An efficient method for visualizing the plaques ofBdellovibrio bacteriovorus

Abstract

Bdellovibrio bacteriovoruspreys upon other Gram-negative bacteria. This obligate predator is recognized as a living antibiotic to control the rising problem of antibiotic resistance. Plaque forming units (PFU) counting is commonly used to determine the viable numbers ofB. bacteriovorus. However, nearly 3-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 ofB. bacteriovorus. In this work, we evaluated the advantages of fluorescent prey on the plaque visualization of the predator. Our study reveals that plaques of theB. bacteriovorushave already formed before they could be monitored by eyes on the double layer agar plate. The regular single plaques are easily observed under the enhanced background of fluorescent prey lawn in 1.5 days, reducing nearly half of the time consumption in the purification and enumeration ofB. bacteriovorus. In addition, it also provides some paradigms for modeling and testing the subtle predation process on the solid medium.IMPORTANCEThe viability of predatorBdellovibrio bacteriovorusis typically suggested by the lysis of the prey bacteria on the double layer agar plate. However, long period incubation is necessary to get single obvious plaques ofB. bacteriovorus. Here, we found that plaques are already generated before it can be monitored by eyes. The plaques are obvious on the enhanced background of the double layer agar plate in the presence of fluorescent prey under UV light. We confirmed that the utilization of fluorescence labeled prey bacteria reduces the time spent on the isolation, purification, and enumeration of the predatorB. bacteriovoruson the double layer agar plate.