Are humans increasing bacterial evolvability?

By Michaal R Gillings and HW Stokes

In Trends in Ecology and Evolution

Volume 27, Issue 6, June 2012, Pages 346-352 (not open access)

Abstract:  Attempts to control bacterial pathogens have led to an increase in antibiotic-resistant cells and the genetic elements that confer resistance phenotypes. These cells and genes are disseminated simultaneously with the original selective agents via human waste streams. This might lead to a second, unintended consequence of antimicrobial therapy; an increase in the evolvability of all bacterial cells. The genetic variation upon which natural selection acts is a consequence of mutation, recombination and lateral gene transfer (LGT). These processes are under selection, balancing genomic integrity against the advantages accrued by genetic innovation. Saturation of the environment with selective agents might cause directional selection for higher rates of mutation, recombination and LGT, producing unpredictable consequences for humans and the biosphere.

Figure 1. How antimicrobial agents affect both short- and long-term evolvability in Bacteria. (a) Mechanisms that generate genetic diversity, such as rates of mutation, recombination and lateral gene transfer (LGT) exhibit variation among members of a population. (b) Short-term exposure to an antimicrobial agent causes transient increases in these rates for each individual cell (dotted line), through mechanisms such as induction of the SOS response. (c) Selection for lineages with inherently higher rates of generation of genetic diversity results in long-term changes in the basal rates of mutation, recombination and LGT in subsequent generations (dashed line).