<i>V. parahaemolyticus</i> exhibit intra-species virulence.

<p>(<b>A–B</b>) Viability counts before (0 h) and after (4 h) co-culture of prey environmental <i>V. parahaemolyticus</i> isolates containing a pBAD33 vector (<b>A</b>), with attacker <i>V. parahaemolyticus</i> POR1 or POR1Δ<i>hcp1</i> strains containing an empty pBAD vector (<b>B</b>). (<b>C–D</b>) Viability counts before (0 h) and after (4 h) co-culture of prey POR1Δ<i>hcp1</i> strains containing an empty pBAD vector (C) with attacker T6SS1-positive environmental <i>V. parahaemolyticus</i> isolates containing a pBAD33 vector (<b>D</b>). Mixed cultures at an OD₆₀₀ ratio of 1∶4 (prey:attacker) were spotted on MLB plates at 30°C.