Parasitic Sex Puppeteers; April 2002; Scientific American Magazine; by Laurence D. Hurst and James P. Randerson; 6 Page(s)

Don't bite the hand that feeds you. The old adage sums up the approach parasites are expected to take with their victims. A freeloader that can spread only when its host reproduces ought not to be overly harmful: too much damage to its unwilling benefactor will affect the parasite's own chances to procreate. This scheme contrasts with the tactics of a pathogen that has a short infectious period, such as the flu virus. In that case, the virus has no long-term interest in the carrier's well-being, so a "get transmitted quick" strategy is favored almost regardless of the cost to the hapless host.

The widely distributed bacterium Wolbachia (a close relative of the gut bacterium Escherichia coli) is a boarder with a long-term interest in its invertebrate host. It lives within cells and is transmitted to the next generation by invading its host's eggs. Contrary to the old saying, however, the bacterium engages in various radical manipulations of its hosts, including killing male offspring, turning males into females and rendering some host matings infertile. If Wolbachia's reproduction is so intimately tied up with that of its meal ticket, why does it create so much havoc?