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Bdellovibrio bacteriovorusHD100 is an obligate predator that invades and grows within the periplasm of Gram-negative bacteria, including mcl-polyhydroxyalkanoate (PHA) producers such asPseudomonas putida. We investigated the impact of prey PHA content on the predator fitness and the potential advantages for preying on a PHA producer. Using a new procedure to controlP. putidaKT2442 cell size we demonstrated that the number ofBdellovibrioprogeny depends on the prey biomass and not on the viable prey cell number or PHA content. The presence of mcl-PHA hydrolysed products in the culture supernatant after predation onP. putidaKT42Z, a PHA producing strain lacking PhaZ depolymerase, confirmed the ability ofBdellovibrioto degrade the prey's PHA. Predator motility was higher when growing on PHA accumulating prey. External addition of PHA polymer (latex suspension) toBdellovibriopreying on the PHA minus mutantP. putidaKT42C1 restored predator movement, suggesting that PHA is a key prey component to sustain predator swimming speed. High velocities observed inBdellovibriopreying on the PHA producing strain were correlated to high intracellular ATP levels of the predator. These effects broughtBdellovibriofitness benefits as predation on PHA producers was more efficient than predation on non-producing bacteria.