( The ubiquitous bacteria E. coli rank am...)DNA: Bacteria's survival ration

A research team led by Steven Finkel, assistant professor of molecular and computational biology in the USC College of Letters, Arts and Sciences, had already shown that DNA is an acceptable source of nutrients for bacteria.

The team's latest study, presented in the June 1 issue of the Journal of Bacteriology, finds that DNA is a critical food source in the battle of the fittest. Bacteria that stay alive just a little longer than their counterparts get a double reward: the competition for food lessens, and the supply of nutrients increases.

"The bacteria actually eat the DNA, and not only that, they can use the DNA as their sole source of nutrition," Finkel said.

In hindsight, it should come as no surprise that DNA can serve as a meal for microbes.

"You're surrounded by living things, and living things die," Finkel said. "Where does all that stuff go? Why aren't we up to our ears in DNA, in ribosomes, in plant protein?

"A lot of decay is microbial, and nobody ever thinks about it."

Finkel calls this phenomenon "nutritional competence" to distinguish it from natural competence, defined as the ability of cells to assimilate waste DNA in order to mutate or repair their genomes.

Natural competence is potentially risky, Finkel said, since bad mutations can result, "but there should be no genetic cost to eating [the DNA]."

The study identified eight genes in E. coli that are necessary for nutritional competence. Without any one of these genes, the bacteria cannot consume DNA and lose their competitive advantage.

"The gene family is found in many other species," the authors reported, "suggesting that the use of DNA as a nutrient may be a widespread pheno
'"/>

Source:University of Southern California