November 13, 2008

Researchers Discover How Bleach Kills Germs

US scientists said after more than 200 years they have finally discovered how bleach kills germs.

Researchers at the University of Michigan said it seems that hypochlorous acid, the active ingredient in bleach, attacks proteins in bacteria, causing them to clump up much like an egg that has been boiled.

However, they say the discovery came about by accident.

"As so often happens in science, we did not set out to address this question," said Ursula Jakob, who led the team.

The team was researching a bacterial protein called heat shock protein 33, which is a kind of molecular chaperon that becomes active when cells are in distress, for example from the high temperature of a fever.

The discovered the source of the distress was hypochlorous acid or hypochlorite. But Jakob's team figured out that bleach and high temperatures have very similar effects on proteins.

Once the bacteria were exposed to bleach, the heat shock protein became active in an attempt to protect other proteins in the bacteria from losing their chemical structure, forming clumps that would eventually die off.

Marianne Ilbert, a postdoctoral fellow in Jakob's lab, said many of the proteins that hypochlorite attacks are essential for bacterial growth, so inactivating those proteins likely kills the bacteria.

The human immune system produces hypochlorous acid in response to infection but the substance does not kill only the bacterial invaders, the researchers said.

It also kills human cells, which may explain how tissue is destroyed in chronic inflammation.

Jakob, whose study was published in the journal Cell on Thursday, said hypochlorous acid is an important part of host defense.

"It's not just something we use on our countertops."


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