05 August 2010

Bad Bacteria and Their Harmless Kin Share, Swap Genes

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The genetic make-up of pathogenic bacteria and their harmless cousins is much more similar than previously thought, UA microbiologists find.

In the bacterial world, good guys can potentially turn into bad guys and vice versa - just by swapping genes, microbiologists at the University of Arizona have discovered.

The researchers studied bacteria belonging to the genus Neisseria. These bacteria colonize the mucous membranes of humans.

Intrigued by the question of why some species of Neisseria are commensals - harmless colonizers whose presence in the body goes unnoticed - while others cause disease, the team identified the complete genetic codes of eight species of commensal Neisseria and compared them to the published genomes of the two known pathogenic species that cause gonorrhea and meningitis.

"The gene content of Neisseria species is fluid and not etched in stone," said team leader Magdalene So, who is a professor in the UA's department of immunobiology, where she directs the Microbial Pathogenesis Program. She also is a member of the UA's BIO5 Institute.

"These bacteria have the capacity to acquire new genes and drop others frequently," So said.

The study marks the first time scientists have determined the total gene content of a large group of related commensal bacteria and systematically compared it with the genomes of related pathogens. So's team reports its findings in Public Library of Science Online, or PLoS One.

To their surprise, the researchers found no clear genetic demarcation between commensal and pathogenic Neisseria. In fact, many commensals have the same genes known to promote virulence (the capacity to cause disease) in the two pathogens.

(Innovations Report)

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