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N R Krieg

Publications and source records attributed to N R Krieg.

At least 37 records · Page 2Linked to original sources
PubMed1979

Studies of the microaerophilic nature of Campylobacter fetus subsp. jejuni. II. Role of exogenous superoxide anions and hydrogen peroxide.

The addition of bovine superoxide dismutase to Brucella broth or Brucellar agar greatly echanced the oxygen tolerance of Campylobacter fetus subsp. jejuni strain H840 (ATCC 29428). Catalase also enhanced oxygen tolerance, but to a lesser extent. These enzymes must act externally to the bacteria. All of the diverse compounds which enhance oxygen tolerance of C. fetus, including nor-epinephrine and a combination of ferrous sulfate, sodium metabisulfite, and sodium pyruvate, share the ability to quench either superoxide anions or hydrogen peroxide. On the basis of these and other data, we propose that C. fetus is more sensitive to exogenous superoxide anions and hydrogen peroxide than are aerotolerant bacteria, despite the occurrence of superoxide dismutase and catalse activities in C. fetus. Compounds that enhance oxygen tolerance in C. fetus appear to act by quenching superoxide anions and hydrogen peroxide which occur spontaneously in the culture medium.

Campylobacter↗
PubMed1978

Improved media for growth and aerotolerance of Campylobacter fetus.

The microaerophilic nature of Campylobacter fetus has complicated its recovery from human and animal sources. In this study, modifications of brucella agar and broth were tested for enhancement of growth and aerotolerance of 64 strains of C. fetus, representing each subspecies. Brucella agar supplemented with 0.025% each FeSO4 7H2O, sodium metabisulfite, and sodium pyruvate, supported growth of 98, 77, and 63% of the strains at 6% O2, 17% O2, and 21% O2, respectively. Unsupplemented brucella agar supported growth of 94, 48, and 20% of the strains. Brucella broth supplemented with 0.2% FeSO4.7H2O, 0.025% sodium metabisulfite, and 0.05% sodium pyruvate supported growth of 98% of the strains at 21% O2, compared to 75% with unsupplemented brucella broth. With both the supplemented agar and broth, growth responses occurred 1 to 2 days earlier than usual. Growth and aerotolerance of three strains of Campylobacter sputorum subsp. bubulus were not enhanced by the supplements.

Campylobacter↗
PubMed1978

A taxonomic study of the Spirillum lipoferum group, with descriptions of a new genus, Azospirillum gen. nov. and two species, Azospirillum lipoferum (Beijerinck) comb. nov. and Azospirillum brasilense sp. nov.

Sixty-one strains of the root-associated nitrogen fixer Spirillum lipoferum exhibited a similar morphology in peptone--succinate salts medium: vibrioid cells having a diameter of 1.0 micrometer. When grown in broth the cells had a single polar flagellum, but when grown on agar at 30 degrees C lateral flagella of shorter wavelength were also formed. The DNA base composition was 69--71 mol% guanine + cytosine when determined by thermal denaturation. DNA homology experiments indicated the occurrence of two distinct but related homology groups: 46 strains were in group I and 15 strains were in group II. Group II strains were distinguished by their ability to use glucose as a sole carbon source for growth in nitrogen-free medium, by their production of an acidic reaction in a peptone-based glucose medium, by their requirement for biotin, and by their formation of wider, longer, S-shaped or helical cells in semisolid nitrogen-free malate medium. The results indicate that two species exist, and on the basis of their characteristics it is proposed that they be assigned to a new genus, Azospirillum. Strians belonging to group II are named A. lipoferum (Beijerinck) comb. nov., while those belonging to group I are named A. brasilense sp. nov. Strain Sp 59b (ATCC29707) is proposed as the neotype strain for A. lipoferum, and strain Sp 7 (ATCC 29145) is proposed as the type strain for A. brasilense.

Culture Media↗
PubMed1976

Stimulatory effect of dihydroxyphenyl compounds on the aerotolerance of Spirillum volutans and Campylobacter fetus subspecies jejuni.

The aerotolerance of the microaerophilic bacterium Spirillum volutans was greatly stimulated in a defined medium by the presence of dihydroxyphenyl ferric iron-binding compounds such as nor-epinephrine at 10(-5) to 10(-6) M. Dihydroxyphenyl compounds at 2 X 10(-4) M, or iron salts (ferrous or ferric) at high concentration, greatly increased the aerotolerance of a strain of Campylobacter fetus subsp. jejuni when grown on streak plates of Brucella agar. The results suggest that the microaerophilism of these organisms might in part be caused by a failure to synthesize microbial ferric iron-binding compounds at sufficient levels to support aerobic growth.

