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Query: UMLS:C0519030 (Klebsiella)
 21,988 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method for the isolation of an iron-molybdenum cofactor (FeMoCo) from component I of nitrogenase is described. This method is used to isolate FeMoCo from aerobic, anaerobic, facultative, and photosynthetic nitrogen-fixing organisms. The Fe/Mo ratio in the FeMoCo from Azotobacter vinelandii and Clostridium pasteurianum is 8:1. The FeMoCo contains six atoms of acid-labile sulfide per eight Fe atoms. Crystalline component I from A. vinelandii contains 2 Mo, 33 Fe, and 27 acid-labile sulfide atoms per molecular weight of 250,000. The specific activity of FeMoCo is 425 nmol of C(2)H(4) formed/min per nmol of Mo. There is better than 98% reconstitution between FeMoCo and inactive component I in A. vinelandii mutant strain UW45. The FeMoCo yield from component I is about 90%. FeMoCo from nitrogenase component I of C. pasteurianum, Klebsiella pneumoniae, Bacillus polymyxa, and Rhodospirillum rubrum activates inactive component I in an extract from mutant strain UW45 and follows saturation kinetics. The FeMoCo in various nitrogen-fixing organisms seems to be very similar. Wild-type A. vinelandii derepressed for nitrogenase synthesis in tungsten-containing medium and K. pneumoniae mutant strain UN109 are also activated in vitro by FeMoCo. The FeMoCo is very sensitive to oxygen, but is stable even at room temperature as long as it is kept anaerobic and in N-methylformamide, the solvent used for its isolation. FeMoCo is unstable in an aqueous environment, even though it is kept strictly anaerobic. Knowledge of the structure of this cofactor should be useful for understanding the role of molybdenum at the active site of nitrogenase, role of ligands close to molybdenum in electron and proton transfer, and the catalytic mechanism of nitrogen fixation. The FeMoCo might be used as a model for synthesizing catalysts for chemical nitrogen fixation.
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PMID:Isolation of an iron-molybdenum cofactor from nitrogenase. 41 19

At dissolved oxygen tensions of 15 mmHg (2 kPa) and below, nitrate-limited continuous cultures of Klebsiella K312 synthesized nitrate reductase (NR) and nitrite reductase (NiR) and excreted ammonia. Under anaerobic conditions over 60% of the nitrate-nitrogen utilized was excreted as ammonia. In contrast, carbon-limited cultures excreted nitrite at dissolved oxygen tensions of 15 mmHg or below and synthesized NR but not NiR. Ammonia repressed neither NR nor NiR synthesis. These observations indicate that below a critical oxygen tension of 15 mmHg Klebsiella K312 utilizes oxygen and nitrate as electron acceptors. This oxygen tension correlates well with the critical oxygen tension observed for a change from oxidative to fermentative metabolism in cultures of Klebsiella aerogenes. The product of dissimilatory nitrate reduction is ammonia in nitrate-limited cultures but principally nitrite in carbon-limited (nitrate excess) cultures.
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PMID:Influence of oxygen tension on nitrate reduction by a Klebsiella sp. growing in chemostat culture. 47 38

Klebsiella aerogenes NCTC 418 was grown in chemostat cultures (D = 0.17 hr-1; pH 6.8;35 degrees C) that were, successively, carbon-, sulphate-, ammonia-, and phosphate-limited, and which contained as the sole carbon-substrate first glucose, then glycerol, mannitol and lactate. Quantitative analyses of carbon-substrate used and products formed allowed carbon balances to be constructed and direct comparisons to be made of the efficiency of substrate utilzation. With all sixteen cultures, carbon recoveries of better than 90% were obtained. Optimum utilization of the carbon substrate was invariably found with the carbon-limited cultures, the sole products being organisms and carbon dioxide. But the extent to which excess substrate was over-utilized varied markedly with both the nature of the growth-limitation and the identity of the carbon-substrate. In general, sulphate-, ammonia-, and phosphate-limited cultures utilized glycerol more efficiently than mannitol, mannitol better than lactate, and glucose least efficiently. Glucose-containing cultures also synthesized some extracellular polysaccharide. When the carbon source was in excess, a range of acidic compounds generally were excreted. Sulphate-limited cultures, growing on glucose, excreted much pyruvate and acetate, whereas similarly-limited cultures growing on glycerol, mannitol or lactate produced only acetate. Ammonia-limited cultures invariably excreted 2-oxoglutarate and acetate, whereas phosphate-limited cultures produced gluconic acid, 2-ketogluconic acid and acetate, when growing on glucose, but only acetate when growing on mannitol or lactate. From the rates of substrate and oxygen consumption, and the rates of cell synthesis, yield values for both substrate and oxygen were calculated. These showed different trends, but were similar in being highest under carbon-limitation and substantially lower under all other limitations. The physiological significance of these findings, and the probable nature of the regulatory mechanisms underlying "overflow metabolism" are discussed.
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PMID:The regulation of carbohydrate metabolism in Klebsiella aerogenes NCTC 418 organisms, growing in chemostat culture. 76 18

