Environment and Ecology

Honorable Mention: Amanda Ruiz, University of California, Irvine
Bottleneck and Massive Passage Dynamic Promote Drastic Variation on RNA Virus Fitness

The high mutation rate in RNA viruses makes them a perfect system in which to study evolution. Vesicular stomatitis virus (VSV) is an RNA virus that has commonly been used to study evolutionary processes for several decades. In this study, we have analysed the effects of bottleneck and massive passages on the fitness of two mutant strains of this virus. We subjected ten viral lines of one strain to fifteen bottleneck passages followed by five massive passages. At the end of the first evolution, samples showed fitness decreases, apart from three replicates with unaltered fitness, whereas at the end of the second evolution, almost all viral populations recovered fitness, in some cases showing higher fitness than the ancestor strain. Ten viral lines of the other strain were subjected to fifteen massive passages followed by five bottleneck passages. The first evolution promoted fitness increases in all cases, whereas the second evolution showed general fitness decreases, though differences were not significant. Thus, we conclude that massive passages promote an increase in overall fitness, while bottleneck passages promote a decrease in overall fitness, but to a lesser extent. The study of evolutionary processes of RNA viruses will aid in our understanding and perhaps control of many harmful diseases affecting human population.