Rates of Lateral Gene Transfer in Prokaryotes: High but Why?

Lateral gene transfer is of fundamental importance to the evolution of prokaryote genomes and has important practical consequences, as evidenced by the rapid dissemination of antibiotic resistance and virulence determinants. Relatively little effort has so far been devoted to explicitly quantifying the rate at which accessory genes are taken up and lost, but it is possible that the combined rate of lateral gene transfer and gene loss is higher than that of point mutation. What evolutionary forces underlie the rate of lateral gene transfer are not well understood. We here use theory developed to explain the evolution of mutation rates to address this question and explore its consequences for the study of prokaryote evolution.

TrendsThe rate of lateral gene transfer (LGT) in prokaryotes can be high, and is likely to have profound consequences for genome evolution and adaptation. However, the selective forces underlying LGT rates have remained relatively unexplored. Insights from theory developed to explain the evolution of mutation rates can be applied to the evolution of LGT rates.We identify two main scenarios that could explain the high observed rates of LGT. In the first scenario, LGT rate is optimal while in the second scenario the rate of LGT is suboptimal.The diverse mechanisms and fitness effects of LGT events make it challenging to address evolutionary costs and benefits. A combination of population genomic and experimental approaches will be needed to establish LGT rates and the distribution of fitness effects of LGT events.