Oxygen-limited (N2-fixing) chemostat cultures of Klebsiella pneumoniae supplied with a N-free medium were established by introducing low atmospheric O2 concentrations into the gas supply of anaerobic glucose-limited N2-fixing chemostat cultures; the molar growth yield for glucose and the efficiency of N2 fixation (mug N fixed/mg glucose consumed) were increased (by up to 82%) from the anaerobic values. Acetylene-reducing activity was inhibited reversibly by O2 in samples from O2-limited and anaerobic glucose-limited chemostat cultures. Oxygen uptake rates in samples from these chemostat cultures were similar, but C2-H2-reducing activity in samples from O2-limited chemostat cultures was more tolerant of low atmospheric O2 concentrations, in part because of a higher population density. In the absence of glucose, O2 was required at a low atmospheric concentration for C2H2 reduction in samples from either O2-limited or anaerobic glucose-limited chemostat cultures. The possibility is discussed that ATP generated from oxidative phosphorylation can be used for N2 fixation in K. pneumoniae.
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PMID:Influence of atmospheric oxygen concentration on acetylene reduction and efficiency of nitrogen fixation in intact Klebsiella pneumoniae. 77 26

The effect was studied of oxygen supply on the changes in total and specific rate of oxygen consumption by the cells, oxygen transfer rate, saturation concentrations of dissolved oxygen and the yields of batch and continuous cultivations. Experiments were done on the microorganism Klebsiella aerogenes CCM 2318 growing on synthetic glucose medium. Continuous cultivations were carried out at dilution rates of 0.96 and 0.178 h-1. The rate of oxygen transfer was determined by the sulphite method and the coefficient KLa was assessed using the dynamic method with a correction for changes in the saturations of dissolved oxygen. A lowered oxygen supply in batch cultivations caused deformations in the course of cell respiration. Comparison of results of batch and continuous cultivations showed that the highest yields Y X/S and Y X/O are attained at low dilution rates without oxygen limitation. Batch cultivations, on the other hand, exhibit the lowest yields and the highest cell respiration levels. In both types of cultivations, a respiration peak was ascertained under the conditions of growth limitation by oxygen.
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PMID:Oxygen transfer rate, respiration and yields in batch and chemostat cultures of Klebsiella aerogenes. 79 73

Events underlying depression of the nitrogen fixation (nif) genes in Klebsiella pneumoniae M5A1 were analyzed in vivo by comparing the effects of selective inhibitors of transcription and translation on subsequent nitrogenase activity (rate of acetylene reduction). When batch cultures were induced for depression, an 87-min lag separated ammonium ion/oxygen removal and the appearance of activity.
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PMID:Arrangement and regulation of the nitrogen fixation genes in Klebsiella pneumoniae studied by depression kinetics. 81 85

Massive pulmonary hemorrhage is a complication which frequently leads to death in newborns with conditions susceptible to surgical treatment. Out of 112 postmortem studies, focal hemorrhage was found in 38 (33.9%) and massive in 34 cases (30.3%). In this series, congenital anomalies were found in digestive tract in 70.5% of the patients. Prematurity andlow weight were not important factors as was hypoxia, which was evident in 70.5% of the cases. Manifestations of respiratory insufficiency, shock, rales in lung fields, bleeding in other places different from the lung, blood leaking through upper respiratory ducts, are all clinical features of diagnostic aid. Disturbances in coagulation tests were detected, the same as drop in figures of hemoglobin, acidosis, hypoxia and hypercapnia. Gram-negative germs, with a predominance of Klebsiella, were isolated in 33 cultures. The radiographic finding with reticulogranular image was unfrequent. Among other precipitating factors of pulmonary hemorrhage, identification was made of the surgical disease by itself, surgical and anesthetic procedures, of ventilatory assistance and therapy with oxygen at high concentration for long periods of time.
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PMID:[Massive pulmonary hemorrhage in surgical pathology of the newborn infant]. 87 35

