In search of prey: polyamine usage by Bdellovibrio as a chemosensory ligand and regulator of bacterial predation

Growth of the bacterial predator Bdellovibrio bacteriovorus is dependent upon locating and consuming susceptible Gram-negative prey bacteria. Its bi-phasic lifecycle includes an extracellular free-swimming phase, during which efficient location of prey cells is essential to survival, and an intra-periplasmic growth phase, during which Bdellovibrio uses the prey cell contents to grow and replicate. Polyamines are cations made by all forms of life, including humans, plants, and many bacterial species. In bacteria they have been shown to be involved in regulating cell growth, biofilm formation and virulence. Our lab is interested in the signals that are involved in both of the phases of the Bdellovibrio life cycle. Together with our collaborators, we have shown that polyamines can act as a chemosensory ligand, and may allow Bdellovibrio to swim towards areas of high bacterial cell density. We have also shown that the synthesis by Bdellovibrio of one polyamine is required for timely completion of the predatory cycle.
The chemosensory system of Bdellovibrio is complex and we are only just beginning to understand the range of signals that are sensed, whilst the regulatory networks underlying predation are equally complex. Our studies are beginning to elucidate each of these two systems in Bdellovibrio and are paving the way for further understanding of this complex, intriguing, bacterial predator.