MargaretMcFall-Ngai researches how benign bacteria affect us at the genetic level. TheUniversity of Wisconsin developmental biologist says that there are uniquecommunities of health-promoting bacteria in many tissues including the skin,nasal passages, eyeballs, and our digestive systems.
Killingthese bacteria can even leave us prone to diseases. McFall-Nigh notes, forexample, that a woman's vagina normally hosts hundreds of types of bacteria.After a treatment of antibiotics, she says, yeast infections are more likely.So there are all these different areas of the human body that require, fortheir health, interactions with communities of co-evolved microbes.
McFall-Ngaipoints out that most of our bacterial associates cannot be grown in a lab.Furthermore, determining how any single species of bacteria affects us isdifficult. So McFall-Ngai studies a simpler system: an animal which has aspecial relationship with just one type of bacteria? the Hawaiian bobtail squidand the bacteria .
Thetiny bobtail squid has a head about three centimeters long and feeds on shrimpin shallow coastal waters. Its bacterial partner, , livesinside the squid and receives nutrients. In exchange for the food, the bacteriaproduce light. The squid usually hunts at night and without any camouflage itwould cast a shadow.Instead, the squiduses the bacteria to emit light of the same intensity and color as down-glowingmoonlight and starlight and avoids detection from below.
Boththe squid and the bacteria can be grown in the lab independently. When theypartner up, the bacteria cause the squid cells to change which of their genesare active. Many of these altered genes are also present in mice and humans.Some of them act in the immune response against pathogens.
McFall-Ngaicompares these bacteria-induced genetic changes to a language and says itdoesn't seem to matter whether the bacteria inducing those changes aredisease-causing or health-promoting. Although the same language appears to beused, it's the difference between an argument and a civil conversation.
Understandingthe language our bodies use to communicate with bacteria is important toimproving medical treatment. Current antibiotics often kill both the bad andthe good bacteria, leaving room for opportunistic pathogens to colonize. So, ifwe want better treatments against our foes, we need to learn how we talk to ourfriends.