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Volume 133,
Issue 6,
1987
Volume 133, Issue 6, 1987
- Pathogenicity And Medical Microbiology
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Analysis of Sheath and Core Structures of the Axial Filament of Treponema pallidum
More LessSummary: Electron microscopy and SDS-PAGE have been used to analyse the polypeptide and antigenic composition of the sheath and core components of the axial filament of Treponema pallidum. The sheath contains a major 37 kDa polypeptide which was solubilized by a combination of trypsin and urea treatments with concurrent loss of binding of anti-37 kDa monoclonal antibody. These studies also indicated some antigenic heterogeneity within the axial filament population. Trypsin treatment alone removed a number of antigenic determinants from the axial filament but left others intact, suggesting differences in their location within the sheath structure. A second 31·5 kDa polypeptide may also be associated with the sheath. The axial filament core comprises at least two components, an antigenically dominant 33·5 kDa polypeptide and a second of 34 kDa. The structure of the axial filament in T. pallidum and Treponema phagedenis biotype Reiterii was similar, but antigenic cross-reactivity of sheath and core components was incomplete.
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Inter-strain Homology of Pilin Gene Sequences in Neisseria meningitidis Isolates That Express Markedly Different Antigenic Pilus Types
More LessSummary: Neisseria meningitidis isolates examined in this study elaborated one of two pilus types that were antigenically markedly different. Each pilus type reacted either with SM1, a monoclonal antibody that recognizes an epitope common to all gonococcal pili, or with a polyclonal antiserum raised against meningococcal pili that did not react with SM1, but not both. Total genomic DNA from all N. meningitidis isolates analysed, irrespective of pilus type, contained at least one region with extensive homology to a gonococcal pilE probe. Different N. meningitidis strains possessed one of several configurations of genomic pilE-homologous segments. Chromosomal rearrangement of pilE-homologous sequences was associated with P+ to P− pilus phase transition in the strains examined. The arrangement of pilE-homologous segments in total genomic DNA from N. meningitidis isolated from the blood and cerebro-spinal fluid of the same patient was apparently identical.
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Mannose Inhibition as a Significant Marker for Differentiating among Novobiocin-resistant Staphylococci of Relevance in Clinical Microbiology
More LessSummary: A specific method for the identification of Staphylococcus saprophyticus among novobiocin-resistant species isolated from man is described. The test is based on novobiocin resistance, non-fermentation of d-mannose and early inhibition with late secondary growth on glucose/man-nose + novobiocin agar plates. On this medium novobiocin-resistant Staphylococcus cohnii showed a confluent, continuous and homogeneous growth after 24 h which remained unchanged at 48 h whether or not it fermented d-mannose, whereas novobiocin-resistant Staphylococcus xylosus fermented d-mannose. These results are discussed in relation to a possible causal role of PTS enzymes and phosphomannose isomerase deficiency in mannose inhibition.
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Platelet Aggregation by Group B Streptococci
More LessSummary: Forty-six strains of group B streptococci (GBS), including various serotypes and nonserotypable strains, were tested for their ability to induce platelet aggregation in human plateletrich plasma; four strains, all belonging to type III, showed a positive reaction. The characteristics of the reaction were investigated in these four positive strains. Aggregation was dependent on the ratio of bacteria to platelets, being maximal at a ratio of 4·3. Platelet aggregation was inhibited by EDTA (100% inhibition at 3·1 mM), indomethacin (100% inhibition at 10 mM), acetylsalicylic acid (93-100% inhibition at 5·0 mM) and quinacrine (100% inhibition at 0·25 mM). Thus the reaction was cation-dependent and required cyclooxygenase activity. Assays for cytosolic lactate dehydrogenase did not indicate platelet lysis. GBS induced the release of [3H]serotonin, which was maximal (68-78%) at 10 min after the reaction was started. Experiments with gel-filtered platelets suggested that GBS-induced platelet aggregation required both fibrinogen and heat-resistant (56°C, 30 min) serum factors. Type-specific antisera prevented the platelet aggregation activity of heat-killed bacteria, but not of live bacteria. Trypsin digestion of the bacterial cells caused an almost complete loss of the platelet aggregation activity.
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- Physiology And Growth
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Environmental Regulation of Methanol and Formaldehyde Metabolism by Methylophilus methylotrophus
More LessSummary: Methylophilus methylotrophus was grown in continuous culture at different dilution rates under either methanol or oxygen limitation. Methanol dehydrogenase and formate oxidation were repressed by the presence of high concentrations of methanol in the growth medium, whereas hexulose phosphate synthase was constitutive and the glucose-6-phosphate and 6-phospho-gluconate dehydrogenases were regulated only by the growth rate. Chemical analysis and 13C NMR spectroscopy showed that the oxidation of methanol was accompanied by the spillage of 0 to 50% of the input carbon as formaldehyde and dihydroxyacetone, the extent of which reflected the methanol dehydrogenase: hexulose phosphate synthase activity ratio and/or the energy status of the cells. It is concluded that the observed regulation of key enzymes of methanol and formaldehyde metabolism by the growth environment occurs in order to achieve the required in situ rates of energy conservation and carbon flux demanded by the imposed growth rate, and that the spillage of formaldehyde and dihydroxyacetone reflects limitations on metabolism imposed by kinetic and/or metabolite pool effects.
