Strain-dependent motility defects and suppression by a flhO mutation for B. subtilis bactofilins.

Extending this work, we show that motility defects vary between different B. subtilis strains, with strain 168 showing no defect in motility, and 3610 showing delayed induction of swimming. Generation of single gene deletions in PY79 was possible by transferring corresponding deletions from 168. In the natural isolate 3610, gene deletions also showed a negative effect on biofilm formation, revealing an additional function for BacE and BacF. A spontaneous arising suppressor mutation in PY79 was mapped to the flhO gene, a constituent of the flagellum, which obtained an 18 amino acid extension at its C-terminus. Our findings show that bactofilin gene deletions lead to different motility phenotypes dependent on the strain background, and affect biofilm formation in the natural isolate 3610. Our data reinforce the idea of a connection between bactofilins and motion via the flagellum, and suggest that they operate in a switch like manner.