D3271: Exploring the growth dynamics and infectivity of cultured Crithidia bombi on host bumblebees Bombus impatiens

Crithidia bombi is a common flagellated parasite of bumblebees that is orally transmitted through feces and affects bumblebee foraging behavior and colony health. Culturing C. bombi provides opportunities for lab experiments. Still, the rate at which C. bombi grows, its favorable conditions, and its effectiveness at infecting bees from cultured media are little researched. 

 My research evaluates optimal conditions for growing C. bombi by performing sterile cell culturing techniques. By assessing the ability of different life stages to infect bumblebees, we hope to pinpoint the specific growth stage at which C. bombi is most infectious under different biological assay conditions. 

To understand growth dynamics and infectivity of C. bombi under different conditions, two sets of experiments will be performed. The first experiment will determine the time frame for lag, exponential, and stationary phases of cells cultured in growth media incubated at 27 °C for 7 days. After the timing of each is identified, experiment 2 will inoculate healthy bees with cells from each phase, followed by dissection to quantify infectivity of those stages on host bumblebees (Bombus impatiens). We hypothesize that C. bombi grows in a sigmoidal curve (using lag, exponential, stationary stages) and expect the exponential reproductive stage to be the most infective, because the cells will be in an active stage of reproduction. Comprehending how culture conditions and cell growth stages affect infectivity allows for effective experimental protocols and greater consistency of research outcomes.