Extensive research has shown that Borrelia burgdorferi, the bacterium that causes Lyme disease, uses ticks for dissemination to mammalian hosts.
An article in the 19 December issue of PLOS Pathogens identifies HrpA, an RNA helicase, as a crucial player in the transmission from ticks to mammals.
George Chaconas, from the University of Calgary, Canada, and a member of the university's Snyder Institute for Chronic Diseases, and colleagues had previously identified HrpA as a modulator of B. burgdorferi protein expression. For this study, Chaconas' group joined forces with Justin Radolf and Melissa Caimano from the University of Connecticut Health Center, USA, to analyze the molecular function of the HrpA protein and further explore its role in the bacterium's complicated life cycle, in particular for transmission of the pathogen.
When the scientists tested whether mutant B. burgdorferi that lacked the hrpA gene could infect mice, they found that the mutant bacteria could not. For this experiment, the scientists injected normal or mutant bacteria directly into mice, and subsequently tested mouse blood, skin, bladder, or joint tissue for the presence of bacteria. Normal bacteria could be recovered from all tissues after a week and up to 4 weeks post injection, but mutant bacteria were undetectable even after one week, suggesting that they were unable to survive or multiply in the mammalian host.