Fatal attraction: bacterial bait lures worms to their death.

D uring the past decade, the roundworm Caenorhabditis elegans has become a popular model for the study of host/ pathogen relationships, leading to a wealth of information about microbial virulence factors and host defense pathways (1). Although the complicated interactions between C. elegans and the many pathogens that it encounters in the soil have become clearer in recent years, there is still much to learn. What are the cues that worms use to detect food sources? How do worms choose which bacterial species to eat and which to leave alone? Once a pathogen is encountered, what are the microbial killing mechanisms and the nematode’s survival mechanisms? The paper by Niu et al. (2) in PNAS provides a rare 360° view of one C. elegans/pathogen relationship. It describes the Bacillus nematocida signals that attract C. elegans, the virulence factors it uses to kill worms from within, and the specific host proteins targeted.