Host Specialization of the Prokaryotic Predator Bdellovibrio Bacteriovorus

Abstract

Bdellovibrio bacteriovorus is a small gram-negative bacterium with the ability to parasitize other gram-negative bacteria via periplasmic invasion leading to host cell death. B. bacteriovorus is considered a generalist and as such has been touted as a potential “living antibiotic”. To be useful in treating human/veterinary infections, antibiotics should have minimal impact on commensal microflora, yet the ability of B. bacteriovorus to specialize on specific hosts while ignoring others has not been documented. In this experiment, we investigated the ability of B. bacteriovorus to specialize on one of two different hosts: Escherichia coli or Erwinia amylovora. Our results show that over approximately 875 generations of growth, some B. bacteriovorus populations grown only in the presence of E. coli demonstrate improved growth on E. coli and significantly diminished ability to infect and kill E. amylovora. B. bacteriovorus populations exposed only to E. amylovora show growth deficits on E. coli, but the magnitude of this effect is much smaller and perhaps reflects a longer association of the B. bacteriovorus strain used here with Erwinia spp. in nature. Future work examining the genetic basis of host preference in these populations will allow greater insight into mechanisms of host specialization and serve to inform the utility of B. bacteriovorus as a targeted rather than non-specific "living antibiotic".