An environmentally regulated pilus‐like appendage involved inCampylobacterpathogenesis

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Abstract
Summary: Examination of strains ofCampylobacter jejuni, Campylobacter coli, andCampylobacter fetusby electron microscopy revealed that they produced peritrichous pilus‐like appendages when the bacteria were grown in the presence of bile salts. Various bile‐salt supplements were used and it was found that deoxycholate and chenodeoxycholic acid caused a significant enhancement of pilus production and resulted in a highly aggregative phenotype. Morphologically, the pili were between 4 and 7 nm in width and were greater than 1 μm in length. A gene, termedpspA, which encodes a predicted protein resembling protease IV ofEscherichia coli, was identified inC. jejunistrain 81–176. A site‐specific insertional mutation within this gene resulted in the loss of pilus synthesis as determined by electron microscopy. Insertions upstream and downstream of the gene had no effect on pilus production. The non‐piliated mutant of strain 81–176 showed no reduction in adherence to or invasion of INT 407 cellsin vitro. However, this mutant, while still possessing the ability to colonize ferrets, caused significantly reduced disease symptoms in this animal model.