Strains and Media

C.diphtheriae lysogens carrying integrated Corynebacteriophageβ toxin gene wildtype allele（strain ATCC No.13812）and CRM197 mutant allele（strain CRM-Ref.，C7（β197）tox-double lysogen）［13］，were used in the present study.Bacteria were grown on CY medium as described［13］.(https://www.daowen.com)