How does chlorine bleach kill bugs?

November 14th, 2008 - 2:55 pm ICT by IANS  

London, Nov 14 (IANS) Chlorine bleach is among the most widely used household disinfectants, yet scientists don’t know exactly how it kills bacteria. A team led by molecular biologist Ursula Jakob of Michigan University described a mechanism by which hypochlorite, the active ingredient of household bleach, attacks bacterial proteins, killing the bugs.

“We did not (exactly) set out to address this question,” said Jakob, an associate professor. “But when we stumbled on the answer midway through a different project, we were all very excited.”

Jakob and her team were studying a bacterial protein known as heat shock protein 33 (Hsp33), which is classified as a molecular chaperone, said a Michigan release.

A chaperone’s job is to protect proteins from unfavourable interactions, a function that’s particularly important when cells are under stress, like high temperatures that result from fever.

“At high temperatures, proteins begin to lose their three-dimensional molecular structure and start to clump together and form large, insoluble aggregates, just like when you boil an egg,” said co-author Jeannette Winter, a postdoctoral fellow in Jakob’s lab.

And like eggs, which once boiled never turn liquid again, aggregated proteins usually remain insoluble, and the stressed cells eventually die.

Jakob and her research team figured out that bleach and high temperatures have very similar effects on proteins. Just like heat, the hypochlorite in bleach causes proteins to lose their structure and form large aggregates.

“Many of the proteins that hypochlorite attacks are essential for bacterial growth, so inactivating those proteins likely kills the bacteria,” said second author Marianne Ilbert, a postdoctoral fellow in Jakob’s lab.

The study was published in Friday’s issue of the journal Cell.

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