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PubMed1968

Pyruvate metabolism by aminopterin-inhibited Aerobacter aerogenes.

1. The synthesis and utilization of both alanine (by reductive amination, oxidative deamination and transamination) and valine (by transamination only) in Aerobacter aerogenes are unaffected by aminopterin. These amino acids, which accumulate in aminopterin-treated cultures of this organism, are therefore considered to be formed as secondary products from the excess of pyruvate that also accumulates. 2. Oxidative metabolism of pyruvate and the synthesis of acetylmethylcarbinol by A. aerogenes cells are unaltered by growth in the presence of aminopterin. 3. Cells from static and anaerobic cultures that have been treated with the folic acid antagonist in the early exponential phase have a decreased ability to cleave pyruvate to acetate and formate, and to effect the exchange of formate with the carboxyl group of pyruvate. 4. 3-Methyl-2-oxobutanoate, the keto acid precursor of valine, cannot replace pyruvate as substrate in either the phosphoroclastic or the exchange reaction.

Alanine↗
PubMed1968

Pyruvate accumulation in growth-inhibited cultures of Aerobacter aerogenes.

1. Accumulation of pyruvate occurs during the early stages of exponential growth of aerobic, anaerobic and static cultures of a strain of Aerobacter aerogenes. In normal cultures of this organism the content of pyruvate increases until most of the glucose of the medium has been consumed, and then declines rapidly. The presence of unconsumed sugar is not the sole reason for the accumulation of keto acid, since this is unaffected by the addition of extra glucose to either exponentialphase or stationary-phase cultures. 2. In aminopterin-inhibited cultures, the rate of glucose utilization is decreased greatly, and pyruvate continues to accumulate throughout the period of incubation. This prolonged phase of accumulation appears to be a consequence of the growth inhibition, and not to a specific action of aminopterin on the phosphoroclastic breakdown of pyruvate, since it occurs also when growth is restricted by the antibiotics streptomycin, chloramphenicol and neomycin. 3. A possible explanation is suggested for the accumulation of pyruvate in the inhibited cultures.

Aminopterin↗
PubMed1972

Anthranilate synthase-anthranilate 5-phosphoribosyl 1-pyrophosphate phosphoribosyltransferase from Aerobacter aerogenes.

1. Anthranilate synthase and phosphoribosyltransferase from Aerobacter aerogenes purify simultaneously and sediment together on sucrose gradients, showing that they occur as an enzyme aggregate. Both activities of the intact aggregate are subject to inhibition by tryptophan. 2. By using appropriate auxotrophic mutants it was shown that an intact active enzyme aggregate is formed when the components come from separate mutant strains. An intact active aggregate can also be formed when one component is from Escherichia coli and the other from A. aerogenes. 3. Phosphoribosyltransferase of A. aerogenes is active when not in an aggregate with anthranilate synthase, but is not subject to tryptophan inhibition, indicating that the inhibitor site is on the anthranilate synthase component. 4. Anthranilate synthase can be active and sensitive to tryptophan inhibition when complexed with an inactive phosphoribosyltransferase. 5. Kinetic studies on the anthranilate synthase activity show that tryptophan is a competitive inhibitor with respect to chorismate and a non-competitive inhibitor with respect to either glutamine or NH(4) (+) ions. This is consistent with a sequential mechanism of the ordered type in which chorismate is the first reactant.

Binding Sites↗
PubMed1969

Regulatory effects of substrates on a phosphotransferase from Aerobacter aerogenes and modification of its activity by partial proteolysis.

An enzyme isolated from Aerobacter aerogenes acts both as phosphomonoesterase and phosphotransferase with glucose, glucosides, glucosamine, and N-acetyl glucosamine as acceptors. When glucose-6-phosphate is the phosphate donor, these acceptors appear to act as activators of the enzyme, while with p-nitrophenyl phosphate, alpha-glycerophosphate, fructose-1,6-diphosphate, and several other phosphate esters as donors, the same acceptors act as noncompetitive inhibitors. With p-nitrophenyl phosphate as the phosphate donor, no inhibition is observed when glucose is replaced as acceptor by 2-deoxy glucose. The inhibition by glucose and other acceptors is eliminated at low pH or by increasing the temperature of reaction. Partial proteolysis of the enzyme by chymotrypsin produces a modified enzyme (gl-phosphotransferase-Ch) that shows altered relative velocities for the hydrolysis of several substrates as well as altered regulatory effects by acceptors.

Chymotrypsin↗
PubMed1973

Nucleotide sequence divergence in the -chain-structural genes of tryptophan synthetase from Escherichia coli, Salmonella typhimurium, and Aerobacter aerogenes.

