[Comparative finestructural studies of bacteria with the methods negative-staining, ultrathin sectioning and freeze-etching (author's transl)].
Explore the source record for details and available documents.
Bacteria↗
Biomedical subjects
F Mayer
Publications and source records attributed to F Mayer.
Isolation and partial characterization of normal and defective bacteriophages of gram-negative hydrogen bacteria.
Widespread defective lysogeny was detected in Alcaligenes eutrophus by electron microscopic analysis of cultures. Mitomycin C treatment of the cultures resulted in the production of defective (inco-) particles. Polysheaths were produced both with and without induction. With the simultaneous isolation technique six phages were isolated for hydrogen-oxidizing strains of the new species Pseudomonas pseudoflava. The phages were able to replicate under autotrophic conditions and were found to have a very restricted host range. Electron microscopic analysis allowed classification into two structural groups. Group I contained phages with contractile tails; group II contained phages with flexible, noncontractile tails. All but one (gb) of the new phages were shown to be temperate by isolation of lysogens and induction with mitomycin C.
Alcaligenes↗
Electron microscopic investigation of the hydrogen-oxidizing acetate-forming anaerobic bacterium Acetobacterium woodii.
Acetobacterium woodii is a Gram-positive anaerobic nonsporeforming bacterium able to grow on H2 and CO2 as sole sources of energy. The product of fermentation is acetic acid. Fine structural analysis showed rod-shaped flagellated cells, and coccoid cells without flagella arranged predominantly in pairs and chains. The cell wall was found to be composed of three layers. The cell surface exhibited a periodic array of particles consisting of subunits. The cytoplasmic membrane showed particles either in random distribution or in a hexagonal pattern. Intracytoplasmic membranes were rarely observed, whereas inclusion bodies of varying shapes, predominantly in an uncommon disc-shape, could frequently be observed. Their content was dissolved in ultrathin sections indicating hydrophobic nature.
Acetates↗
Complexes of Escherichia coli lac-repressor with non-operator DNA revealed by electron microscopy: two repressor molecules can share the same segment of DNA.
Explore the source record for details and available documents.
Binding Sites↗
Micromorphology of Gram-negative hydrogen bacteria. I. Cell morphology and flagellation.
The cell morphology, the arrangement and fine structure of flagella and the piliation of the following Gram-negative aerobic hydrogen bacteria have been studied: Alcaligenes eutrophus, Alcaligenes paradoxus, Alcaligenes ruhlandii, Pseudomonas flava, Pseudomonas pseudoflava, Pseudomonas palleronii, Pseudomonas facilis, Aquaspirillum autotrophicum, Paracoccus denitrificans, Corynebacterium autotrophicum, and strains MA 2 and SA 35. The identity of the bacteria was examined by their substrate spectra and type of flagellation. Three types of flagellar fine structure were differentiated. The presence of pili was noted in strains of Alcaligenes paradoxus, Pseudomonas flava, P.pseudoflava, P.palleronii, and P.facilis.
Alcaligenes↗
Micromorphology of Gram-negative hydrogen bacteria. II. Cell envelope, membranes, and cytoplasmic inclusions.
The fine structure of the cell envelope, of membrane systems and of cytoplasmic inclusions of Gram-negative aerobic hydrogen bacteria has been studied. The results have been tabulated, and three main groups could be recognized: Group 1: Alcaligenes eutrophus, A.paradoxus, A.ruhlandii, Pseudomonas facilis, P.flava, P.pseudoflava, P.palleronii, and Aquaspirillum autotrophicum; Group 2: "Corynebacterium" autotrophicum and strains MA 2 and SA 35; Group 3: Paracoccus denitrificans. Special structures related to the chemoautotrophic way of life of the hydrogen bacteria were not observed.
Alcaligenes↗
[Experimental repair of tendons with cutis grafts. Light and polarization microscopic study (author's transl)].
Autologous and homologous cutis grafts have been used for the repair of experimental defect of the tendon of the m. ext. carpi ulnaris in adult dogs. Newly formed tendon tissue was found on the frame of the cutis graft about 8 weeks after the implantation. The structure of the newly formed tendon was investigated by light and polarization microscopy up to 8 weeks postoperatively.
Animals↗
Purification, some properties and quaternary structure of the D-ribulose 1,5-diphosphate carboxylase of Alcaligenes eutrophus.
