Adaptation by phase variation in pathogenic bacteria.

Publisher Summary This chapter focuses on the transitions that are facilitated by the switching of phase-variable genes, thereby focusing on pathogenic bacteria. The ability to adapt to changing environments is essential for the survival, development, and evolution of bacterial species. Often, this takes the form of programmed responses to environmental stimuli. Such adaptability can also be generated through diversity within the population, which serves to increase the chances of survival of a portion of the population if not the whole. Although diversity mediated by mutational processes is at times generated randomly, some species have developed a means of programming which genes will undergo mutations, within hypermutable loci and, through this mechanism, generate frequent and reversible changes in phenotypes that result in a mixed population. The process is referred to as “phase variation” and involves predictable and predetermined changes in the structure of the bacterial DNA mediating the reversible expression of phenotypes that confer adaptive advantage in various environments.