FIGURE 4.

Deletion of eight extracellular protease genes in B. subtilis. (A) The chromosome structure of wild type strain (B. subtilis 168) and the deletion mutants of protease genes. The squared N and C indicate 500 bp donor DNA of each N- and C-terminus. The arrows indicate primer binding regions. (B) PCR analysis for confirming the deletion of each extracellular protease gene, using primer sets NF1/CR1. 1 indicates a wild type strain and 2 indicates strain BS-D126. Expected sizes of PCR products are 1.5 and 1.0 kb from wild type and mutant, respectively. (C) The mutation (gray) and curing (white) efficiencies of each mutant strain. The bars display the means of three independent experiments, with the error bars indicating standard deviations.