researchPublished 2006
Genome sequencing sheds light on microevolutionary processes
Greg Velicer of the Max Planck Institute for Developmental Biology in Germany, Stephan Schuster and collaborators have used whole-genome sequencing to demonstrate that just a handful of mutations can lead to major differences between bacterial clones.
Their study organism, Myxococcus xanthus, is a soil proteobacterium with one of the largest known bacterial genomes (9.14Mb). The ancestral clone of M. xanthus is cooperative: under nutritional stress, each bacterium cooperates with conspecifics to generate spore-producing fruiting bodies (left). A "cheating" clone lacking this behavior was derived by culturing the original clone in nutrient-rich medium for 1000 generations. A third clone was generated by subjecting mixed cultures of the first two clones to alternating cycles of starvation and resource excess. This third clone regained the cooperative characteristics of the first.
Using a combination of sequencing methods, the researchers identified 14 mutational changes between genomes of the the first and second clone, but just one change between the behaviorally-distinct second and third clones. All mutations were single base pair differences.
In a May 2006 issue of PNAS, the researchers discuss how their findings help elucidate the evolutionary processes that drove these mutations to fixation or detectable frequency.
» Read the abstract on the PNAS website