FIG. 1.

Secreted proteases are required for swarming motility by B. subtilis A164. Swarm motility of B. subtilis A164 (A) and A164 mutants A164Δ5, MBin7, A164Δ8, and A164Δ10 (clockwise from left) (B) is shown. The absence of surfactin production in A164Δ5 and A164Δ8 results in a less-robust swarming phenotype, and a nonswarming phenotype is exhibited by A164Δ10, which is deficient in both surfactin and protease activity. Although MBin7 appears to have a nonswarming phenotype, swarming is initiated after 48 h for this strain and is not completely inhibited until deletions are made in the remaining extracellular protease, aprE, and sigF (MBin10 strain, data not shown). All strains were inoculated with a toothpick onto a 0.7% agar LB swarm plate and incubated for 20 h at 37°C.