In order to prepare a solid medium, agar was added at a concentration of 1.5%. Agar medium (AG) contained only 15 g/l
agar powder. LB was diluted 10–106 times to prepare 1/10–1/106 LB medium, and named 1/10 LB or 1/106 LB. The media were sterilized at 121C for 20 min.