NADH dehydrogenase deficiency results in low respiration rate and improved aerobic growth of Zymomonas mobilis.
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.
Kalnenieks
Uldis
U
Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
Galinina
Nina
N
Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
Strazdina
Inese
I
Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
Kravale
Zane
Z
Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
Pickford
James L
JL
Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
Rutkis
Reinis
R
Institute of Microbiology and Biotechnology, University of Latvia, Kronvalda Boulv. 4, LV-1586, Riga, Latvia.
Poole
Robert K
RK
Department of Molecular Biology and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
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
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