AmyK38 production by multiple-deletion strains of B. subtilis. B. subtilis strains 168 (a), MGB625 (b), MGB723 (c), and MGB874 (d) harboring pHYK38 were cultured in 2xL-Mal medium with shaking at 30°C. Culture OD600 (open circles) and α-amylase activity in the growth medium (black bars) were evaluated. Strain 168 is a wild-type strain and strains MGB625, MGB723, and MGB874 are multiple-deletion mutants. The size of the genomic deletions increases in the order MGB625, MGB723, and MGB874. The results presented are the means of three individual experiments. Error bars represent standard deviations (n = 3).