Electron microscopy of zoocin A-treated sensitive streptococcus cells revealed cytoplasmic disruption and ultimately complete rupture of the cell wall. Culture viability and optical density were shown to decrease rapidly and simultaneously in Streptococcus pyogenes FF22 but less quickly in the relatively more resistant Streptococcus mutans 10449. Zoocin A was shown to cleave hexaglycine in a colorimetric cell-free microtiter assay system, and it is concluded that the killing action of zoocin A, like that of lysostaphin, is most probably the result of direct cleavage of the peptidoglycan cross-links in the cell wall. The relationship between sensitivity to zoocin A and the peptidoglycan cross-linkage structure of Streptococcus zooepidemicus, Lactococcus spp., S. pyogenes, Streptococcus gordonii, Streptococcus oralis, S. mutans, and Streptococcus rattus has been evaluated.

Recently, the term MSCRAMM (microbial surface components recognizing adhesive matrix molecules), has been introduced to describe microbial molecules that recognize extracellular matrix (ECM) [1]. Here we present evidence for the presence of fibronectin-binding molecules in Borrelia burgdorferi and several other Borrelia species. Immunofluorescence studies show that plasma fibronectin is bound uniformly over the cell surface of free swimming B. burgdorferi. In addition, the spirochetes are able to bind to plasma fibronectin-coated microwell plates, an interaction that is inhibited by anti-fibronectin antibody as well as exogenous plasma fibronectin. Taken together, the data suggest that fibronectin binds to the surface of the spirochete. On Western blot-like assays, B. burgdorferi and some B. afzelii strains express a major fibronectin-binding protein (Fn-BA) with an approximate molecular mass of 52 kDa. In addition, several other major Fn-BAs were found in B. hermsii (26, 31, 33, 39, 46, 54 and 58 kDa) and B. turicatae (39, 41, 45, 50, 56, 59 and 66 kDa). Preliminary evidence suggests that fibronectin (and Fn-BA) may play a role as a molecular bridge between the spirochete and other components of the extracellular matrix.

Lyme disease is a multisystemic disorder caused by Borrelia burgdorferi, an invasive spirochete. B. burgdorferi has a predilection for collagenous tissue and one major clinical manifestation of the disease is arthritis. We have identified a collagenolytic activity in B. burgdorferi detergent lysates using iodinated gelatin as well as iodinated pepsinized human collagen types II and IV as protein substrates. In addition, we describe several proteolytic activities in B. burgdorferi with molecular masses greater than 200 kDa on sodium dodecyl sulfate polyacrylamide gels containing copolymerized gelatin. We propose that the collagenolytic activity of B. burgdorferi has a role in invasion, in the pathogenesis of Lyme arthritis, and perhaps also in other manifestations of Lyme borreliosis.