Functions as both a transcriptional activator and repressor of multiple genes encoding virulence factors as well as genes involved in environmental adaptation. Represses genes involved in iron homeostasis (PubMed:24670089, PubMed:29386661). Modulates intracellular levels of c-di-GMP which in turn regulates swimming motility and biofilm formation (PubMed:29386661). Deletion shows increased swimming motility, decreased biofilm formation and very limited ability for competitive colonization of rhizosphere.