Predation of E.coli High-Persister Strain (MGHY) By Bdellovibrio bacteriovorus 109J

Bdellovibrio bacteriovorus 109J is a gram-negative bacterium that preys upon other gram-negative bacteria, including human pathogens. The potential of predatory bacteria as “living antibiotics” is evaluated. A troubling fact of antibiotic resistance is the phenomenon of persister cells. This work addressed the issue of predation upon persister strains.

Persister suspensions of the high-frequency E. coli persister strain, was obtained by incubating freshly grown cultures to 100 mg.ml^-1 ampicillin for 6h,s with a yield of 0.1%. After washing, the concentrated suspensions was exposed to attack phase Bd. The persister strain was preyed upon, resulting in a decrease of five orders of magnitude. No significant difference was obtained with control cultures of MGHY incubated for 6 h without antibiotics prior to exposure to the predator.

Predation by Bd upon a prey suspension does not lead to prey eradication, with a resulting low level of prey population that is phenotypically resistant to predation. In order to examine whether such predation-resistant cells exhibit increased or decreased persistence, MGHY was exposed to Bd for 36h. The remaining cells were exposed to ampicillin for 18h, resulting in a decline by three orders of magnitude. Control samples of cells exposed to the antibiotic and incubated for 36h in the absence of the predators did not differ significantly.

In conclusion, persister cells appear to be sensitive to Bd predation, and predation-resistant cells are not impaired in their ability to persist in the presence of antibiotics. This suggest that the two phenomena are not linked.