Amoeba-Bacteria Symbiosis: Predation, Partnership, and Pathogenesis

Welcome!

Our lab explores the symbiotic spectrum using amoeba-bacteria interactions as a model system. Broadly defined, symbiosis is a "close living together of unlike organsims" (DeBary). As such, symbioses encompass a broad array of interactions that span a continuum of outcomes; from parasitism to mutualism. Our lab uses the social soil-dwelling amoeba Dictyostelium discoideum as a focal eukaryotic host for bacterial symbionts. First, we identify and characterize natural bacterial symbionts of soil amoebas. Next, we explore the outcomes, contextual modifiers, evolutionary pressures, and mechanisms underlying these symbiotic interactions. Ultimately, we hope that this micro-biological system can be applied to address macro questions about organismal interactions; such as:

How are interactions influenced by ecological context?

What factors promote symbiont fidelity vs. promiscuity and how are species barriers maintained or overcome?

What forces shift the evolutionary trajectory of interactions?

And- What are the molecular mechanisms that underlie antogonistic vs. mutualistic interactions and how do these factors mediate outcomes?

Dictyostelium discoideum

D. discoideum normally lives in soil and loose leaf litter. It has a unique life-cycle, transitioning from single cellular to multicellular stages. When in the amoeba vegitative stage, cells eat bacteria via phagocytosis and multiply through binary fission. When amoeba numbers are high and food is depleted, amoebas can either transition to a social or a sexual stage. In the social stage, amoebas aggregate to ultimately form a multicellular fruiting body, consisting of a thin stalk of dead structural cells supporting a bulb like sorus containing hardy reproductive spore cells. When spores are dispersed to new favorable environments, they germinate into vegitative amoebas and the cycle continues.

Methodology

We use a variety of methods, including general microbiological and molecular techniques, fluorescence microscopy, and flow cytometry.