Relics of selection in the mycobacterial genome

Abstract

A new study reports the whole-genome sequences of 21 Mycobacterium tuberculosis complex strains, selected to represent geographically diverse isolates. Comparative genomic analyses identify surprising conservation of epitopes recognized by human T cells.

Figure 1

The population dynamics of Mycobacterium tuberculosis are influenced by immune-related selection during growth within a host. An individual human is infected by a single bacterium (or small group of bacteria), and growth within the human host may bring some diversity in the mycobacterial population. (a) In the absence of selection, each clone has an equal likelihood of transmission to a new host. (b) If the immune system recognizes early clones and destroys them, variant strains will have an advantage and outgrow the original strains. (c) Alternatively, strains with specific epitopes might generate an inflammatory response that increases their probability of transmission.