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N R Krieg

Publications and source records attributed to N R Krieg.

At least 19 recordsLinked to original sources
PubMed1999

Determining chemotactic responses by two subsurface microaerophiles using a simplified capillary assay method.

A simplified capillary chemotaxis assay utilizing a hypodermic needle, syringe, and disposable pipette tip was developed to measure bacterial tactic responses. The method was applied to two strains of subsurface microaerophilic bacteria. This method was more convenient than the Adler method and required less practice. Isolate VT10 was a strain of Pseudomonas syringae, which was isolated from the shallow subsurface. It was chemotactically attracted toward dextrose, glycerol, and phenol, which could be used as sole carbon sources, and toward maltose, which could not be used. Isolate MR100 was phylogenetically related to Pseudomonas mendocina and was isolated from the deep subsurface. It showed no tactic response to these compounds, although, it could use dextrose, maltose, and glycerol as carbon sources. The chemotaxis results obtained by the new method were verified by using the swarm plate assay technique. The simplified technique may be useful for routine chemotactic testing.

Bacteriological Techniques↗
PubMed1999

Isolation and purification of a Campylobacter upsaliensis autolysin.

Autolytic activity in the soluble and sediment fractions of sonicates of the spiral and the coccoid form of Campylobacter upsaliensis could not be demonstrated by native (nondenaturing) polyacrylamide gel electrophoresis (PAGE). Autolysins were detected, however, by using denaturing sodium dodecyl sulfate (SDS)-PAGE gels containing either purified Escherichia coli peptidoglycan or whole cells of Micrococcus luteus (Micrococcus lysodeikticus) as the turbid substrate, with subsequent renaturation by treatment with Triton X-100 buffer. In renaturing gels that contained Escherichia coli peptidoglycan, 14 putative autolytic bands ranging from 200 to 12 kDa were detected. In similar gels containing whole cells of M. luteus, only a single band appeared with a molecular mass of 34 kDa. This band corresponded to one of the bands present in the gels containing Escherichia coli peptidoglycan. This common autolysin was isolated by adsorbing it from Campylobacter upsaliensis soluble fractions onto M. luteus cells and then subjecting these cells to renaturing SDS-PAGE in gels containing Escherichia coli peptidoglycan. The 34-kDa autolysin differed from a single 51-kDa autolysin unique to the M. luteus cells, and when isolated from an SDS-PAGE gel, was pure when tested by isoelectric focusing. The N-terminal amino acid sequence analysis showed the first 15 amino acids of the 34-kDa autolysin to have 67% identity to a part of antigenic protein PEB4 of Campylobacter jejuni. The purified autolysin was used to immunize rabbits and the antibodies produced precipitated autolytic activity from cell lysates. The specificity of the antibodies was shown by Western blotting: only a single specific band occurred, with a molecular mass of 34 kDa, and thus it seems unlikely that the 34-kDa autolysin was derived from any of the other autolysins that were detected.

Amino Acid Sequence↗
PubMed1998

Identification of a gene for a rubrerythrin/nigerythrin-like protein in Spirillum volutans by using amino acid sequence data from mass spectrometry and NH2-terminal sequencing.

A hydrogen peroxide-resistant mutant of the catalase-negative microaerophile, Spirillum volutans, constitutively expresses a 21.5 kDa protein that is undetectable and non-inducible in the wild-type cells. Part of the gene that encodes the protein was cloned using amino acid sequence data obtained by both mass spectrometry and NH2-terminal sequencing. The deduced 158 amino acid polypeptide shows high relatedness to rubrerythrin and nigerythrin previously described in the anaerobes Clostridium perfringens and Desulfovibrio vulgaris. The protein also shows high similarity to putative rubrerythrin proteins found in the anaerobic archeons Archaeoglobus fulgidus, Methanococcus jannaschii and Methanobacterium thermoautotrophicum. This is the first report of this type of protein in an organism that must respire with oxygen. It seems likely that the novel combination of methodologies used in this study could be applied to the rapid cloning of other genes in bacteria for which no genomic library yet exists.

