The participation of cytochromes in the process of nitrate respiration in klesbsiella (Aerobacter) aerogenes

Oxygen regulation of nitrate uptake in denitrifying Pseudomonas aeruginosa

Oxygen had an immediate and reversible inhibitory effect on nitrate respiration by denitrifying cultures of Pseudomonas aeruginosa. Inhibition of nitrate utilization by oxygen appeared to be at the level of nitrate uptake, since nitrate reduction to nitrite in cell extracts was not affected by oxygen. The degree of oxygen inhibition was dependent on the concentration of oxygen, and increasing nitrate concentrations could not overcome the inhibition. The inhibitory effect of oxygen was maximal at approximately 0.2% oxygen saturation. The inhibition appeared to be specific for nitrate uptake. Nitrite uptake was not affected by these low levels of aeration, and nitrite reduction was only partially inhibited in the presence of oxygen. The regulation of nitrate respiration at the level of transport by oxygen may represent a major mechanism by which the entire denitrification pathway is regulated in P. aeruginosa.

Part of respiratory nitrate reductase of Klebsiella aerogenes is intimately associated with the peptidoglycan

Lysozyme digestion and sonication of sodium dodecyl sulfate (SDS)-purified Klebsiella aerogenes murein sacculi resulted in the quantitative release of both subunits of nitrate reductase, as well as a number of other cytoplasmic membrane polypeptides (5.2%, by weight, of the total membrane proteins). Similar results were obtained after lysozyme digestion of SDS-prepared peptidoglycan fragments, which excluded the phenomenon of simple trapping of the polypeptides by the surrounding peptidoglycan matrix. About 28% of membrane-bound nitrate reductase appears to be tightly associated with the peptidoglycan. Additional evidence for this association was demonstrated by positive immunogold labeling of SDS-murein sacculi and thin sections of plasmolyzed bacteria. Qualitative amino acid analysis of trypsin-treated sacculi, a tryptic product of holo-nitrate reductase, and amino- and carboxypeptidase digests of both nitrate reductase subunits indicated the possible existence of a terminal anchoring peptide containing the following amino acids: (Gly)n, Trp, Ser, Pro, Ile, Leu, Phe, Cys, Tyr, Asp, and Lys.

Nitrate respiration of Klebsiella pneumoniae on amino acids, especially on serine

Anaerobic growth on an amino acids mixture in the presence of nitrate of a strain of K. pneumoniae isolated from soil depended on the presence of serine in the mixture. This organism grew on serine as sole carbon source under anaerobic conditions in the presence of nitrate but not in its absence. Glycylglycine could replace serine. Serine was degraded to acetate, formate, pyruvate, acetone and acetoin with formation of nitrite under these conditions. These products were practically not different from those formed from glucose. Resting cells decomposed serine also in the absence of nitrate forming butanediol and a large amount of formate in place of decreased amounts of acetate and pyruvate. These cells also anaerobically decomposed alanine to products similar to those from serine and phenylalanine to phenylacetate and formate only in the presence of nitrate. Valine was not catabolized under the same conditions. Serine was decomposed to pyruvate and ammonia in the crude extract in the presence and absence of nitrate, indicating participation of serine dehydratase in its breakdown. Phenylalanine appears to be decomposed to phenylpyruvate by transamination coupled to glutamate oxidation and then to phenylacetate and formate. Little growth on serine under anaerobic conditions in the absence of nitrate may be accounted for by the small gain of ATP in the anaerobic breakdown of serine by this organism.

Physiological characteristic and energy balance of Klebsiella aerogenes in a multistage tower fermentor

Biomass growth, consumption of carbon and energy source, specific rates of formation of metabolic byproducts, biomass yield referred to the C-source and to oxygen, respiration rate and the value of RQ were studied in Klebsiella aerogenes CCM 2318 (on a synthetic glucose medium) at different specific growth rates. Maintenance coefficients and the total energy balance of the cultivation process were evaluated for a multistage tower fermentor with a defined interstage mixing. The results pointed to changes in both glucose metabolism and the physiological state of the population, brought about by changes in specific growth rate. As compared with a chemostat, the culture was found to exhibit a different physiological character is stages 1 and 4 despite a considerable interstage mixing.

