Ecology and Population Structure of Vibrionaceae in the Coastal Ocean

Sarah Pacocha Preheim, Ph.D., 2010
Martin Polz, Advisor

Extensive genetic diversity has been discovered in the microbial world, yet mechanisms that shape and maintain this diversity remain poorly understood. This thesis investigates to what extent populations of Vibrionaceae are ecologically specialized by investigating the distribution across a wide range of environmental categories, such as marine invertebrates or particles in the water column. Additionally, it seeks to determine whether in situpopulation distributions directly result from a competitive advantage over other Vibrio populations using in vitrocompetition assays on mixtures of native, sterilized particles. Generalist populations were found to dominate the associations with marine invertebrates, consistent with a model of high migration dominated population assembly. A majority of populations occurred broadly within and among the different types of invertebrates sampled, with one population being a near perfect generalist. Specialization, demonstrated by specific and reproducible association with different particle types in the water column, is more common than specialization within invertebrate hosts. Relative growth advantages of specialist populations in competition with other Vibriopopulations on native particles may not be sufficient to explain observed environmental distributions. This highlights the importance of comparing multiple environmental categories and migration among them to investigate population structure and adaptation.