An efficient method for visualizing the plaques of Bdellovibrio bacteriovorus

Bdellovibrio bacteriovorus, an obligate predator of Gram-negative bacteria, has emerged as a promising natural antibiotic to combat the escalating threat of antibiotic resistance. Plaque forming units (PFU) counting is commonly used to determine the viable numbers of B. bacteriovorus. However, nearly three-days incubation is always necessary for getting the single, obvious plaques on the double-layer agar plate. This time-consuming procedure greatly impedes the purification and enumeration efficiency of B. bacteriovorus. Until now, no simplified method has been developed to address this issue. In this work, we evaluated the advantages of using fluorescent prey to enhance the visualization of the B. bacteriovorus plaques. Our work reveals that the regular single plaques are easily observed under the enhanced background of fluorescent prey lawn in one and a half days, reducing nearly half of the time consumption in the purification and enumeration of B. bacteriovorus.