Aerobiosis↗
PubMed1974

Transport and catabolism of D-fructose by Spirillum itersomii.

Spirillum itersonii ATCC 12639 utilized d-fructose but neither d-glucose nor d-gluconate as a sole source of carbon and energy. The substrate saturation kinetics for d-fructose and d-glucose uptake by whole cells indicated the presence of a carrier-mediated transport system for d-fructose but not for d-glucose. The d-fructose uptake activity was induced (10- to 12-fold increase) during growth on d-fructose-Casamino Acids (CA) or d-glucose-CA medium, but not CA alone. d-Fructose uptake activity was stimulated by Na(+) or Li(+), but was inhibited by KCN, NaN(3), 2,4-dinitrophenol, and p-chloromercuribenzoate. High specific activities of glucokinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydratase, and 2-keto-3-deoxy-6-phosphogluconate aldolase were detected in extracts of cells cultured on d-fructose-CA medium. These enzymatic activities were undetectable in extracts of cells grown in CA or succinate-CA medium. No decrease in the maximally induced specific activities of these enzymes occurred after the addition of succinate to cells during exponential growth on d-fructose-CA. Fructose 1,6-diphosphate aldolase and glucose-6-phosphate isomerase specific activities were approximately the same irrespective of cultural conditions. These results indicated that d-glucose was not utilized by cells of S. itersonii because this bacterium was impermeable to this hexose.

Alcohol Oxidoreductases↗
PubMed1974

Sugar catabolism in Aquaspirillum gracile.

Aquaspirillum (Spirillum) gracile is one of the few spirilla that cause acidification of the medium when cultured with sugars. Acidic reactions have been reported only for d-glucose, d-galactose, and l-arabinose, and the mode of attack of these sugars has not been previously investigated. The soluble portion of extracts of glucose-cultured cells of A. gracile ATCC 19624 was found by spectrophotometric methods to contain enzyme activities characteristic of the Entner-Doudoroff and Embden-Meyerhof-Parnas pathways. No activity for 6-phosphogluconate dehydrogenase (EC 1.1.1.44) was detected. Pyridine nucleotide-linked dehydrogenase activities for l-arabinose and d-galactose (EC 1.1.1.46 and EC 1.1.1.48) occurred in the soluble fraction of cells cultured with either sugar. Glucose-cultured cells contained not only glucokinase (EC 2.7.1.2) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activities but also glucose dehydrogenase (EC 1.1.1.47) activity. Enzymes capable of oxidizing gluconate were not detectable, but gluconokinase (EC 2.7.1.12) activity was present. Paper chromatographic analysis of the spent culture supernatant media from glucose-cultured cells indicated an accumulation of gluconic acid, and this was confirmed by enzymatic methods. Evidence is presented for the production of d-galactonic and l-arabonic acids in cultures containing d-galactose or l-arabinose, respectively.

Alcohol Oxidoreductases↗
PubMed1967

Inhibitio of flagellar coordination in Spirillum volutans.

The motility of Spirillum volutans is caused by the rotation of each polar flagellar fascicle in a direction opposite to that of the more slowly rotating cell. Both flagella form cones of revolution oriented in the same direction. When the cell reverses its motion, both fascicles simultaneously reverse their rotation and also the orientation of their cones of revolution, with the tail fascicle becoming the head and vice versa. Chloral hydrate and phenol were found to cause uncoordination, with both fascicles becoming the head type; MgSO(4), Mg(NO(3))(2), NiSO(4), NiCl(2), CuSO(4), and CuCl(2) also caused uncoordination, with both fascicles becoming the tail type. In all cases, the flagellar fascicles remained highly active but the cells were motionless because of the opposing propulsion; the rotation of the fascicles was in a constant direction without reversal. Uncoordinated states could be maintained for 30 to 60 min. Neutralization of the dual-tail flagellation caused by NiSO(4) could be accomplished with chloral hydrate. At the null point, the flagellar orientation was intermediate between head and tail; the fascicles continually reversed direction of rotation, and, now coordinated, caused the cells to move back and forth. Higher concentrations of chloral hydrate completely overcame the effect of NiSO(4) and caused dual-head flagellation. Optimal concentrations of test compounds were determined with the use of pure cultures and a reproducible growth medium.

Chloral Hydrate↗