Florida Museum of Natural History graduate student Julie Allen recently received the 2009 Best Paper Award from the University of Florida biology department.

Allen won the award for her paper on mutualistic bacteria, which live in some insects. The article appeared in the academic journal PLoS ONE in March 2009. PLoS ONE is an interactive open-access journal for the communication of all peer-reviewed scientific and medical research.

Allen is studying organisms that have been evolving together over time like hosts, parasites and mutualists. Her paper, “Mutational Meltdown in Primary Endosymbionts: Selection Limits Muller’s Ratchet,” is the second chapter of her dissertation.

“There is a well-known phenomenon in certain bacteria where mutations in the DNA start to pile up and aren’t being fixed,” said David Reed, Florida Museum associate curator of mammals and Allen’s advisor. “This runaway mutation usually has dire consequences. Julie’s research shows that in some types of bacteria, the runaway mutation starts to slow down over time, which might explain why some bacteria can persist despite having many deleterious mutations.”

Allen said these bacteria provide nutrients to insects, allowing them to live on food sources they normally would not. They do this, presumably, in return for housing within the insect. Although the insect is a good place to live, there are evolutionary consequences to the bacteria because they have very small population sizes. Small population sizes accumulate harmful mutations over time and ultimately may go extinct.

“The paper suggests that after a few million years, natural selection decreases the mutation accumulation in the bacterial populations,” Allen said. “This may explain why these bacteria have survived over tens of millions and even hundreds of millions of years.”

Read the article online on PLoS ONE.

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