Evolution Experiments with Bacteria
This article in Science is about experiments using 30,000 or so generations of bacteria to look at evolution. One lab found only one beneficial mutation in that time, but they found that 12 different populations all evolved to get the same fitness ina new environment, but using different methods and with different DNA. Here’s one excerpt to give the flavor:
Originally, Adams explains, natural selection favored mutants that had a souped-up appetite for glucose and so could outgrow its neighbors. But bacteria can metabolize only so much glucose; as their biochemistry got clogged with the sugar, the glucose-hogging mutants shunted the excess from aerobic metabolism to the less efficient anaerobic pathway, which generates a waste product, acetate. As Rosenzweig, Adams, and their colleagues described in the August 1994 issue of Genetics, the acetate buildup created a new ecological opportunity, and eventually a mutant emerged that could fill it: a new acetate-scavenging strain. Adams and his colleagues reported last summer in Molecular Biology and Evolution that the acetate scavengers appeared in six out of 12 populations they studied, and each time a mutation in the regulatory region of a gene that influences acetate uptake was responsible.
“It’s the first stage in speciation,” says Adams. “Diversity can exist even if you don’t seed it with something that can drive diversification.” And like other studies, this one shows that diversification is not only inevitable but also follows a predictable course.