Magazine article Science News

Bacteria Offer Lessons to Drug Makers

Magazine article Science News

Bacteria Offer Lessons to Drug Makers

Article excerpt

Many bacteria produce poisons that slay microbial competitors while leaving their friends and family--and people--unharmed. In probing one such toxin, scientists believe they've uncovered clues that could lead to better antibiotic drugs.

The toxin they focused on, nisin, belongs to a group of small proteins known as bacteriocins. Food scientists routinely make cheeses and yogurts using starter cultures containing bacteria that produce nisin. As the microbes grow, nisin protects these products from germs causing spoilage or food poisoning, including those responsible for botulism and listeriosis (SN: 2/7/98, p. 89).

Though nisin's germicidal prowess was discovered 71 years ago, the means by which the protein kills bacteria has remained a mystery. In the Dec. 17 SCIENCE, Dutch and German researchers reveal new clues to nisin's potency.

In a series of experiments, Eefjan Breukink of Utrecht University in the Netherlands and his colleagues have demonstrated that the bacteriocin targets an oily substance known as lipid II. Produced inside bacteria, lipid II ferries a pair of sugars through the bacterial membrane to sites where they become building blocks for the microbes' outer cell wall.

By attacking lipid II, Breukink explains, nisin unleashes a double whammy. It not only disables the lipid, an action that alone can kill bacteria, but also creates pores in the cell membrane through which vital ions hemorrhage. This combination of independent effects on lipid II explains nisin's power, Breukink says. In his team's tests, nisin was 1,000 times as toxic to target bacteria as was magainin, a natural antibiotic produced in animals (SN: 3/18/95, p. …

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