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November 14, 2008, 3:55 pm

How bleach kills bacteria

Bleach is used in houses around the world to clean, killing the bacteria, especially in bathrooms and kitchens. But what is the active molecule in bleach and how are the bacteria killed? Now scientists can explain.


The active ingredient in bleach is hypochlorous acid, HOCl - read more about it here.

Its reactions with amino acids which have amino or sulphidryl side chains have already been reported.

This new work shows that HOCl makes important bacterial proteins unfold, losing the shape which is important for them to work properly . A protein that has lost its shape is said to be 'denatured'.

Once the bacterial proteins are denatured by the HOCl, they stick together (called aggregation) and the bacterial cell dies.

Amazingly, some bacteria can protect themselves from the effects of HOCl using a molecule called Hsp33.

Heat can also denature proteins - think of what happens when you heat egg white! Hsp33 is a Heat Shock Protein, produced in times of heat stress to protect the bacteria's proteins from destruction by heat. Heat shock proteins are found in many living organisms, from bacteria to humans!

Read a summary of the original scientific article in the journal Cell.

Greek translated article here.  


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