Outer membrane-associated serine protease of intestinal spirochetes.

Pathogenic intestinal spirochetes cause damage to the intestinal mucosa of humans and animals by an unknown mechanism. The purpose of this study was to assess the pathogenic intestinal spirochetes Serpulina hyodysenteriae, Serpulina pilosicoli, and Brachyspira aalborgi and the non-pathogenic commensal intestinal spirochetes Serpulina innocens and Treponema succinifaciens for protease activity. A partially heat stable, subtilisin-like, serine protease was identified in the outer membrane of all spirochetes and thus may be essential for survival in the intestinal environment. The outer membrane protease may indirectly contribute to intestinal damage caused by pathogenic spirochetes during association with the mucosal surface of the host.