0000000000218824
AUTHOR
Dorina Vlad
Significance of pantothenate for glucose fermentation by Oenococcus oeni and for suppression of the erythritol and acetate production.
The heterofermentative lactic acid bacterium Oenococcus oeni requires pantothenic acid for growth. In the presence of sufficient pantothenic acid, glucose was converted by heterolactic fermentation stoichiometrically to lactate, ethanol and CO2. Under pantothenic acid limitation, substantial amounts of erythritol, acetate and glycerol were produced by growing and resting bacteria. Production of erythritol and glycerol was required to compensate for the decreasing ethanol production and to enable the synthesis of acetate. In ribose fermentation, there were no shifts in the fermentation pattern in response to pantothenate supply. In the presence of pantothenate, growing O. oeni contained at l…
Requirement for the Proton-Pumping NADH Dehydrogenase I of Escherichia Coli in Respiration of NADH to Fumarate and Its Bioenergetic Implications
In Escherichia coli the expression of the nuo genes encoding the proton pumping NADH dehydrogenase I is stimulated by the presence of fumarate during anaerobic respiration. The regulatory sites required for the induction by fumarate, nitrate and O2 are located at positions around –309, –277, and downstream of –231 bp, respectively, relative to the transcriptional-start site. The fumarate regulator has to be different from the O2 and nitrate regulators ArcA and NarL. For growth by fumarate respiration, the presence of NADH dehydrogenase I was essential, in contrast to aerobic or nitrate respiration which used preferentially NADH dehydrogenase II. The electron transport from NADH to fumarate …
Regulatory O 2 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 de…
Functional citric acid cycle in an arcA mutant of Escherichia coli during growth with nitrate under anoxic conditions
The operation of the citric acid cycle of Escherichia coli during nitrate respiration (anoxic conditions) was studied by measuring end products and enzyme activities. Excretion of products other than CO2, such as acetate or ethanol, was taken as an indication for a non-functional cycle. From glycerol, approximately 0.3 mol acetate was produced; the residual portion was completely oxidized, indicating the presence of a partially active citric acid cycle. In an arcA mutant devoid of the transcriptional regulator ArcA, glycerol was completely oxidized with nitrate as an electron acceptor, demonstrating derepression and function of the complete pathway. Glucose, on the other hand, was excreted …