Amino Acid Sequence↗
PubMed1996

Development of a method based on alkaline gel electrophoresis for estimation of oxidative damage to DNA in Escherichia coli.

A method for estimating DNA strand breakage and subsequent repair based on alkaline gel electrophoresis was developed and tested with isogenic strains of Escherichia coli deficient in DNA repair enzymes. Samples from a cell suspension were removed at 2 min intervals following a 15 min exposure to 20 mmol l-1 H2O2. Catalase was added and the cells were embedded in blocks of low-melting point agarose and lysed. After alkaline gel electrophoresis, photographs of the gels were taken and the relative lengths of the distributions of DNA fragments were measured with a scanner and computer. The lengths were correlated with survival of the cells exposed to H2O2 and with the importance of particular DNA repair enzymes. Alkaline gel electrophoresis appears to be a relatively simple method for analysing the level of H2O2-caused DNA damage and repair in E. coli.

DNA Damage↗
PubMed1994

Oxygen tolerance estimates in Campylobacter species depend on the testing medium.

Oxygen tolerance of the microaerophile Campylobacter jejuni subsp. jejuni varied with different brands of complex media which were used for plating the dilute cell suspensions. The tryptone component was one factor. With some tryptones growth occurred at 21% oxygen whereas with others there was no growth at oxygen levels of 15% or higher. A chemically-defined, agar-solidified plating medium was used to estimate the oxygen tolerance of Camp. jejuni subsp. jejuni, Camp. coli and Camp. fetus subsp. fetus, and also to assess the effect of added scavengers of reactive oxygen intermediates on the oxygen tolerance. Some scavengers such as allopurinol, azelaic acid, caffeine, cimetidine, TEMPOL and pyruvate enhanced oxygen tolerance markedly whereas others such as carnosine, dimethyl thiourea, spermidine and superoxide dismutase had little effect.

Campylobacter↗
PubMed1992

Cytochrome composition and oxygen-dependent respiration-driven proton translocation in Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis.

The membrane fractions of the microaerobically grown type strains of Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis contained membrane-bound cytochrome b, cytochrome c, and CO-binding cytochrome c. Soluble cytochrome c and CO-binding cytochrome c were also present. Although B. gracilis is oxidase negative, it possessed cytochrome c. With H2 or formate as the electron donor, proton efflux from anaerobic cells occurred upon addition of a pulse of oxygen. With formate as the electron donor, the H+/O ratios of W. curva, W. recta, B. ureolyticus, and B. gracilis were 0.75, 1.66, 2.06, and 2.04, respectively. With H2 as the electron donor, the H+/O ratios of W. curva, B. ureolyticus, and B. gracilis were 1.25, 1.97, and 2.36, respectively. Proton translocation was inhibited by the protonophore carbonylcyanide m-chlorophenylhydrazone. The results confirm that the organisms are not anaerobes but are microaerophiles capable of respiring with oxygen.

Bacteroides↗
PubMed1991

Wolinella recta, Wolinella curva, Bacteroides ureolyticus, and Bacteroides gracilis are microaerophiles, not anaerobes.

Although the nonfermentative, asaccharolytic, putative anaerobes Wolinella curva, Wolinella recta, Bacteroides ureolyticus, and Bacteroides gracilis are phylogenetically related to the true campylobacters, the type strains of these species exhibited O2-dependent microaerophilic growth in brucella broth and on brucella agar. The optimum O2 levels for growth of these strains ranged from 4 to 14% in brucella broth and from 2 to 8% on brucella agar, when H2 was provided as the electron donor. No growth occurred under 21% O2, and scant or no growth occurred under anaerobic conditions unless fumarate or nitrate was provided as a terminal electron acceptor. Aspartate, asparagine, and malate also served as apparent electron acceptors. The organisms were catalase negative and, except for B. gracilis, oxidase positive. Catalase added to brucella broth enhanced growth. O2 uptake by all species was inhibited by cyanide and 2-heptyl-4-hydroxyquinoline N-oxide. We concluded that these organisms are not anaerobes but instead are microaerophiles, like their campylobacter relatives.