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The Effect of Catalase on Recovery of Heat-injured DNA-repair Mutants of Escherichia coli
More LessSummary: The apparent sensitivity of Escherichia coli K12 to mild heat was increased by recA (def), recB and polA, but not by uvrA, uvrB or recF mutations. However, addition of catalase to the rich plating medium used to assess viability restored counts of heat-injured recA, recB and polA strains to wild-type levels. E. coli p3478 polA was sensitized by heat to a concentration of hydrogen peroxide similar to that measured in autoclaved recovery medium. The apparent heat sensitivity of DNA-repair mutants is thus due to heat-induced sensitivity to the low levels of peroxide present in rich recovery media. It is proposed that DNA damage in heated cells could occur indirectly by an oxidative mechanism. The increased peroxide sensitivity of heat-injured cells was not due to a decrease in total catalase activity but may be related specifically to inactivation of the inducible catalase/peroxidase (HPI).
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A Mutant of Streptococcus pneumoniae That Exhibits Thermosensitive Penicillin Tolerance and the Paradoxical Effect
More LessSummary: Mutants of Streptococcus pneumoniae that contain active autolysin and yet cannot be induced to lyse during treatment with penicillin (Lyt+Tol+ mutants) have been described. We have now shown that these mutants are temperature dependent (32 °C); at 37 °C these bacteria underwent penicillin-induced lysis. In addition, mutants at the lysis-permissive temperature showed the so-called ‘paradoxical response’ to penicillin. Temperature shift experiments indicated that the change from tolerant to lytic response or vice versa is a fast process. No differences were detected in autolysin specific activity or in the kinetics of inhibition of protein, peptidoglycan and teichoic acid syntheses in cells treated with penicillin at 32 and 37 °C. The results of genetic crosses indicated that the thermosensitivity of penicillin-induced autolysis in the Lyt+Tol+ mutants is not a property of the autolytic enzyme itself. The observations suggest that the thermosensitive process in the mutants represents either a step(s) in autolysin regulation or involves some difference in the structure of the cell walls produced at 32 °C versus 37 °C.
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Long-term Studies of Ciliate-Bacterial Interactions: Use of a Chemostat Fed with Bacteria Grown in a Separate Chemostat
More LessSummary: Two-stage chemostat cascades have been used to study growth of the ciliate Tetrahymena pyriformis on Escherichia coli over extended periods of time. Upward drifts (continuous, slow, uni-directional changes) of ciliate number density and downward drifts of ciliate mean cell size and density of residual bacteria occurred for many generations of ciliates before steady states were obtained. Ciliate chemostats were operated at two different dilution rates. Rates of drift were slower, and drifts persisted longer, both in terms of time and in terms of numbers of generations, in the chemostats operated at the higher dilution rate. Some speculations on the origins of the drifts are presented.
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- Systematics
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Chromosomal DNA Probes for the Identification of Bacteroides Species
More LessSummary: We compared 22 Bacteroides species by DNA-DNA homology studies using the S1 endonuclease method. None of the currently defined species shared more than 30% DNA homology with any other species examined with the exception of B. buccae and B. capillus (which along with B. pentosaceus are now considered a single species), which shared 86% of their DNA sequences. Two clusters showed weak genetic relationships, with DNA homology > 10%. The first cluster included B. corporis, B. disiens, B. bivius, B. intermedius and B. melaninogenicus. The second cluster included B. fragilis, B. eggerthii, B. ovatus, B. thetaiotaomicron and B. uniformis. Five of the oral species, B. asaccharolyticus, B. gingivalis, B. loescheii, B. intermedius and B. melanogenicus, were chosen for study as whole chromosomal probes in dot blot assays. These were tested against 243 clinical strains biochemically identified as Bacteroides species. The DNA probes correctly identified 94% of the clinical strains. DNA probe and biochemical identification was 100% for two of the five species. In contrast, only 86% of the strains biochemically identified as B. intermedius were identified by the DNA probe. The DNA probes gave a species identification to seven strains which could not be biochemically identified.
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BCG Identification by DNA Restriction Fragment Patterns
More LessSummary: Seven daughter strains of BCG were characterized by restriction fragment analysis with the enzymes BstEII, PvuII and BclI. Comparisons of fragment patterns confirmed that BCG is correctly classified as a Mycobacterium bovis variant and suggested that the Swedish strain is most closely related to the original BCG strain.
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