Electronic Theses and Dissertations

Date of Award


Document Type


Degree Name

M.S. in Biological Science



First Advisor

Peter C. Zee

Second Advisor

Jason Hoeksema

Third Advisor

Susan Balenger

Relational Format



The selection pressure of predation has encouraged the development of defense traits that can make an individual species more environmentally stable. In addition to biotic pressures, abiotic factors could lead to disruption of predator-prey balance within ecosystems. Consequently, it is significant to better understand how environmental factors can influence predator-prey interactions and how responses may, in turn, affect communities. A current challenge within microbial communities is to understand which intraspecific traits associated with such defense strategies are important for microbial-prey responses to predation, and how the responses vary across environments revealing GxE interactions. In this study, I examined microbial-predator prey interactions using social bacterium Myxococcus xanthus as prey to Caenorhabditis elegans and Pristionchus pacificus nematode predators within laboratory-controlled microenvironments. I combined quantitative analyses with growth rate calculations to an experimental approach to measure the effects of temperature, resource availability, and predator presence on the defense response of various M. xanthus genotypes. I found that traits associated with full motility were effective responses to nematode predation, and that deficient defense strategies of M. xanthus were consequences of life-history trade-offs and lack of Type IV pili. In addition, I discovered that M. xanthus possess generalist defense traits, as opposed to specific, and expressed such traits relatively equally in response to two distinct nematode predators. Finally, I found that the effectiveness of defense traits by M. xanthus varied across an abiotic gradient when exposed to predation, and that temperature was the leading determinate in the outcome (i.e., effectiveness of defense) of the species-interaction.



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