Mutation may slow disease progression

UH evolutionary biologist Tim Cooper and his team have found a genetic mutation that may slow the progression of chronic disease.

Cooper and his team have spent the past five years studying a bacterial population that came from an experiment that begun in 1988 by Dr. Richard Lenski.

“We use a simple test to determine whether one bacterium is more fit than another,” Cooper said. “We simply count the number of cell divisions different bacterial types go through as they compete together. The more cell divisions a bacterium has the more offspring it leaves and the higher its frequency becomes in a population. We know that the mutations we see cause fitness to increase, but we don’t know exactly how.”

The fitness of the bacteria population coincides with fitness of an actual person.

“Fit refers to the effect a mutation has on the ability of a mutated individual to compete with other individuals and to have more offspring,” Cooper said. “The mutations we studied are called beneficial because they act to change individuals in a way that makes them more fit.”

Once the interactions between the mutations can be understood, the results become applicable to both natural bacterial populations and bacterial populations that evolve in humans, said a news release.

“What we see at the level of the effect of the mutations on the fitness of the bacteria is that they tend to interfere with each other,” Cooper said. “When we combine two mutations in one bacterium and measure their effect on fitness, we tend to get smaller effects than we predicted from knowing the individual effects of the two mutations. Exactly why we see this is not yet known.

“We think our findings are probably general to the process of adaptation in a relatively constant environment,” Cooper said. “Several disease causing microorganisms might find themselves in this situation, perhaps especially bacteria that cause chronic diseases like cystic fibrosis. The bacteria that causes the problems of this disease tend to remain associated with a single patient for decades and so it has plenty of opportunity to evolve to increase their fitness in the patient.”