FIG. 1.

Model for control of phenazine production in P. aureofaciens 30-84. GacS responds to the presence of an unknown signal by transphosphorylating GacA. GacA controls phenazine production by regulating AHL synthesis through transcriptional control of phzI either directly or indirectly (reaction a). GacA also controls phenazine production at a second level, possibly by direct binding of GacA (reaction b) or by some unidentified regulatory protein controlled by GacA (reactions c). The solid arrows indicate known regulatory controls, and the dashed arrows indicate possible regulatory controls. Places where positive and negative regulation occur are indicated by plus and minus signs, respectively.