Bacterial predator-prey interaction at low prey density.

A bacterial predator-prey interaction was studied using Bdellovibrio and bioluminescent prey bacteria. The attacking bdellovibrio causes decay of bioluminescence, which is correlated with bdellovibrio penetration into the prey. The behavior of the prey and predator populations over time was found to be well described by a Lotka-Volterra model. By using this model, the probability of bdellovibrio penetration after encountering a prey cell was found to be approximately 3.0%. The prey density required to give the bdellovibrios a 50% chance of survival was calculated to be at least 3.0 x 10 cells per ml, and the density required for population equilibria was calculated to be about 7 x 10 prey bacteria per ml. These values, not generally characteristic of natural habitats, suggest that the existence of Bdellovibrio in nature is limited to special ecological niches.