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Monday, August 30, 2010

Corkscrew shape required for H. pylori infection

Helicobacter pylori are the corkscrew-shaped bacteria that cause ulcers and most stomach cancers. Although scientists suspected that the shape of the bacteria played a crucial role, that hypothesis was only recently proven by Nina Salama and her colleagues from the University of Washington, Yale University, Newcastle University and the Fred Hutchinson Cancer Research Center.

Salama and her team identified four genes responsible for creating the typical helical shape of H. pylori. These proteins snip the bacterial cell wall in strategic places, allowing the stiff rod-shaped cell wall to twist into a helix. Mutants lacking any one of the genes were unable to twist into proper shapes, and more importantly, were unable to colonize mouse stomachs.

At first, the researchers assumed that the mutant bacteria were having trouble pushing their way through the thick gelatin-like mucus that coats stomachs. However, the odd-shaped bugs had no trouble propelling themselves through comparable amounts of gel in Petri dishes. It is unclear why the twisted shape is critical for infection. In any case, microbiologists hope to use the shape-changing genes as drug targets, especially as several other disease-causing pathogens, such as Vibrio cholerae (cholera), and Campylobacter jejuni (bacterial diarrhea) have the same proteins.