FIG. 3.

Ribozyme expression from the nisin promoter: autoradiogram of Northern hybridization blot showing levels of δRz-E196 expression in different L. lactis strains. Cells were diluted from fresh overnight cultures and grown to an OD₆₀₀ of 0.5, and ribozyme expression was induced with nisin for 1 h. Strains NZ9800, NZ9000, and NZ3900 contain a unique chromosomal copy of both the nisK and nisR genes and trigger expression of δRz-E196 from the nisin promoter (PnisA). Control strain IL1403 lacks the nisK and nisR genes. The pMSP3535 plasmid carries nisK and nisR, which allows gene expression from the nisin promoter in IL1403. Levels of ribozyme expression were normalized against the amount of 5S rRNA, and then the levels in different strains were compared using the amount of fully processed δRz-E196 produced in IL1403 as the basal level (1×).