Viruses can turn harmless E. coli dangerous

Apr 16, 2009
Viruses attacking E. coli, (electron microscopy picture) Photo: Dennis Kunkel Microscopy, Inc.

For her doctorate, Camilla Sekse studied how viral DNA can be transmitted from pathogenic to non-pathogenic E. coli. Viruses that infect bacteria in this way are called bacteriophages. Her findings reveal that such transmission of bateriophage between bacteria can occur, and that in the case of E. coli it can transform a harmless bacterium into one capable of causing disease in man.

Escherichia coli is a complex group of gut that are found in all warm-blooded animals and are for the most part harmless. A few, however, cause disease in man and animals. The E. coli bacteria that produce a poison called Shiga can produce a range of effects in man. One common effect is bloody diarrhoea followed by complications such as kidney failure (haemolytic uraemic syndrome). The bacteria may be spread through or water, or from contact with animals.

A combination of qualities necessary to produce disease

A sequence of favourable circumstances needs to exist before E. coli can produce disease. The most important of these is the ability to produce Shiga toxin. The gene that codes for Shiga toxin is not innate, but is contained within bacteriophages. In other words, the bacterium needs first to be infected by a bacteriophage coding for Shiga toxin in order to produce the toxin itself.

In her work, Camilla Sekse studied E. coli O103:H25 bacteria isolated both from foodstuffs and patients from the E. coli outbreak of 2006. She and her colleagues discovered special features of these E. coli bacteria that separate them from ordinary, benign forms. This discovery lead to it being easier to demonstrate E. coli O103:H25 in suspect food products.

Dangerous bacteria in our environment

It seems that E. coli O103:H25 has existed in Norway for some time, since this bacterium was also found to be a cause of the kidney failure outbreaks both in 2003 and 2005. Studies of the entire genome of this bacterium have shown that it more closely resembles the enteropathogenic E. coli (bacteria that cause diarrhoea) than the more common, Shiga toxin-producing E. coli, namely E. coli O157:H7.

Escherichia coli bacteria that are not disease-causing can absorb and lose bacteriophages coding for Shiga toxin, and can be important in the spread of these bacteriophages in the environment, even though they don't themselves cause disease. It appears that some E. coli bacteria can both more easily absorb and lose bacteriophages that contain the gene for Shiga , and this may well be the case for E. coli O103:H25.

Provided by Norwegian School of Veterinary Science (news : web)

Explore further: Certain virus-derived genomic elements have now been shown to actively regulate important developmental processes

add to favorites email to friend print save as pdf

Related Stories

Humans not the major target of Shiga toxin

Dec 03, 2007

If you’ve survived Shiga toxin and the after-effects of food poisoning, you may have been the innocent victim of a battle for survival between predator and prey.

Researcher uncovers treatment for E.coli

Oct 29, 2008

(PhysOrg.com) -- It couldn't be more ironic. Just as the number of people in North Bay, Ont., made ill by a recent E.coli outbreak, topped 200, a University of Alberta professor has announced a breakthrough in development ...

Resistant gut bacteria will not go away by themselves

Jun 19, 2007

E. coli bacteria that have developed resistance to antibiotics will probably still be around even if we stop using antibiotics, as these strains have the same good chance as other bacteria of continuing to colonise the gut, ...

Recommended for you

Crowdsourced power to solve microbe mysteries

11 hours ago

University of New South Wales scientists hope to unlock the secrets of millions of marine microbes from waters as far apart as Sydney's Botany Bay and the Amazon River in Brazil, with the help of an international ...

Reading a biological clock in the dark

Oct 21, 2014

Our species' waking and sleeping cycles – shaped in millions of years of evolution – have been turned upside down within a single century with the advent of electric lighting and airplanes. As a result, ...

User comments : 0