Anaerobiosis↗
PubMed1990

Catalase activity in Campylobacter jejuni: comparison of a wild-type strain with an aerotolerant variant.

A comparison of Campylobacter jejuni VPI strain H840 (ATCC 29428), which can grow at O2 levels up to 15%, with variant strain MC711-01 (which can grow at O2 levels up to 21-26%) indicated that the specific activity of catalase in crude cell extracts was higher in the variant by a factor of 1.6 to 2.5, depending on cultural conditions. Smaller differences occurred with superoxide dismutase activity, while peroxidase activities were invariably lower in the variant strain. The variant strain was much more resistant than the wild type to the bactericidal effects of H2O2. The results suggest that catalase activity might be one of the factors associated with the greater tolerance of O2 by the variant strain. However, both strains became more susceptible to H2O2 when cultures were initially grown at 6% O2 and then shifted to 21% O2; thus the role of catalase in the oxygen tolerance of C. jejuni is probably minor.

Campylobacter fetus↗
PubMed1988

Bacterial classification: an overview.

Classification of bacteria evolved from limited subjective groupings to general, more objective arrangements based on overall phenotypic similarities. However, classifications based on phenotypic characters lack stability, whereas those based on genetic relatedness tend to be stable. DNA-DNA hybridization has proven to be extremely useful in resolving taxonomic problems at the species level. Broad relationships among bacteria have been identified by comparing ribosomal RNA cistrons; however, many groups based on ribosomal RNA analysis are not easily definable in terms of phenotypic similarities. Unless resolved, these problems could lead to the establishment of two separate classification systems, one phylogenetic and the other practical.

Bacteria↗
PubMed1988

Effect of incubation temperature, ageing, and bisulfite content of unsupplemented Brucella agar on aerotolerance of Campylobacter jejuni.

A mutant strain of Campylobacter jejuni ATCC 29428 was isolated that grows on unsupplemented Brucella agar at O2 levels as high as 21% at 37 degrees C. While measuring the degree of aerotolerance of this mutant on unsupplemented Brucella medium and comparing it with that of the wild type, we found considerable variation among our estimates. As measured by colony counts on unsupplemented Brucella agar incubated at various oxygen levels, the degree of aerotolerance was affected by incubation temperature and the age of the medium. Aerotolerance was consistently higher on plates incubated at 42 degrees C than at 37 degrees C. When the commercial dehydrated Brucella medium that was used to prepare the Brucella agar was stored in a beaker for 2.5 months, the degree of aerotolerance of C. jejuni was decreased. Addition of 0.01% sodium bisulfite reversed this inhibition. Storage of bottles of hydrated Brucella agar for 1.5 months also resulted in a decreased aerotolerance; again, in addition of 0.01% bisulfite reversed the effect. Aerotolerance was greatly decreased when Brucella agar was prepared from all its individual components except 0.01% bisulfite. The results indicate that the bisulfite component of Brucella agar deteriorates during storage of the dehydrated and hydrated media, and that this deterioration can affect measurements of aerotolerance.

Aerobiosis↗
PubMed1985

DNA homology studies of the catalase-negative campylobacters and "Campylobacter fecalis," an emended description of Campylobacter sputorum, and proposal of the neotype strain of Campylobacter sputorum.

