How household bleach works to kill bacteria

November 13, 2008,

Despite the fact that household bleach is commonly used as a disinfectant, exactly how it works to fight bacteria remained an open question. Now, a report in the November 14th issue of the journal Cell, a Cell Press publication, provides an answer.

The researchers found that hypochlorous acid, the active ingredient in bleach, causes the unfolding of proteins in bacteria in much the same was that heat stress or fever does. Those denatured proteins then clump together irreversibly into a mass in living cells, similar to what happens to proteins when you boil an egg, according to the researchers.

The bacteria aren't totally defenseless, however. Under those circumstances, a protein chaperone called heat shock protein Hsp33 springs to action, protecting proteins from the aggregation effect and increasing the bacteria's bleach resistance. Protein chaperones are generally defined as proteins whose function is to help other proteins.

" We found both in vitro and in vivo that bleach attacks proteins," said Ursula Jakob of the University of Michigan, Ann Arbor. "They lose structure much like they would under high temperature. Under those circumstances, the [Hsp33] protein is specifically activated to increase resistance." Jakob emphasized that this newly discovered mechanism is clearly one way bleach kills bacteria, but it may not be the only way.

Why would bacteria have a system specifically designed to deal with bleach?

" Hypochlorous acid is an important part of host defense," Jakob said. "It's not just something we use on our countertops."

In fact, the innate immune systems of mammals, and specifically immune cells known as neutrophils, release high concentrations of hypochlorous acid (aka bleach) upon recognizing microbial invaders. In addition, Jakob said, some evidence suggests that enzymes that produce bleach may help keep the bacteria in our guts in check.

The specific effects of hypochlorous acid on proteins help to explain why hydrogen peroxide is an inferior antimicrobial agent even though both chemicals are expected to act as strong oxidants, Jakob said. Hydrogen peroxide doesn't do much for your countertops, she said, because it doesn't provoke these effects on proteins.

Hsp33 also represents another example of an emerging concept in protein biology: that some proteins actually become activated through the act of partial unfolding. Indeed, chaperones react to stress by unfolding in the same way that other proteins do. Far from leaving them useless, however, that change in conformation is exactly what turns them on. " Usually, we think proteins need structure to be active, but here they must lose structure to be active," Jakob said.

As for whether the findings will have any practical implications, Jakob said she isn't yet sure. For instance, she has doubts that bleach could be made to work any more effectively than it does, particularly given that it works so rapidly and so well as it is even at low concentrations.

The findings in bacteria could perhaps offer new insight into the damaging effects of bleach on our own proteins, she added, noting that hypochlorous acid produced by the immune system has been suspected to play a role in chronic inflammation. The protein unfolding seen in bacteria might explain what the chemical agent is doing, perhaps yielding clues about what might be done to stop it.

Source: Cell Press

Explore further: What are antioxidants? And are they truly good for us?

Related Stories

What are antioxidants? And are they truly good for us?

January 11, 2018

Antioxidants seem to be everywhere; in superfoods and skincare, even chocolate and red wine. Products that contain antioxidants are marketed as essential for good health, with promises to fight disease and reverse ageing.

Coral, human cells linked in death

June 9, 2014

Humans and corals are about as different from one another as living creatures get, but a new finding reveals that in one important way, they are more similar than anyone ever realized.

Vinegar kills tuberculosis and other mycobacteria

February 25, 2014

The active ingredient in vinegar, acetic acid, can effectively kill mycobacteria, even highly drug-resistant Mycobacterium tuberculosis, an international team of researchers from Venezuela, France, and the US reports in mBio, ...

The war on microbes

June 16, 2011

The outbreak of a new foodborne bacterial strain wreaking havoc in Germany is a reminder of the fast-changing nature of microbes and the dangers they pose to society. University of Arizona researchers are developing innovative ...

Recommended for you

Cells lacking nuclei struggle to move in 3-D environments

January 20, 2018

University of North Carolina Lineberger Comprehensive Cancer Center researchers have revealed new details of how the physical properties of the nucleus influence how cells can move around different environments - such as ...

Information engine operates with nearly perfect efficiency

January 19, 2018

Physicists have experimentally demonstrated an information engine—a device that converts information into work—with an efficiency that exceeds the conventional second law of thermodynamics. Instead, the engine's efficiency ...

New research challenges existing models of black holes

January 19, 2018

Chris Packham, associate professor of physics and astronomy at The University of Texas at San Antonio (UTSA), has collaborated on a new study that expands the scientific community's understanding of black holes in our galaxy ...

Team takes a deep look at memristors

January 19, 2018

In the race to build a computer that mimics the massive computational power of the human brain, researchers are increasingly turning to memristors, which can vary their electrical resistance based on the memory of past activity. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.