Sampling the mobile gene pool: innovation via horizontal gene transfer in bacteria

Abstract

In biological systems, evolutionary innovations can spread not only from parent to offspring (i.e. vertical transmission), but also 'horizontally' between individuals, who may or may not be related. Nowhere is this more apparent than in bacteria, where novel ecological traits can spread rapidly within and between species through horizontal gene transfer (HGT). This important evolutionary process is predominantly a by-product of the infectious spread of mobile genetic elements (MGEs). We will discuss the ecological conditions that favour the spread of traits by HGT, the evolutionary and social consequences of sharing traits, and how HGT is shaped by inherent conflicts between bacteria and MGEs.This article is part of the themed issue 'Process and pattern in innovations from cells to societies'.

Keywords: accessory genome; horizontal gene transfer; lateral gene transfer; pan-genome.

Figure 1.

The many routes for horizontal gene transfer. DNA can be transferred between individuals by multiple mechanisms falling broadly into three categories. In transduction (blue text), DNA is transferred either as part of the phage genome itself or as additional DNA packaged into phage particles or gene transfer agents. In conjugation (yellow text), donor cells form conjugative pili, typically encoded on plasmids or integrative conjugative elements, through which DNA is transferred. Finally, transformation (red text) is the process by which DNA in the environment is actively taken up by the donor cell. In addition, recent studies have shown that bacteria can also transfer DNA fragments in membrane-bound vesicles and via nanotubes.