Two different estimates were obtained for the extent of nucleotide sequence divergence in the structural genes of the tryptophan synthetase alpha-chains of Escherichia coli, Salmonella typhimurium, and Aerobacter aerogenes. One estimate was based on comparisons of the amino acid sequences of the respective alpha chains. The other was derived from measurements of the thermal stability of RNA-DNA hybrids formed with phage DNA carrying the alpha-chain structural gene of E. coli and labeled messenger RNA from the three bacterial species. Comparison of the two estimates suggests that during the course of evolution synonymous codon changes have accumulated in the alpha-chain-structural genes.

Amino Acid Sequence↗
PubMed1967

Dechlorination of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane by Aerobacter aerogenes. I. Metabolic products.

Whole cells or cell-free extracts of Aerobacter aerogenes catalyze the degradation of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) in vitro to at least seven metabolites: 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE); 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD); 1-chloro-2,2-bis(p-chlorophenyl)ethylene (DDMU); 1-chloro-2,2-bis(p-chlorophenyl)ethane (DDMS); unsym-bis(p-chlorophenyl)ethylene (DDNU); 2,2-bis(p-chlorophenyl)acetate (DDA); and 4,4'-dichlorobenzophenone (DBP). The use of metabolic inhibitors together with pH and temperature studies indicated that discrete enzymes are involved. By use of the technique of sequential analysis, the metabolic pathway was shown to be: DDT --> DDD -->DDMU -->DDMS --> DDNU --> DDA --> DBP, or DDT --> DDE. Dechlorination was marginally enhanced by light-activated flavin mononucleotide.

Cyanides↗
PubMed1968

Comparison of reagent-impregnated paper strips and conventional tests for distinguishing Escherichia from Aerobacter: correlation with colonial morphology.

The means for distinguishing Escherichia from Aerobacter (Enterobacter) differ in laboratories and range from complete dependence on colonial reactions on typical gram-negative media to reliance on one or more of the classical indole, methyl red, Voges-Proskauer, citrate (IMViC) parameters. Three colonial types (one prejudged as Escherichia) of lactose-positive rods were catalogued on each of the most commonly used selective media, MacConkey Agar, Endo Agar, and E M B Agar. Each cultural type was presumptively diagnosed and then compared with the expected outcome of individual IMViC tests. The distribution of preliminary identifications was similar from growth patterns on MacConkey Agar and E M B Agar, but it differed markedly from Endo Agar. When organisms initially diagnosed by cultural methods were compared by single IMViC tests, it was found that for each colonial type one of the biochemical parameters was best suited. Thus, for those types initially considered Escherichia, the methyl red or Voges-Proskauer test results agreed most consistently; for other types, the citrate reaction was most satisfactory. In addition, when newly formulated reagent-impregnated paper strip methods for indole, Voges-Proskauer, and citrate were evaluated and compared to the standard methods, agreement was 97% for indole, 90% for Voges-Proskauer, and 95% for Simmons' citrate.

Bacteriological Techniques↗
PubMed1968

Differentiation of Aerobacter-Klebsiella isolated from sugarcane.

Three hundred and eighty-four isolates were obtained in the completed test portion of the most probable number determinations of coliforms in sugarcane sources. Of these isolates, 88% were of the (- - + +) indole, methyl red, Voges-Proskauer, citrate (IMViC) type and were identified as Aerobacter aerogenes according to the protocol of the American Public Health Association (1). Employing 359 of these cultures, a comparative biochemical, serological, and pathogenicity study was carried out with Klebsiella pneumoniae CDC no. 2211-66 type 9. More than 86% of the organisms tested gave biochemical reactions typical of K. pneumoniae. Of the other isolates, 2% were Enterobacter aerogenes, and the remaining 12% were identified as atypical, nonmotile IMViC types. Comparable agglutination titers were also observed between A. aerogenes and the CDC strain of K. pneumoniae when several randomly selected sugarcane strains were reacted with prepared K. pneumoniae whole cell antiserum. Neither the K. pneumoniae reference organism nor selected sugarcane isolates displayed pathogenicity for mice. On the basis of all the analyses performed, it was suggested that such organisms be classified as K. pneumoniae.

Animals↗
PubMed1971

Factors affecting phosphate uptake by Aerobacter aerogenes in a system relating cell numbers to 32P uptake.

The uptake of phosphate, from media limited in this ion, by resting cells of Aerobacter aerogenes has been investigated and shown to be dependent upon several factors. An incubation medium composed of 10(-2)m K(+), 5 x 10(-3)m Mg(2+), 1 mg of glucose per ml, and 1 muCi of (32)PO(4) (3-) per ml, buffered at pH 6.55 with 0.05 mN-2-hydroxyethyl-piperazine-N'-2-ethanesulfonic acid (HEPES), was found to stimulate optimum accumulation of (32)P-orthophosphate. The temperature of incubation, incubation time, the concentration of unlabeled orthophosphate, as well as arsenate, and several metabolic inhibitors were found to affect the accumulation. The labeled cells were collected on a membrane filter, which had been previously boiled in glass-distilled water, for measurement of the radioactivity accumulated. Under optimum conditions, as few as 20,000 cells were capable of accumulating detectable amounts of (32)P-orthophosphate in 1 hr of incubation.