D-Ribulose 1,5-diphosphate carboxylase has been purified from autotrophically grown cells of the facultative chemolithotrophic hydrogen bacterium Alcaligenes eutrophus. The enzyme was homogeneous by the criteria of polyacrylamide gel electrophoresis. The molecular weight of the enzyme was 505000 determined by gel filtration and sucrose density gradient centrifugation, and a sedimentation coefficient of 18.2 S was obtained. It was demonstrated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis that the enzyme consists of two types of subunits of molecular weight 52000 and 13000. Electron microscopy on the intact and the partially dissociated enzyme lead to the construction of a model for the quaternary structure of the enzyme which is composed of 8 large and 8 small subunits. The most probable symmetry of the enzyme molecule is 4:2:2. Michaelis constant (Km) values for ribulose 1,5-diphosphate, Mg2+, and CO2 were 0.59 mM, 0.33 mM, and 0.066 mM measured under air. Oxygen was a competitive inhibitor with respect to CO2 suggesting that the enzyme also exhibits an oxygenase activity. The oxygenolytic cleavage of ribulose 1,5-diphosphate was shown and a 1:1 stoichiometry between oxygen consumption and 3-phosphoglycerate formation observed.
Alcaligenes↗
Identification and physiological characterization of the nitrogen fixing bacterium Corynebacterium autotrophicum GZ 29.
The coryneform hydrogen bacterium strain GZ 29, assigned to Corynebacterium autotrophicum fixed molecular nitrogen under autotrophic (H2, CO2) as well as under heterotrophic (sucrose) conditions. Physiological parameters of nitrogen fixation were measured under heterotrophic conditions. The optimal dissolved oxygen concentration for cells grown in a fermenter with N2 was rather low (0.14 mg O2/l) compared with cells grown in the presence of NH+4 (4.45 mg O2/l). C. autotrophicum GZ 29 had a doubling time of 3.7 h at 30 degrees C with N2 as N-source and sucrose as carbon source and at optimal pO2. Acetylene reduction reached values of 12 nmoles of ethylene produced/min X mg protein. Although the oxygen concentration in the growing culture was kept constant, the optimal dissolved oxygen tension for the acetylene reduction assay shifted to higher pO2-values. The overall efficiency of nitrogen fixation amounted to 22 mg N fixed/g sucrose consumed; it reached a maximal value of 65 mg N fixed/g sucrose consumed at the beginning of the exponential growth phase. Intact cells reduced acetylene even under anaerobic test conditions; further anaerobic metabolic activity could not be ascertained so far.
Acetylene↗
Determination of molecular weight and molecular structure of rat-liver pyruvate carboxylase.
The molecular weight of pyruvate carboxylase isolated from pigeon and rat liver mitochondria was examined using analytical ultracentrifugation and electron microscopy. The enzyme molecule appeared as a tetramer with the four subunits arranged at the corners of a square. Sedimentation studies in the analytical ultracentrifuge, extrapolated to infinite dilution, showed the tetramer to have a molecular weight Mc=0r of 280 000 and an So20,w of 12.7 S. The tetramer could be dissociated into trimers and dimers of lower specific enzymic activity by storage at 4 degrees C or incubation at -- 20 degrees C at low protein concentrations. The isolated trimers and dimers had a molecular weight Mc=0r of 210 000 and 140 000, respectively, and an So20,w of 10.85 S and 7.55 S, respectively. Incubation with 2 M urea at 20 degrees C yielded enzymically inactive subunits (Mc=0r = 70 000; So20,w = 4.95 S). The molecular weights (for pyruvate carboxylase and its subunits), as calculated from the subunit diameter observed in the electron microscope, were consistent with the values obtained from sedimentation studies.
Animals↗
Structure of plain and complex flagellar hooks of Pseudomonas rhodos.
The proximal hooks of plain and complex flagella produced by a strain of Pseudomonas rhodos have been analyzed by electron microscopy and optical diffraction and filtering. Plain flagellar hooks are cone-shaped, 70 nm long, and 13 to 21.5 nm wide, and consist of helically arranged subunits. Complex flagellar hooks are cylinders, 180 to 190 nm long, and 15 to 16 nm wide, and are composed of globular subunits. The structure comprises four small-scale helical rows of subunits intersecting bewteen 10 and 11 large-scale helices of pitch angle 80 degrees. The axial and lateral dimensions of the unit cell, which define the surface lattice, are 4.9 and 4.7 nm, respectively. In addition, a core structure, approximately 5 nm wide, has been demonstrated inside the hook cylinder. Complex flagellar hooks were isolated and purified by gradient centrifugation after acid degradation of the attached filaments. Isolated hook particles have an average sedimentation constant of 130S and consist of a protein of molecular weight 43,000. A model of the complex flagellar hook is presented, and its possible role in flagellar assembly and rotation is discussed.