A novel beta-lactamase inhibitor has been isolated from Streptomyces clavuligerus ATCC 27064 and given the name clavulanic acid. Conditions for the cultivation of the organism and detection and isolation of clavulanic acid are described. This compound resembles the nucleus of a penicillin but differs in having no acylamino side chain, having oxygen instead of sulfur, and containing a beta-hydroxyethylidine substituent in the oxazolidine ring. Clavulanic acid is a potent inhibitor of many beta-lactamases, including those found in Escherichia coli (plasmid mediated), Klebsiella aerogenes, Proteus mirabilis, and Staphylococcus aureus, the inhibition being of a progressive type. The cephalosporinase type of beta-lactamase found in Pseudomonas aeruginosa and Enterobacter cloacae P99 and the chromosomally mediated beta-lactamase of E. coli are less well inhibited. The minimum inhibitory concentrations of ampicillin and cephaloridine against beta-lactamase-producing, penicillin-resistant strains of S. aureus, K. aerogenes, P. mirabilis, and E. coli have been shown to be considerably reduced by the addition of low concentrations of clavulanic acid.
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PMID:Clavulanic acid: a beta-lactamase-inhiting beta-lactam from Streptomyces clavuligerus. 87 38

When cell-saturating amounts of glucose and phosphate were added to steady state cultures of Klebsiella aerogenes that were, respectively, glucose- and phosphate-limited, the organisms responded immediately with an increased oxygen consumption rate. This suggested that in neither case was glucose transport the rate-limiting process, and also that organisms must possess effective mechanisms for spilling the excess energy initially generated when a growth-limitation is temporarily relieved. Steady state cultures of mannitol- or glucose-limited organisms also seemingly generated energy at a greater rate than was required for cell synthesis since gluconate-limited cultures consumed oxygen at a lower rate, at each corresponding growth rate, than did mannitol- or glucose-limited cultures, and therefore expressed a higher YO value. Thus, mannitol- and glucose-limitations must be essentially carbon (and not energy) limitations. The excess energy generated by glucose metabolism is one component of "maintenance" and could be used at lower growth rates to maintain an increased solute gradient across the cell membrane, imposed by the addition of 2%, w/v, NaCl to the growth environment. The maintenance rates of oxygen consumption of K. aerogenes also could be caused to increase by adding glucose discontinuously (drop-wise) to a glucose-limited chemostat culture, or by exchanging nitrate for ammonia as the sole utilizable nitrogen source. The significance of these findings to an assessment of the physiological factors circumscribing energy-spilling reactions in aerobic cultures of K. aerogenes is discussed.
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PMID:The role of energy-spilling reactions in the growth of Klebsiella aerogenes NCTC 418 in aerobic chemostat culture. 101 53

Alterations in selected aerobic and anaerobic fecal microflora of the mouse were determined during exposure to hyperoxic and normoxic hypo- and hyperbaric environments. Examination of fecal cultures obtained during exposure for 6 weeks to either 60 or 77% oxygen concentration 1 atmosphere absolute revealed little alteration in the aerobic or anaerobic flora. There appeared to be only a retardation in the reduction of the Klebsiella-Enterobacter flora which normally occurs after weaning. During exposure to hypobaric environments (100% O-2, 0.2 atmosphere absolute), significant alterations in concentrations of Escherichia coli, slow lactose fermenters, Klebsiella-Enterobacter, and enterococci were found in some instances. All alterations were toward increased concentrations. Variations in concentrations of different colony types of obligately anaerobic gram-positive (anGPR) and gram-negative (anGNR) rods cultured during the same experiments also occurred. One colony type of anGPR appeared to decrease while a second type increased in numbers. Concentrations of three colony types of anGNR were generally, but not always, increased. During hyperbaric exposure (2.8% O-2, 7.5 atmospheres absolute), increased concentrations of Klebsiella-Enterobacter, E. coli, slow lactose fermenters and enterococci were also noted. Changes in numbers of both colony types of anGPR, when occurring, were in the direction of lower numbers. Alteration in numbers of anGNR were in both directions but were more frequent in the direction of higher numbers. After return to normal air for 4 weeks of either hypo- or hyperbaric exposure, fecal concentrations of all organisms tended to revert toward control values with the exception of the anGPR which remained in lower concentrations after termination of the hyperbaric exposure. These observations indicate that, despite the great variation in the fecal flora among individual mice, it is possible to discover the effects induced by altered gaseous environments.
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PMID:Effect of exposure to hyperoxic, hypobaric, and hyperbaric environments on concentrations of selected and aerobic and anaerobic fecal flora of mice. 109 Feb 55


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