Regulatory O2 tensions for the synthesis of fermentation products in Escherichia coli and relation to aerobic respiration.
In an oxystat, the synthesis of the fermentation products formate, acetate, ethanol, lactate, and succinate of Escherichia coli was studied as a function of the O2 tension (pO2) in the medium. The pO2 values that gave rise to half-maximal synthesis of the products (pO0. 5) were 0.2-0.4 mbar for ethanol, acetate, and succinate, and 1 mbar for formate. The pO0.5 for the expression of the adhE gene encoding alcohol dehydrogenase was approximately 0.8 mbar. Thus, the pO2 for the onset of fermentation was distinctly lower than that for anaerobic respiration (pO0.5 </= 5 mbar), which was determined earlier. An essential role for quinol oxidase bd in microaerobic growth was demonstrated. A mutant deficient for quinol oxidase bd produced lactate as a fermentation product during growth at microoxic conditions (approximately 10 mbar O2), in contrast to the wild-type or a quinol-oxidase-bo-deficient strain. In the presence of nitrate, the amount of lactate was largely decreased. Therefore, under microoxic conditions, the pO2 appears to be too high for (mixed acid) fermentation to function and too low for aerobic respiration by quinol oxidase bo.
Becker
S
S
Institut für Mikrobiologie und Weinforschung, Universität Mainz, Becherweg 15, 55099 Mainz, Germany.
Vlad
D
D
Schuster
S
S
Pfeiffer
P
P
Unden
G
G
D000085:Acetates / Q000378:metabolism; D000332:Aerobiosis / Q000235:genetics; D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000693:Anaerobiosis; D019677:Artificial Gene Fusion; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism; D019149:Bioreactors; D003090:Coliphages / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation / Q000235:genetics; D005561:Formates / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D007763:Lac Operon; D007773:Lactates / Q000378:metabolism; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D009566:Nitrates / Q000378:metabolism; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D012097:Repressor Proteins; D019802:Succinic Acid / Q000378:metabolism
D000085:Acetates; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D005561:Formates; D007506:Iron-Sulfur Proteins; D007773:Lactates; D009097:Multienzyme Complexes; D009566:Nitrates; D012097:Repressor Proteins; C041610:arcA protein, E coli; C030544:formic acid; D000431:Ethanol; D019802:Succinic Acid; D010088:Oxidoreductases; C020094:duroquinol oxidase; D000426:Alcohol Dehydrogenase; C068383:adhE protein, E coli; D000445:Aldehyde Oxidoreductases; D010100:Oxygen