The Na+-translocating NADH : ubiquinone oxidoreductase of Azotobacter vinelandii negatively regulates alginate synthesis Núñez, Cinthia and Bogachev, Alexander V. and Guzmán, Gabriel and Tello, Isaac and Guzmán, Josefina and Espín, Guadalupe,, 155, 249-256 (2009), doi = https://doi.org/10.1099/mic.0.022533-0, publicationName = Microbiology Society, issn = 1350-0872, abstract= Azotobacter vinelandii is a nitrogen-fixing soil bacterium that produces the exopolysaccharide alginate. In this report we describe the isolation and characterization of A. vinelandii strain GG4, which carries an nqrE : : Tn5 mutation resulting in alginate overproduction. The nqrE gene encodes a subunit of the Na+-translocating NADH : ubiquinone oxidoreductase (Na+-NQR). As expected, Na+-NQR activity was abolished in mutant GG4. When this strain was complemented with the nqrEF genes this activity was restored and alginate production was reduced to wild-type levels. Na+-NQR may be the main sodium pump of A. vinelandii under the conditions tested (∼2 mM Na+) since no Na+/H+-antiporter activity was detected. Collectively our results indicate that in A. vinelandii the lack of Na+-NQR activity caused the absence of a transmembrane Na+ gradient and an increase in alginate production., language=, type=