Single gene prompts microbes to play versatile roles


Washington : All plant and animal life depends on peaceful coexistence with microbes that help convert food to energy and protect from disease thanks to the role of a single gene.

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With the help of a squid that uses a luminescent bacterium to create a predator-fooling light organ and a fish that uses a different strain of the same species of bacteria to illuminate dark nooks of the reefs, scientists have found that gaining a single gene is enough for the microbe to switch host animals.

The finding by the University of Wisconsin-Madison team is important not only because it peels back some of the mystery of how these bacteria colonise different animals, but also because it reveals a genetic pressure point that can thwart germs making us sick.

“It seems that every animal we know about has microbes associated with it,” says Mark J. Mandel, co-author of the study and a postdoctoral fellow in the UW-Madison School of Medicine and Public Health.

“We pick up our microbial partners from the environment and they provide us with a raft of services from helping digestion to protection from disease,” adds Mandel.

In the Pacific, a species of bacteria known as Vibrio fischeri lives in luminescent harmony with two distinct hosts – the diminutive nocturnal bobtail squid and the reef-dwelling pinecone fish.

In the squid, which feeds at night near the ocean surface, one strain of the bacterium forms a light organ that mimics moonlight and acts like a cloaking device to shield the squid from hungry predators below, said a Wisconsin release.

In the pinecone fish, another strain of the bacterium colonises a light organ within the animal’s jaw and helps illuminate the dark reefs in which it forages at night. The fish light organ may also play a role in attracting the zooplankton that make up the pinecone fish’s menu.

These findings were published in the February issue of Nature.