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Sunday, November 28, 2010

Bacteria fight with toxic darts

Researchers at the University of California—Santa Barbara have found that some bacteria conduct advanced warfare on their competition. They inject toxic darts into their opponents.

The bacteria in question, which include some common pathogens, have cell surface proteins that contain toxic dart tips. The toxic dart is delivered into the victim cell in a process called ‘contact dependent growth inhibition’. In other words, the two cells must be touching to trigger this response. The attacked cell is sometimes killed, but often is simply prevented from further growth and reproduction (similar to many of our synthetic antibiotics). For example, the toxin might enter the enemy cell and chop up RNA, preventing protein synthesis. In any case, the attacked cell is removed from competition for resources.

As with all types of biological warfare, there are countermeasures. Some bacteria have an immunity protein on their cell surface that acts as a shield against the toxin. This ‘contact dependent growth inhibition immunity’ inactivates the toxic dart.

Up to 50 distinct toxic-tip proteins have been discovered, each with its own antidote (at a minimum, each bacteria carries the shield against its own toxin). The biologists hope that this discovery will yield an advantage in the war against pathogens, especially in this era of increasing antibiotic resistance.