Genetic interactions between mixed microbial populations.

Of the various mechanisms by which DNA has been shown to be transferred between bacteria in the laboratory, the combination of promiscuous plasmids and transposable DNA seems the most likely means by which this occurs in Nature. Not only can this lead to the direct transmission of the associated genes, but it can also lead to various structural and genetic changes in other DNA, particularly chromosomal, which might play an important role in microbial evolution. The changes in the DNA in a Pseudomonas strain that has evolved to degrade a novel substrate are considered in this context.