Arsenic↗
PubMed1969

Control of synthesis of malate dehydrogenase in Aerobacter aerogenes.

An inverse linear relationship was observed between the levels of l-malate dehydrogenase (MDH) and growth rates of Aerobacter aerogenes when grown under aerobic and anaerobic conditions on various substrates which served as the sole carbon and energy sources. Deviations from this linearity were found. MDH levels of cells grown aerobically on oxalacetate, l-malate, d-mannose and d-galactose, and of cells grown anaerobically on l-malate and d-mannose were higher than those expected according to this relationship. Enzyme levels of cells grown aerobically on maltose, d-glucuronate, pyruvate, and possibly melibiose and sucrose were lower than the expected ones. Experiments in which the cells were grown on a mixture of two substrates showed that substrates which gave low levels of MDH repressed the synthesis of this enzyme even in the presence of l-malate or other "high-level substrates." Repressed levels were also observed when the mixture contained l-malate together with "intermediate" or high-level substrates. Identical MDH patterns were obtained by acrylamide gel electrophoresis for all the enzymatic preparations.

Arabinose↗
PubMed1969

Basis for the mutational acquisition of the ability of Aerobacter aerogenes to grow on L-mannose.

Growth of Aerobacter aerogenes PRL-R3 on the unnatural hexose l-mannose as a sole carbon source is dependent upon the selection of a mutant. Growth of the mutant on l-mannose did not require the synthesis of novel enzymes for the degradation of l-mannose, since enzymes of the l-rhamnose degradative pathway could serve this function. However, unlike most other apparent gain mutations that have been described, the mutant was not constitutive for the degradative enzymes; isomerase, kinase, and aldolase activities functional in the degradation of both l-mannose and l-rhamnose were induced by either of these hexoses in the wild type as well as in the mutant. The fact that the wild type could metabolize l-mannose also ruled out the possibility that the cells were not permeable to l-mannose. Growth of the wild type on nutrient broth was severely inhibited by l-mannose coincident with the onset of l-mannose metabolism. A similar inhibition of growth of the mutant was overcome in about 2 hr. Both strains utilized l-rhamnose and l-mannose sequentially in a mineral medium containing both of these hexoses; at the onset of l-mannose metabolism, growth of the wild type, but not of the mutant, was inhibited. Thus, wild-type A. aerogenes cannot grow on l-mannose because of the toxicity of l-mannose or its metabolites. A mutation which overcomes the toxicity enables the organism to utilize l-mannose as a sole source of carbon and energy for growth.

Culture Media↗
PubMed1970

Pathways of anaerobic acetate utilization in Escherichia coli and Aerobacter cloacae.

Acetate-1-(14)C was added to anaerobic glucose-fermenting cultures of Escherichia coli and Aerobacter cloacae. In the E. coli culture, lactate formation occurred late in the fermentation, when the rate of production of formate and acetate had decreased. The occurrence of acetate label in the lactate indicated formation of pyruvate from acetyl-coenzyme A (CoA) and formate. In the A. cloacae cultures, substantial amounts of acetate label were found in the 2,3-butanediol formed. Evidence is presented that the label could have entered the diol only by conversion of formate and acetyl-CoA into pyruvate. The observed levels of radioactivity in the diol indicated that during diol formation the reaction yielding formate and acetyl-CoA from pyruvate CoA was operating close to equilibrium. The shift in metabolism from formation of acetate, ethyl alcohol, and formate to the formation of butanediol or lactate appears to be due basically to an approach to equilibrium of the pyruvate-splitting reaction, whatever the induction mechanism by which the shift is implemented.

Acetates↗
PubMed1970

D-apiose reductase from Aerobacter aerogenes.

A strain of Aerobacter aerogenes PRL-R3 has been isolated which utilizes d-apiose as its sole source of carbon. A new enzyme, d-apiose reductase, was discovered in this strain. The enzyme was not present when the strain was grown on d-glucose. d-Apiose reductase catalyzes the nicotinamide adenine dinucleotide-dependent interconversion of d-apiose and d-apiitol. The enzyme is specific for d-apiose and d-apiitol, with a few possible exceptions. The K(m) for d-apiose is 0.02 m. The K(m) for d-apiitol is 0.01 m. The enzyme is almost completely specific for the reduced and oxidized forms of nicotinamide adenine dinucleotide. When cell-free extracts were centrifuged at 100,000 x g for 1 hr, the enzyme remained in solution. Optimal activity for the reduction of d-apiose was obtained at pH 7.5 in glycylglycine buffer, whereas for the oxidation of d-apiitol it was obtained at pH 10.5 in glycine buffer. Enzymatic reduction of d-apiose was not appreciably affected by the presence of 0.02 m ethylenediaminetetraacetate. Paper chromatography and specific spray reagents were used to identify d-apiitol and d-apiose as the products of this reversible reaction. d-Apiose and d-apiitol did not serve as substrates for ribitol dehydrogenase and d-arabitol dehydrogenase from A. aerogenes PRL-R3.

