V. cholerae Is Highly Virulent Toward E. coli in a T6SS-Dependent
Manner. Because V52 exhibited the highest killing efficiency toward
E. coli, we selected E. coli K-12 as experimental prey for
future experiments. Rifampicin-resistant E. coli MG1655 prey
was mixed with a rifampicin-sensitive predator, either self or
V. cholerae strain V52, in a killing assay described in Materials
and Methods. When E. coli was mixed with rifampicin-sensitive
self, E. coli survival was on the order of 108 colony-forming units
(cfu)·mL−1 (Fig. 2A). Remarkably, in the presence of the V52
predator, up to a 100,000-fold reduction in culturable E. coli was
observed (Fig. 2A). The dramatic virulence exhibited by V52 was