed.