Study shows unified process of evolution in bacteria and sexual eukaryotes and opens door to concept of ‘species’ in bacteria

By Denise Brehm
Civil & Environmental Engineering

Bacteria are the most populous organisms on the planet. They thrive in almost every known environment, adapting to different habitats by means of genetic variations that provide the capabilities essential for survival. These genetic innovations arise from what scientists believe is a random mutation and exchange of genes and other bits of DNA among bacteria that sometimes confers an advantage, and which then becomes an intrinsic part of the genome.

But how an advantageous mutation spreads from a single bacterium to all the other bacteria in a population is an open scientific question. Does the gene containing an advantageous mutation pass from bacterium to bacterium, sweeping through an entire population on its own? Or does a single individual obtain the gene, then replicate its entire genome many times to form a new and better-adapted population of identical clones? Conflicting evidence supports both scenarios.

In a paper appearing in the April 6 issue of Science, researchers in MIT’s Department of Civil and Environm