Growth characteristics of FMDVs in BHK-21 cells. A Plaque morphologies of the mutant viruses and wt virus. Monolayers were infected with tenfold serial dilutions of rHN/TURVP1, rHN/TURVP1 and rHN. After 1 h of adsorption, infected cells were overlaid with 0.6% gum tragacanth. The cells were fixed, stained and photographed at 48 h post-infection. B One-step growth curves for the mutant viruses and the wt virus. Monolayers were infected with rHN/TURVP1, rHN/TURVP1 and rHN (5 moi), and samples were analysed at 4, 8, 12, 16 and 20 hpi. The results were obtained from three individual experiments.