Gonorrhea passes from person to person thanks to some clever hitchhiking. For 40 years, researchers thought that Neisseria gonorrhoeae, the bacterium that causes the sexually transmitted disease, glommed on to wiggling sperm during intercourse. But the idea didn’t explain how females passed the STD to males. Now, a new study reported this month in mBio shows that rather than using sperm as a surfboard, N. gonorrhoeae bacteria shoot cables—called pili—onto proteins in the semen to tow themselves through coital liquid. The pili are normally wrapped in bundles (left panel, red arrow), but when exposed to seminal fluid, they unwind into individual strands (right panel, red arrows). This exposes more grappling hooks for transport, boosting the bacteria’s ability to invade by as much as 24-fold. The seminal proteins also help the bacteria attach to skin cells, grown in a dish, that line both the male and female genital tracts, which assists infection. Drugs that unhook gonorrhea’s pili may yield new antibacterials that stymie the transmission of this STD, which infects 100 million people per year.

See more ScienceShots.