Evolutionary strategies of Bdellovibrio bacteriovorus predators and prey

Antibiotic resistance is a serious threat to human health and new treatments for bacterial infections are urgently needed. Bacteriophages, first used at the beginning of the 20th century, and the predatory bacterium Bdellovibrio bacteriovorus (discovered in 1962) are potential alternatives to antibiotics. We developed a mathematical predator prey model to explore the effects of Bdellovibrio and bacteriophage on prey bacterial numbers. Our system has an abiotic resource that is consumed by the E. coli prey following Monod kinetics and up to two predator species with Holling type I or type II functional responses. As Bdellovibrio spends considerable time in the periplasm of its prey as a ‘bdelloplast’, this stage is also modelled, giving a delay between prey removal and ‘birth’ of predators. We used the model to examine the effects of Bdellovibrio and a bacteriophage on prey populations and found a distinct difference in effectiveness between Bdellovibrio and bacteriophages. We also looked at how various biological factors change predation effeciency. We found that there is an optimal predator:prey ratio for the predator. We also discovered that there is an optimal attack rate and an optimal mortality for the predator.