Bacteria live in a state of perpetual warfare, with different species battling for dominion over their competitors and when pathogen, over their infected host. New research suggests that the human pathogen Vibrio cholerae, which causes the disease cholera, kills off its microbial rivals by jabbing them with a spring-loaded poison dagger. Were it not for that defense, called the Type 6 secretion system (T6SS), V. cholerae might not out-compete its neighbors to sicken millions of people every year.

The results were published online February 26 in Nature.

The research began with a hypothesis that cholera’s T6SS tactic mirrors the system that phage viruses—viruses that infect bacteria—use to inject their genetic material into bacteria for replication. But this hypothesis was grounded in biochemical evidence, in that the phage and T6SS components appeared to have similar protein structures. The only way to confirm the hypothesis was to watch the T6SS system in action. So John Mekalanos, chair of the Department of Microbiology and Immunobiology at Harvard Medical School, and Grant Jensen, an associate professor of biology at the California Institute of Technology, teamed up to image the T6SS system working in real-time.