MeeY and YybP, two proteins regulated by manganese-sensing riboswitches, are required for Bacillus subtilis biofilm formation

In the rhizosphere, Bacillus subtilis forms biofilms on plant roots and contributes to improved plant growth and disease resistance. Manganese stimulates biofilm formation in B. subtilis 3610, but the underlying mechanism is unknown. Here, we show that YybP and MeeY (formerly YkoY), two proteins regulated by the eponymous manganese-sensing yybP-ykoY riboswitches, are required for biofilm formation. MeeY is a TerC family membrane protein implicated in manganese export and YybP is of unknown function. Inactivation of either meeY or yybP leads to reduced synthesis of matrix-associated exopolysaccharide and a loss of biofilm-associated divalent cations.

Deletion of sinR restores exopolysaccharide but does not restore normal metalation of the biofilm matrix. We conclude that the YybP and MeeY membrane proteins are previously unappreciated regulators of biofilm formation important for the production and metalation of exopolysaccharide.