By Mubasher Ahmed, Genetics ‘15

Viral evolution is an emerging field in biology that has great implications for human health. T7 is a phage virus, meaning it infects bacteria, and is a powerful model system in evolutionary virology. In a recent experiment, a team of biologists sought to understand the degree to which genetic elements engineered into the T7 phage genome affected the phage’s rate of propagation. In this context, the genetic elements are sequences of DNA that are inserted between genes that allow for researchers to manipulate gene regulatory networks. This allows biologists to probe how phenotypes change when gene-gene interactions are perturbed.  Previous studies had shown that such genomic elements led to decreased fitness for the virus, but these investigators hoped to better understand how exactly such a system would evolve in laboratory conditions.

To address their questions, the scientists grew both T7 viruses with and without design elements in each of two conditions. One condition was in a nutritious broth that used one intestinal bacterium as a host, and the other in a glucose sugar medium that had a different host bacterium. Both T7 strains were allowed to grow for 700-1000 generations in the glucose media and 100 generations in the broth media. Limitless bacteria were provided for the phages in order to encourage growth, and the researchers hypothesized that their experiment would allow enough time for the maladapted viruses to slough off deleterious design elements through evolutionary adaptation. (more…)