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25 August, 2006 - 16:24 By Staff Reporter

‘Bonking bugs’ rumbled by researchers

A killer bug that develops its resistance to antibiotics during the bacterial equivalent of sex is about to get its ‘come-uppance.’

The bonking bugs have been rumbled by Norwich scientists. Researchers at the Institute of Food Research have discovered that sexed-up Salmonella build immunity to antibiotics by swapping genes during ‘bacterial sex.’

Now the orgasmic organisms will have their libido lopped in the lab.

The IFR team says the promiscuous parasite uses a protein called H-NS to protect itself from toxic effects after acquiring foreign DNA through sex with other bacteria. Blocking this protein could provide a new route to designing urgently needed antibiotics to fight the killer disease.

Salmonella causes food poisoning and kills around a million people worldwide every year but is becoming more difficult to treat with drugs.

Professor Jay Hinton’s group at the Institute of Food Research, in collaboration with Oxford Gene Techn-ology, have discovered that the H-NS protein switches off incoming genes during sexual fusion until they need to be activated – a process called gene silencing.

The new study, published in the 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 Prof 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” says Prof Hinton. “It looks like H-NS has helped Salmonella to evolve to infect humans over the last 10 million years.”

The researchers hope their discovery will trigger a new strategy.

Salmonella food poisoning costs the UK economy about £1bn a year and the US almost $4bn.

Since the start 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.




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