Generators of Phenotypic Diversity in the Evolution of Pathogenic Microorganisms

All organisms run the gauntlet of Darwinian selection. Poignant examples include microbial pathogens, which must survive and thrive in their hosts. The process of pathogen adaptation to the host is diverse and is now known to involve a panoply of diversity generators, such as sexual/parasexual reproduction, aneuploidy, prions, mutators, telomeric silencing/recombination, and Hsp90 as a capacitor for evolution [1], [2] (Figure 1). Given the vast diversity of known mechanisms that can generate phenotypic and genotypic assortments, others likely remain to be discovered. Open in a separate window Figure 1 Generators of phenotypic diversity illustrated as a game of chance. Evolution is a multifactorial process that depends on numerous complex factors, including routes to diversity that can be deleterious, neutral, or advantageous depending on the environment. Here we depict these evolutionary trajectories using the analogy of a roulette wheel in which one possible path yields a winner that develops a new trait that allows the microorganism to survive in novel conditions, such as a host treated with antimicrobial agents. However, as in roulette, the odds are against the gambler and the other routes and outcomes are deleterious.