Growth conditions for the expression of fibronectin and collagen binding to Salmonella

Binding of ¹²⁵I-fibronectin, its ¹²⁵I-labelled 29-kDa aminoterminal fragment, and ¹²⁵I-collagen to cells of 13 Salmonella strains grown in broth and agar media at three different temperatures was studied. Of the 13 strains, 7 had only smooth colony morphologies while three strains were pairs of both smooth strains and their corresponding rough variants. The three rough variants showed higher binding to fibronectin, it's 29-kDa fragment and to collagen, than the corresponding smooth forms. However, the percentage of ¹²⁵I-protein bound was greatly influenced by the growth conditions. In these three pairs of strains, there was a direct correlation between cell-surface hydrophobicity and the binding activity, but this correlation was not observed in the remaining strains. Thus, some of the strains showed high cell-surface hydrophobicity but low binding activity under optimal growth conditions. The highest binding rates of fibronectin and of it's 29-kDA fragment were obtained with bacteria grown on colonisation factor antigen (CFA) agar at 33 °C, while the binding to collagen was slighly higher when bacteria were cultured on tryptic soy agar.