Norwich and Oxford, UK, August 18th, 2006 - Scientists at the Institute of Food Research in Norwich revealed today how the promiscuous Salmonella bacterium protects itself from getting ill after acquiring foreign DNA through “sex” with other bacteria. This discovery could lead to the design of new antibiotics to fight this killer disease. 

Salmonella causes food poisoning and kills around 1 million people worldwide every year; it is becoming more difficult to treat with drugs because it quickly evolves resistance to antibiotics by swapping genes with other bugs during “bacterial sex”. These foreign genes help the bacterium because they make it infectious and resistant to antibiotics. Professor Jay Hinton’s group at the Institute of Food Research in collaboration with Oxford Gene Technology, have discovered that a protein called H-NS switches off these incoming genes until they need to be activated - a process called gene silencing. This study, published today in the respected online journal PLoS Pathogens shows that without proper control the incoming genes make proteins that are toxic for the bacterium. Without H-NS, the bacterium has problems growing and can’t function properly. H-NS allows the bacteria to evolve by determining how new pieces of DNA are used in Salmonella.  

“We may have found the Achilles’ Heel for Salmonella bacteria because they need this H-NS protein to acquire new skills and become infectious” says Jay Hinton, “Salmonella still kills a huge number of people. Discoveries like this will help us find new ways of attacking these dangerous bacteria; if we can inactivate H-NS, we could discover urgently-needed new antibiotics.” 

Hinton’s team found that H-NS works by coating stretches of the foreign DNA, which can be distinguished from Salmonella DNA because it contains a higher amount of the molecules adenine and thymine (A and T). H-NS binding stops foreign genes producing protein unnecessarily. Once the bacterium has invaded a human, the effect of H-NS is blocked and the genes can be switched on.  

"Gene silencing is well known in plants and animals, but has never been seen before in bacteria” Jay Hinton adds, "It looks like H-NS has helped Salmonella to evolve to infect humans over the last 10 million years." 

The researchers hope that this discovery could lead to a new strategy in the fight against drug-resistant “superbugs”. 

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Notes for Editors

• For more information, please contact Vicky Just to provide images and arrange interviews: +44 (0)1603 255111, victoria.just@bbsrc.ac.uk  
• This work is published in the online journal PLoS Pathogens ( http://pathogens.plosjournals.org/  ).
• The mission of the Institute of Food Research (www.ifr.ac.uk) is to undertake international quality scientific research relevant to food and human health and to work in partnership with others to provide underpinning science for consumers, policy makers, the food industry and academia. It is a company limited by guarantee, with charitable status, grant aided by the Biotechnology and Biological Sciences Research Council (www.bbsrc.ac.uk).

·         The researchers determined the location of H-NS binding to the Salmonella DNA using customised ChIP (Chromatin Immunoprecipitation) microarrays developed by Oxford Gene Technology.

·         Oxford Gene Technology (http://www.ogt.co.uk/) was founded in 1995 by the pioneer of Southern Blotting, Professor Sir Edwin Southern. OGT operates out of Begbroke Business Park near Oxford, with good access to a growing network of life science companies. The key focus areas of OGT include:

• Array-based application products and services for life science research and molecular diagnostics.
• Development of innovative platform products for clinical research and diagnostics.
• Licensing, particularly in the area of microarrays.
• Scientific collaborations to generate diagnostic biomarker intellectual property.
• PLoS is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. www.plos.org
  
   

Salmonella Facts:

• Salmonella food poisoning costs the British economy about £1 billion a year and the US economy almost US$4 billion.
• Since the beginning of the 1990s, strains of Salmonella enterica sv. Typhimurium resistant to a range of antibiotics have emerged and are threatening to become a serious public health problem, particularly in developing countries.
• Since 1885, a total of 2213 types of salmonella have been identified. They vary in the severity of illness they cause.
• Symptoms of salmonellosis (food poisoning caused by Salmonella) are fever, headache, abdominal pain, diarrhoea, nausea and vomiting, and are usually self-limiting after a week. In some cases, particularly in the young and very elderly, dehydration can become severe and life threatening.
• Salmonella Typhimurium can be found in a broad range of animals, birds and reptiles as well as the environment. It causes food poisoning in humans mainly through the consumption of raw or undercooked contaminated food of animal origin - especially poultry, eggs, meat, salad vegetables and milk.

 

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