Researchers Learn How Bleach Kills Bacteria

Article

ANN ARBOR, Mich. -- Developed more than 200 years ago and found in households around the world, chlorine bleach is among the most widely used disinfectants, yet scientists never have understood exactly how the familiar product kills bacteria. New research from the University of Michigan, however, reveals key details in the process by which bleach works its antimicrobial magic.

In a study published in the Nov. 14 issue of the journal Cell, a team led by molecular biologist Ursula Jakob describes a mechanism by which hypochlorite, the active ingredient of household bleach, attacks essential bacterial proteins, ultimately killing the bugs.

"As so often happens in science, we did not set out to address this question," said Jakob, an associate professor of molecular, cellular and developmental biology. "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. The main job of chaperones is to protect proteins from unfavorable interactions, a function that's particularly important when cells are under conditions of stress, such as the 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 lead author Jeannette Winter, who was 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.

These findings are not only important for understanding how bleach keeps our kitchen countertops sanitary, but they may lead to insights into how we fight off bacterial infections. Our own immune cells produce significant amounts of hypochlorite as a first line of defense to kill invading microorganisms. Unfortunately, hypochlorite damages not just bacterial cells, but ours as well. It is the uncontrolled production of hypochlorite acid that is thought to cause tissue damage at sites of chronic inflammation.

How did studying the protein Hsp33 lead to the bleach discovery? The researchers learned that hypochlorite, rather than damaging Hsp33 as it does most proteins, actually revs up the molecular chaperone. When bacteria encounter the disinfectant, Hsp33 jumps into action to protect bacterial proteins against bleach-induced aggregation.

"With Hsp33, bacteria have evolved a very clever system that directly senses the insult, responds to it and increases the bacteria's resistance to bleach," Jakob said.

Source: University of Michigan

 

 

 

Related Videos
Infection Control Today Topic of the Month: Mental Health
Infection Control Today Topic of the Month: Mental Health
Infection Control Today Topic of the Month: Mental Health
Cleaning and sanitizing surfaces in hospitals  (Adobe Stock 339297096 by Melinda Nagy)
An eye instrument holding an intraocular lens for cataract surgery. How to clean and sterilize it appropriately?   (Adobe Stock 417326809By Mohammed)
Set of white bottles with cleaning liquids on the white background. (Adobe Stock 6338071172112 by zolnierek)
Association for the Health Care Environment (Logo used with permission)
Woman lying in hospital bed (Adobe Stock, unknown)
Photo of a model operating room. (Photo courtesy of Indigo-Clean and Kenall Manufacturing)
Mona Shah, MPH, CIC, FAPIC, Construction infection preventionist  (Photo courtesy of Mona Shah)
Related Content