Jack-of-all-trades or master of one? Viruses show tremendous diversity in their ability to infect different types of organisms including animals, plants and bacteria. Some viruses are able to infect multiple host species while others can only infect one. A major unresolved problem facing both the scientific community and medical professionals is why do some viruses evolve to be specialists while others are generalists? To answer this question, it is vital to understand the complexities underpinning the interactions between hosts and their viruses. As viruses and their hosts co-evolve, hosts develop resistance, and viruses in turn find ways of overcoming host defenses. Whether the virus can successfully co-evolve with its host also depends on the structure of the environment and how the viruses are transmitted between hosts. This research will embrace the complexity of virus and host interactions - from genes to cells to populations to the community. A laboratory system consisting of a bacteria (Escherichia coli) and its viruses will be used to gain understanding of the evolution of naturally occurring viruses and their hosts. The experiments will be combined with an innovative mathematical modeling framework designed to bridge the gap between laboratory and nature. The results of this work will provide critical insights into what dictates the diversity of viral strategies - a key step towards a comprehensive theory of the ecology and evolution of infectious diseases. This will further a general understanding of the dynamics of disease in natural systems and help to improve public health initiatives. The project will strengthen collaborations between US and UK scientists and train undergraduate and graduate students in research.

Project Report

Many plants, animals and microbes coevolve with one another, where one species evolves in response to another, and vice versa. The coevolutionary process is often difficult to document because many organisms have generation times that are too long to witness the evolutionary process over the course of an experiment. However, microbes, such as bacteria and viruses, have such fast generation times that coevolution can be witnessed in real-time. Our research project used laboratory communities of bacteria and viruses to understand the processes driving coevolution. We investigated the role of the environment in the coevolutionary process between the bacterium Escherichia coli and the virus Lambda during a 20 day long coevolutionary experiment. Using experiments where we changed the type of resources in the environment (sugars that provide food for the bacteria) and genetic analyses of the results of the experiments, we found different types of genes confer resistance in the bacteria, and the mutations in these genes depended on what type of resource environment the bacteria and virus were in. The results of these experiments were linked to a mathmatical model designed to bridge the gap between laboratory and nature. This study underlines that environment is an important force for coevolutionary dynamics in virus-bacteria systems. It also highlights the complexity of the mechanisms responsible for the evolution and the ecology of coevolving organisms in the wild. Finally, the work has broader implcations for understanding of the dynamics of disease in natural systems and can help to improve public health initiatives, as viruses and their hosts (humans and otherwise) also undergo coevolutionary interactions.

National Science Foundation (NSF)
Division of Environmental Biology (DEB)
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Samuel M. Scheiner
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University of California Santa Cruz
Santa Cruz
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