Twenty-three strains of catalase-negative campylobacters and five strains of "Campylobacter fecalis," which is catalase-positive, were examined by DNA hybridization experiments. These organisms formed four distinct DNA homology groups corresponding to Campylobacter sputorum, Campylobacter mucosalis, Campylobacter concisus, and a currently unnamed group referred to as the "catalase-negative or weak" (CNW) strains. The strains were further characterized to determine which phenotypic characteristics provide the most reliable identification at the species level. Campylobacter sputorum ssp. sputorum, C. sputorum ssp. bubulus, and "C. fecalis" could not be distinguished by DNA homology; consequently, it is proposed that these three taxa be considered as biovars of C. sputorum. The description of C. sputorum is emended accordingly. ATCC strain 35980 is proposed as the neotype strain of C. sputorum.

Campylobacter↗
PubMed1984

Fructose catabolism in Azospirillum brasilense and Azospirillum lipoferum.

The pathways for catabolism of fructose were investigated in the type strains of Azospirillum lipoferum and Azospirillum brasilense grown aerobically with (NH4)2SO4 as the nitrogen source. When grown on fructose, the former species possessed a complete Entner-Doudoroff pathway, whereas the latter species lacked activity for glucose-6-phosphate dehydrogenase. Both species possessed a complete catabolic Embden-Meyerhof-Parnas pathway. Neither species possessed the key enzyme of the hexose monophosphate pathway, 6-phosphogluconate dehydrogenase. Both species could phosphorylate fructose to fructose-1-phosphate by means of a phosphoenolpyruvate-phosphotransferase system, and high activities of 1-phosphofructokinase occurred. Both species possessed glucokinase activity, but only A. lipoferum had hexokinase activity; moreover, the cells of A. brasilense were nearly impermeable to glucose, accounting for the inability of this species to grow on glucose. Both species possessed pyruvate dehydrogenase, a complete tricarboxylic acid cycle, a glyoxylate shunt, and malic enzyme. Analysis of the acidic end products for both species indicated the formation of only small amounts of various organic acids, and most of the titratable acidity was due to utilization of the ammonium ions of the medium. Gluconic acid was not formed during growth of either species on fructose but was detected during growth of A. lipoferum on glucose; this species also possessed an NADP-linked glucose dehydrogenase and gluconokinase.

Biological Transport, Active↗
PubMed1984

Improved biotyping schemes for Campylobacter jejuni and Campylobacter coli.

Campylobacter jejuni (20 strains) and Campylobacter coli (12 strains) were assigned to four biovars for each species based on phenotypic tests that were easy to perform and interpret. The resulting biotyping schemes offer a greater degree of distinction among C. jejuni and C. coli strains than any of the other biotyping schemes previously described for these organisms.

Alkaline Phosphatase↗
PubMed1984

Differential characteristics of catalase-positive campylobacters correlated with DNA homology groups.

Eighty-four strains of catalase-positive campylobacters could be placed into seven distinct DNA homology groups (species), corresponding to Campylobacter fetus, "C. hyointestinalis," C. jejuni, C. coli, "C. laridis," "C. fecalis," and aerotolerant campylobacters. The biochemical and physiological characteristics of the strains were examined for their correlation with the homology groups. The characterization tests that provided the most reliable differentiation at the species and subspecies level were growth at 25 and 42 degrees C, sensitivity to cephalothin and nalidixic acid, growth in semisolid media containing 1% glycine and 3.5% NaCl, growth on plates containing 1.5% NaCl, growth in a semisolid minimal medium, anaerobic growth in the presence of 0.1% trimethylamine-N-oxide, hydrogen sulfide production in SIM medium and triple-sugar iron agar, hippurate hydrolysis, nitrite reduction, and growth on plates under an air atmosphere.

Aerobiosis↗
PubMed1983

Straight mutants of Spirillum volutans can swim.

Nonhelical mutant cells of Spirillum volutans ATCC 19554 can swim as fast as the helical cells. Consequently, a helical cell shape is not required for motility of this species, and the function of the polar flagellar fascicles is not merely to cause rotation, and therefore translocation, of the corkscrew-shaped cell.

Movement↗
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↗