Inducible resistance against nisin in Lactobacillus casei

Most strains of Lactobacillus casei tested were found to be nisin-resistant. The addition of nisin to a growing culture of a resistant strain stopped growth for several hours; however, growth then resumed at the previous rate. Nisin induced a resistance mechanism that was lost by one passage in nisin-free medium. During induction with nisin, the cells produced an anionic, phosphate containing polysaccharide with the subunits rhamnose and galactose. This polysaccharide protected sensitive cells of L. casei against the bactericidal action of nisin.