B. subtilis was prepared as a cell suspension (approximately1 108 colony-forming units (CFU)/ml, measured by hemocytometer) by washing cultures grown for 24 h at 37 C on nutrient agar (NA; 20 g glucose, 5 g yeast extract,10 g peptone, 5 g NaCl,15 g agar, 1 l distilledwater [pH 6.5e6.7]) with sterile distilledwater and then
adjusting them to the desired cell density.