Although the binding of FnBPs to fibronectin has been reported to be a strong interaction (~2.5 nN), possibly due to the fact that a single FnBP can bind up to 9 fibronectin molecules [10,11], the importance of FnBPs during infection when comparing either wild type or FnBP mutant strains in vivo has been variable. This evidence concerns the gene FN1 and infection.