Fig. 1

Schematic illustration of quorum sensing interactions in Bacillus. The figure is limited to the interactions that are addressed in this work. The upper part shows the influence of the deletion of Rap-phosphatases on the quorum sensing mechanism. The deletion is indicated in light gray. For simplification all Rap-phosphatases have been highlighted, although they were deleted individually in this work. In absence of the respective Rap-phosphatase, its inhibitory effect on the DNA-binding capacity of response regulator ComA is impaired (indicated by a dashed line). This means that the Rap-phosphatases should be “inactive” (strains CT10–CT12) and it is presumed that surfactin production is increased here. The lower part of the figure represents the negative control CT5, which carries a oppA deletion. Due to this deletion, the ABC transporter Opp should become non-functional. This is again highlighted in light gray. The Phr peptides responsible for Rap-phosphatase inhibition can therefore not be transported into the cell (indicated by a dashed line). Oppression of Rap-phosphatases should not be present in this case and therefore all Rap-phosphatases should be “fully active” (indicated in dark gray). For the negative control, it is assumed that surfactin production should be decreased. The hypotheses are supported by the literature, as described in the text. For an overview of molecular interactions, see Perego (2013)