The Na+-translocating NADH : ubiquinone oxidoreductase of Azotobacter vinelandii negatively regulates alginate synthesis.
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 ( approximately 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.
Núñez
Cinthia
C
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
Bogachev
Alexander V
AV
Department of Molecular Energetics of Microorganisms, A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia.
Guzmán
Gabriel
G
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
Tello
Isaac
I
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
Guzmán
Josefina
J
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
Espín
Guadalupe
G
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
D000464:Alginates / Q000378:metabolism*; D016948:Azotobacter vinelandii / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D011808:Quinone Reductases / Q000235:genetics / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D014451:Ubiquinone
D000464:Alginates; D004251:DNA Transposable Elements; D014451:Ubiquinone; D012964:Sodium; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases