title: NADH dehydrogenase deficiency results in low respiration rate and improved aerobic growth of Zymomonas mobilis.
abstract: The respiratory chain of the ethanol-producing bacterium Zymomonas mobilis is able to oxidize both species of nicotinamide cofactors, NADH and NADPH. A mutant strain with a chloramphenicol-resistance determinant inserted in ndh (encoding an NADH : CoQ oxidoreductase of type II) lacked the membrane NADH and NADPH oxidase activities, while its respiratory D-lactate oxidase activity was increased. Cells of the mutant strain showed a very low respiration rate with glucose and no respiration with ethanol. The aerobic growth rate of the mutant was elevated; exponential growth persisted longer, resulting in higher biomass densities. For the parent strain a similar effect of aerobic growth stimulation was achieved previously in the presence of submillimolar cyanide concentrations. It is concluded (i) that the respiratory chain of Z. mobilis contains only one functional NAD(P)H dehydrogenase, product of the ndh gene, and (ii) that inhibition of respiration, whether resulting from a mutation or from inhibitor action, stimulates Z. mobilis aerobic growth due to redirection of the NADH flux from respiration to ethanol synthesis, thus minimizing accumulation of toxic intermediates by contributing to the reduction of acetaldehyde to ethanol.
authors.affiliation: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
authors.forename: Uldis
authors.initials: U
authors.lastname: Kalnenieks
authors.affiliation: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
authors.forename: Nina
authors.initials: N
authors.lastname: Galinina
authors.affiliation: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
authors.forename: Inese
authors.initials: I
authors.lastname: Strazdina
authors.affiliation: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
authors.forename: Zane
authors.initials: Z
authors.lastname: Kravale
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: James L
authors.initials: JL
authors.lastname: Pickford
authors.affiliation: Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
authors.forename: Reinis
authors.initials: R
authors.lastname: Rutkis
authors.affiliation: Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Poole
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism; D000332:Aerobiosis / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D018533:Biomass; D002462:Cell Membrane / Q000201:enzymology; D000431:Ethanol / Q000378:metabolism; D017353:Gene Deletion; D005947:Glucose / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D016254:Mutagenesis, Insertional; D009243:NAD / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D017355:Zymomonas / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D009243:NAD; D000431:Ethanol; D009249:NADP; D006899:Mixed Function Oxygenases; C021497:lactate 2-monooxygenase; D009245:NADH Dehydrogenase; D000079:Acetaldehyde; D005947:Glucose; D010100:Oxygen