Energy conservation in chemotrophic anaerobic bacteria

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Oxidation and reduction of membrane-bound cytochrome c in Hemophilus parainfluenzae. Reaction with oxygen, hydrogen peroxide and nitrate

Cytochromes of the a-, b-, c- and d-type become reduced when intact cells of Hemophilus parainfluenzae have become anaerobic following respiration with substrates such as formate or succinate, as shown previously (J. Biol. Chem. (1970) 254, 5096-5100). In the presence of formate after depletion of O2, there is an unusual two-step time course of reduction of the membrane-bound cytochrome c. The proportion of the cytochrome c which is reduced during the second stage is oxidizable by either nitrate or H2O2 and is reduced again when the nitrate or H2O2 have been depleted. We conclude that the observed two-stage reduction of cytochrome c results from the presence of an oxidant, probably H2O2, produced by reaction of formate dehydrogenase with O2. This was shown by the effects of cyanide, catalase and O2. In addition, no evidence for the production of the oxidant is seen when succinate is the substrate oxidized. Although measurements of absorption spectra indicated only one species of cytochrome c, kinetic evidence is presented for some separation of the cytochrome c into more than one electron transport pathway.

Purification, structure and properties of the respiratory nitrate reductase of Klebsiella aerogenes

1. The respiratory nitrate reductase of Klebsiella aerogenes was solubilized from the bacterial membranes by deoxycholate and purified further by means of gel chromatography in the presence of deoxycholate, and anion-exchange chromatography. 2. Dependent on the isolation procedure two different homogeneous forms of the enzyme, having different subunit compositions, can be obtained. These forms are designated nitrate reductase I and nitrate reductase II. Both enzyme preparations are isolated as tetramers having sedimentation constants (s20,w) of 22.1 S and 21.7 S for nitrate reductase I and II, respectively. The nitrate reductase I tetramer has a molecular weight of about 106. 3. In the presence of deoxycholate both enzyme preparations dissociate reversibly into their respective monomeric forms. The monomeric form of nitrate reductase I has a molecular weight of about 260 000 and a sedimentation constant of 9.8 S. For nitrate reductase II these values are 180 000 and 8.5 S, respectively. 4. Nitrate reductase I consists of three different subunits, having molecular weights of 117 000; 57 000 and 52 000, which are present in a 1:1:2 molar ratio, respectively. Nitrate reductase II contains only the subunits with a molecular weight of 117 000 and 57 000 in a equimolar ratio. 5. Treatment at pH 9.5 in the presence of deoxycholate and 0.05 M NaCl or ageing removes the 52 000 Mr subunit from nitrate reductase I. This smallest subunit, in contrast to the other subunits, is a basic protein. 6. The 52 000 Mr subunit has no catalytic function in the intramolecular electron transfer from reduced benzylviologen to nitrate. However, it appears to have a structural function since nitrate reductase II, which lacks this subunit, is much more labile than nitrate reductase I. Inactivation of nitrate reductase II can be prevented by the presence of deoxycholate. 7. The spectrum of the enzyme resembles that of iron-sulfur proteins. No cytochromes or contaminating enzyme activities are present in the purified enzyme. Only reduced benzylviologen was found to be capable of acting as an electron donor. 8. p-Chlormercuribenzoate enhances the enzymatic activity at concentrations of 0.1 mM and lower. At higher p-chlormercuribenzoate concentrations the enzymatic activity is inhibited non-competitively with either nitrate or benzylviologen as a substrate. The inhibition is not counteracted by cysteine.

Role of menaquinone in nitrate respiration in Staphylococcus aureus

Two menaquinone-deficient and one aromatic-deficient mutants of Staphylococcus aureus were unable to reduce nitrate to nitrite. Reinitiation of menaquinone synthesis in the aromatic-deficient mutant by growing it with shikimic acid restored its nitrate respiratory activity. The results clearly demonstrate a role for menaquinone in nitrate respiration in Staphylococcus aureus.