Structural studies of a toxin from Bacillus cereus that causes diarrhea

Jan 04, 2013
The Bacillus cereus strain NVH 0075/95 which is producing the Nhe toxin. Scanning electron microscopy. Credit: Danh Phung

Food poisoning caused by Bacillus cereus can lead to diarrhea which is probably caused by a 3-component toxin which is produced by this bacteria strain and which perforates and kills cells.

New doctoral research has revealed one of the protein structures of this toxin and has led to a better understanding of the mechanisms behind multi-component, pore-forming toxins. These findings can enhance food safety.

Bacteria produce toxins in order to defend themselves and to gain nourishment. Pore-forming toxins make up about a third of all . These toxins kill cells by making holes in the cell walls, so causing leakages and swelling which in turn leads to the disintegration of the cells. The most common pore-forming toxins consist of one protein and in some special cases, of two proteins.

Toxins which consist of three proteins (3-component) are extremely rare. The bacterium Bacillus cereus produces two such 3-component toxins. One of them is non-hemolytic enterotoxin, also known as Nhe. It is believed that this toxin is the major food poisoning toxin produced by B. cereus. It is found in all B. cereus strains that cause food poisoning and in nearly all other B. cereus strains. The three proteins in the Nhe toxin are called NheA, NheB and NheC.

In the course of her doctoral research, Danh Phung discovered the of one of the proteins in the Nhe toxin: NheA. This protein is the least studied of this toxin complex, but its presence is essential in order to achieve full cellular toxicity and . Phung's study is also the first to show that the Nhe proteins form structures resembling pores.

Structural studies of a toxin from Bacillus cereus that causes diarrhea

The way the Nhe toxin works is not fully understood. Phung showed that NheB, which is believed to be the most important protein in this toxin complex, forms pore-like structures of itself and produces large amounts of molecules by means of an artificial , for example a lipid. These findings indicate that the NheB protein undergoes structural changes before the pore-forming process, which involves the other Nhe-proteins, begins.

Danh Phung carried out her doctoral research at the Norwegian School of Veterinary Science in collaboration with the Sir Hans Krebs Institute at the University of Sheffield in the UK.

M.Sc. Danh Phung defended her doctoral research on 18th December 2012 at the Norwegian School of Veterinary Science (NVH) with a thesis entitled "Structure and mode of action on the Nhe enterotoxin from ".

Explore further: Life's extremists may be an untapped source of antibacterial drugs

add to favorites email to friend print save as pdf

Related Stories

Targeting toxin trafficking

Jul 21, 2011

Toxins produced by plants and bacteria pose a significant threat to humans, as emphasized by the recent effects of cucumber-borne Shiga toxin in Germany. Now, new research published on July 21st by the Cell Press journal ...

Bacteria poison themselves from within

Mar 23, 2011

(PhysOrg.com) -- The research group led by Anton Meinhart at the Max Planck Institute for Medical Research in Heidelberg has shown that proteins from the zeta toxin group trigger a self-destructive mechanism ...

X-rays reveal the self-defence mechanisms of bacteria

Sep 14, 2012

A research group at Aarhus University has gained unique insight into how bacteria control the amount of toxin in their cells. The new findings can eventually lead to the development of novel forms of treatment ...

Recommended for you

Cohesin molecule safeguards cell division

Nov 21, 2014

The cohesin molecule ensures the proper distribution of DNA during cell division. Scientists at the Research Institute of Molecular Pathology (IMP) in Vienna can now prove the concept of its carabiner-like ...

Nail stem cells prove more versatile than press ons

Nov 21, 2014

There are plenty of body parts that don't grow back when you lose them. Nails are an exception, and a new study published in the Proceedings of the National Academy of Sciences (PNAS) reveals some of the r ...

Scientists develop 3-D model of regulator protein bax

Nov 21, 2014

Scientists at Freie Universität Berlin, the University of Tubingen, and the Swiss Federal Institute of Technology in Zurich (ETH) provide a new 3D model of the protein Bax, a key regulator of cell death. When active, Bax ...

Researchers unwind the mysteries of the cellular clock

Nov 20, 2014

Human existence is basically circadian. Most of us wake in the morning, sleep in the evening, and eat in between. Body temperature, metabolism, and hormone levels all fluctuate throughout the day, and it ...

User comments : 0

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.