Azotobacter vinelandii AmrZ is a global regulator linking alginate production and c-di-GMP homeostasis

Graphical Abstract Azotobacter vinelandii AmrZ positively regulates alginate production by directly activating algD transcription and enhancing intracellular c-di-GMP accumulation, which, in turn, activates the alginate polymerization complex. Two diguanylate cyclases (DGCs) were identified as AmrZ targets, likely accounting for the reduced c-di-GMP levels observed in the absence of AmrZ. Transcription of avGReg , which encodes the main DGC during vegetative growth, was not under AmrZ control; however, post-translational regulation of AvGReg activity by AmrZ cannot be ruled out. AmrZ also positively autoregulates its own expression through an AlgU-dependent feedback loop. Finally, AmrZ positively modulates swimming motility, and our transcriptomic data suggest that this effect is indirect, occurring via its positive influence on c-di-GMP levels.