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Sex decides how bacteria become drug-resistant?

Posted on May 02 2014 | IANS

London, May 2 : The secret to how bacteria evade vaccines and rapidly become drug-resistant may lie in 'recombination' - the bacterial substitute for sex - a study has found.

Although bacteria do not have sex as such, they can mix their genetic material by pulling in DNA from dead bacterial cells and inserting these into their own genome.

The recombination process, or the bacterial substitute for sex, may be more complex than previously thought, showed the findings.

"During recombination, bacteria might incorporate new DNA which makes them resistant to treatments, or they may take on genes which change their surface structure, enabling them to evade vaccines," said Rafal Mostowy of Imperial College London.

"This is a major step forward in our understanding of how recombination can result in bacteria evading vaccines and acquiring resistance to antibiotics," Mostowy added.

The researchers studied two 'lineages' of the bacterium Streptococcus pneumoniae (known as pneumococcus), one of which is resistant to drugs.

Pneumococcus is one of the major causes of pneumonia, meningitis and septicaemia.

Using DNA sequences of bacteria strains collected over 36 years, the researchers were able to reconstruct an evolutionary tree for two 'lineages', mapping when new DNA had been taken on board and how the bacteria had evolved as a result.

Although recombination has always been thought of as a uniform process, the models showed two distinct types of recombination - micro and macro.

In 'micro-recombination', the bacteria regularly incorporate small amounts of DNA that make little difference to their genome.

Although 'macro-recombination' takes place less frequently, it involves the bacteria taking on large amounts of DNA which make a significant change to the genome.

The scientists found that recombination took place frequently in the evolution of the more resistant lineage they studied, and less frequently in the less resistant lineage.

The study appeared in the journal PLoS Genetics.

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