Alcohol Oxidoreductases↗
PubMed1971

Sorbitol metabolism in Aerobacter aerogenes.

Sorbitol (d-glucitol) metabolism in Aerobacter aerogenes PRL-R3 is shown to proceed via the pathway: sorbitol --> sorbitol 6-phosphate --> d-fructose 6-phosphate. Sorbitol phosphorylation is mediated by a phosphoenolpyruvate (PEP):sorbitol 6-phosphotransferase system, and sorbitol 6-phosphate oxidation by a pyridine-nucleotide-linked dehydrogenase. Mutants deficient in sorbitol 6-phosphate dehydrogenase or a component (enzyme I) of the phosphotransferase system did not grow on sorbitol, whereas revertants which had regained these enzymatic activities grew normally. Extracts of the enzyme I-deficient mutant failed to catalyze the phosphorylation of sorbitol in the presence of PEP, and adenosine 5'-triphosphate could not replace the PEP requirement for sorbitol phosphorylation in extracts of the wild-type strain.

Adenosine Triphosphate↗
PubMed1971

Function of ubiquinone in electron transport from reduced nicotinamide adenine dinucleotide to nitrate and oxygen in Aerobacter aerogenes.

The possible role of quinones in the electron transport system of Aerobacter aerogenes was investigated. The only quinone found in measurable amounts in bacteria grown in minimal media under both aerobic and anaerobic conditions was ubiquinone-8. Membrane-bound ubiquinone-8 could be removed by extraction with pentane, or destroyed by ultraviolet irradiation, with a concomitant loss of both reduced nicotinamide adenine dinucleotide (NADH) oxidase and NADH-linked respiratory nitrate reductase activity. In the extracted membrane preparations, these enzymatic activities could be restored, both to the same degree, by incorporation of ubiquinone-6, -8, or -10, but not by incorporation of menaquinones. The NADH oxidation and the nitrate reduction were sensitive to the respiratory inhibitors dicoumarol, lapachol, and cyanide. The results obtained indicate that ubiquinone-8 mediates the electron transport between NADH and oxygen as well as between NADH and nitrate. Branching of the electron transport chain to oxygen and nitrate occurs after an initial common pathway.

Alkanes↗
PubMed1971

Growth of Aerobacter aerogenes on D-arabinose: origin of the enzyme activities.

Mutants of Aerobacter aerogenes can be selected which are capable of utilizing d-arabinose as a sole source of carbon and energy for growth. Mutants can also be selected which are capable of using l-xylose. The mutational event permitting the utilization of d-arabinose results in the constitutive synthesis of certain enzymes of the l-fucose catabolic pathway. l-Fucose isomerase catalyzes the first reaction in the degradation of d-arabinose: the isomerization of d-arabinose to d-ribulose. No other type of mutation appears to be required to initiate growth on d-arabinose, and wild-type cells induced for the enzymes of the l-fucose catabolic pathway are capable of growth on d-arabinose. The first reaction in the catabolism of l-xylose, the isomerization of l-xylose to l-xylulose, also appears to be catalyzed by constitutively synthesized l-fucose isomerase.

Alcohol Oxidoreductases↗
PubMed1971

Metabolism of D-arabinose by Aerobacter aerogenes: purification of the isomerase.

In Aerobacter aerogenes, the mutational event permitting the utilization of d-arabinose as a source of carbon and energy is a regulatory mutation resulting in the constitutive synthesis of certain enzymes of the l-fucose catabolic pathway. l-Fucose isomerase catalyzes the isomerization of d-arabinose to d-ribulose. This enzyme was purified to homogeneity as indicated by a single band in disc-gel electrophoretic columns and single peaks with column chromatography and ultracentrifugation from the wild-type PRL-R3 strain, induced with l-fucose and two constitutive mutants, 502 and 510. The ratios of the activities of this isomerase on d-arabinose and l-fucose remained constant throughout all purifications. The apparent K(m) of the isomerase from the wild-type strain induced with l-fucose and from the constitutive mutant strains was 5.0 x 10(-2)m for l-fucose and 1.5 x 10(-1)m for d-arabinose. A strain 531 possessing an apparent alteration in the isomerase was isolated from the strain 502. This altered isomerase exhibited a lowered K(m) for d-arabinose.

Ammonium Sulfate↗