Extra-chromosomal DNA maintenance in Bacillus subtilis, dependence on flagellation factor FliF and moonlighting mediator EdmS

• EdmS is a unique mediator of extra-chromosomal DNA maintenance (EDM) in Bacillus subtilis.
• Mutation of global regulator SwrA abolished EdmS-mediated EDM in B. subtilis.
• Analysis of B. subtilis fla/che-deletion mutants identified an EDM cooperator, FliF.
• This is the first report of the moonlighting function of FliF in DNA maintenance.

Extra-chromosomal DNA maintenance (EDM) as an important process in the propagation and genetic engineering of microbes. Bacillus subtilis EdmS (formerly PgsE), a protein comprising 55 amino acids, is a mediator of the EDM process. In this study, the effect of mutation of global regulators on B. subtilis EDM was examined. Mutation of the swrA gene abolished EdmS-mediated EDM. It is known that swrA predominantly regulates expression of the fla/che operon in B. subtilis. We therefore performed EDM analysis using fla/che-deletion mutants and identified an EDM-mediated EDM cooperator in the flgB–fliL region. Further genetic investigation identified the flagellation factor FliF is a crucial EDM cooperator. To our knowledge, this is the first observation of the moonlighting function of FliF in DNA maintenance.