Gut Bacteria Help Roaches Get Together

When cockroaches want to huddle up, the insects sniff out aggregation pheromones in each other’s poop. A study now shows that the production of these volatile compounds depends on the specific microbes in a roach’s gut (Proc. Natl. Acad. Sci. USA 2015, DOI: 10.1073/pnas.1504031112). A team led by Coby Schal of North Carolina State University analyzed German cockroach waste and found 40 volatile carboxylic acids acting as aggregation pheromones. But feces from axenic cockroaches—those raised under sterile conditions with no microorganisms in their gut—lacked many of these pheromones. In side-by-side tests, cockroach nymphs were more attracted to the feces of control roaches than that of axenic roaches. But after the team inoculated axenic roaches with six bacteria species cultured from control roaches, feces from the microbially colonized roaches also attracted nymphs. The team further created a synthetic blend of six pheromones based on compounds found in the control group’s feces. That mix was better at attracting nymphs raised in the same environment as the control cockroaches than a commercial pheromone blend that came from unrelated roaches.