The effect of growth temperature on Staphylococcus aureus binding to type I collagen

Many strains of Staphylococcus aureus produce a collagen-binding surface protein that could enable these strains to colonize tissues such as bone. Previous studies indicated that the expression of the collagen receptor varies with growth conditions. We report here that the growth temperature influences the ability of some S. aureus strains to produce this receptor. S. aureus isolates from human, osteomyelitic bone were grown at 37°C and 42°C and tested for agglutination of collagen-coated latex beads. Binding by 42°C grown cells was significantly reduced in five of the seven isolates studied, including a complete loss of collagen binding in three of these isolates. In an 125I-collagen-binding assay, the binding ability of one of these isolates, strain #16, was 20-fold lower if grown at 42°C. Reduced collagen binding by this isolate could be demonstrated after only two cell divisions at 42°C and the cells regained the ability to bind collagen when shifted back to 37°C. Sodium dodecyl sulfate (SDS)-PAGE confirmed the presence of proteins at 117 kDa in strain #16 and 135 kDa in SMH which were absent following growth at 42°C. Chicken IgG, specific for the 117 kDa protein, was found to react in immunoblot assays with these proteins as well as a protein of 135 kDa extracted from S. aureus Cowan 1. The antibody did not react with proteins extracted from non-binding strains. Strains #15 and #21, collagen-binders at both 37°C and 42°C, produced immunoreactive proteins at 110 and 135 kDa, respectively, in lysates from cells grown at both temperatures. Antibody against a recombinant form of a previously characterized collagen receptor was used to confirm cross reactivity with these novel collagen receptors. These data suggest that the ability to produce the collagen receptor is temperature sensitive in some S. aureus strains associated with osteomyelitis. It is proposed that a better understanding of the environmental effects on collagen receptor production could enhance our understanding of staphylococcal infections in bone and joints.