The Role of the ncRNA RgsA in the Oxidative Stress Response and Biofilm Formation in Azotobacter vinelandii.

Azotobacter vinelandii is a soil bacterium that forms desiccation-resistant cysts, and the exopolysaccharide alginate is essential for this process. A. vinelandii also produces alginate under vegetative growth conditions, and this production has biotechnological significance. Poly-β-hydroxybutyrate (PHB) is another polymer synthetized by A. vinelandii that is of biotechnological interest. The GacS/A two-component signal transduction system plays an important role in regulating alginate production, PHB synthesis, and encystment. GacS/A in turn controls other important regulators such as RpoS and the ncRNAs that belong to the Rsm family. In A. vinelandii, RpoS is necessary for resisting oxidative stress as a result of its control over the expression of the catalase Kat1. In this work, we characterized a new ncRNA in A. vinelandii that is homologous to the P16/RsgA reported in Pseudomonas. We found that the expression of rgsA is regulated by GacA and RpoS and that it was essential for oxidative stress resistance. However, the activity of the catalase Kat1 is unaffected in rgsA mutants. Unlike those reported in Pseudomonas, RgsA in A. vinelandii regulates biofilm formation but not polymer synthesis or the encystment process.