Flagella↗
Purification and characterization of N-acetylneuraminate lyase from Clostridium perfringens.
Clostridium perfringens cells were cultivated on a large scale using an automatic system. 2) N-Acetylneuraminate lyase, which is a cytosolic enzyme, was liberated from the bacteria by cell lysis using lysozyme in hypotonic solution. The enzyme was purified 770-fold by precepitation with ammonium sulfate, filtration on Sephadex A-50 and final preparative electrophoresis in a 7.5% polyacrylamide gel. Yield: 12 mg from 1 kg wet cell paste; specific activity: 167 nkat/mg protein. 3) The enzyme preparation appeared homogeneous in analytical disc electrophoresis, in gel electrophroesis in 0.1% sodium dodecylsulfate or 8m urea and in immunoelectrophoresis. Contaminating enzyme activities were not detected. 4) The isoelectric point of pH 4.7 was found for the enzyme. At 278 nm a molar extinction coefficient of 6.4 x 10(4)M-1 Xcm-1 was determined. The enzyme exhibited a Km value for N-acetylneuraminic acid of 2.8mM at its pH optimum of pH 7.2. The pH dependence of the Km value gives evidence that an ionizing guoup in the active center of the enzyme with a pKe value of 6.4 may be involved in the catalytic reaction. Pyruvate inhibited the cleavage reaction of N-acetylneuraminic acid competitively; Ki = 2.9mM. 5) An average molecular weight of 99200 was determined for the native enzyme using different methods. After denaturation in sokium dodecylsulfate or urea, a mean molecular weight of only 50000 could be demonstrated, indicating the existence of two enzyme subunits. The lyase molecule was shown by electron microscopy, using a negative staining technique, to consist of two hemispherical parts. 6) Two active sites per native enzyme molecule, probably corresponding to one active site per subunit, were found by incubation of the enzyme with radioactive pyruvate followed by borohydride reduction. The results obtained from chemical modification of the lyase with 5-diazonium-1H-tetrazole and iodocaetamide under various conditionsare interpreted as evidence for the presence of two reactive histidine residues in the enzyme molecule. It is probable that one residue per subunit forms the nucleophilic group participating in enzyme catalysis. A model suggesting the mechanism of reversible cleavage of N-acylneuraminic acids by the lyase is presented.
Binding Sites↗
[Complications of mediastinoscopy].
Explore the source record for details and available documents.
Adult↗
[Resection of the liver using Ton That Tung's method].
Explore the source record for details and available documents.
Echinococcosis, Hepatic↗
[Electron microscopy of ageing cells of Pseudomonas rhodos: fine structure of native and isolated tubular membranes (author's transl)].
During a 10 day-incubation on agar surfaces at 30 degrees C, cells of the gram-negative soil bacterium Pseudomonas rhodos pass through three phases distinguishable by physiological and morphological criteria. When viewed by electron microscopy, typically "rolled" mesosomes could frequently be observed in young cells. In aged cells instead, loosely rolled or stretched-out, flattened tubules could be discerned, presumed to be degenerate mesosomes. Tubular flattened structures have been isolated from these cells by lysozyme treatment or sonication and were concentrated by differential centrifugation. Electron micrographs of these preparations showed long, straight tubules which sometimes appeared sealed at one end. Their width was 34 +/- 5 nm. They contained a lining of material, which could be digested by trypsin leaving behind an electron-transparent matrix. In rare cases, isolated tubules showed a periodic fine structure composed of ellipsoidal subunits. Optical diffraction analysis yielded a lattice consisting of subunits arranged in helices of pitch-angle 27 degrees; the unit cell dimensions were shown to be 112 X 56 A. Owing to their sensitivity to trypsin, components of the regular lattice are supposed to consist of protein. It is postulated that these protein components are layered onto a tubular membrane. These tubules are clearly distinguishable by their shape and fine structure from the periodic structure of a P. rhodos cell wall layer, which exhibits a tetragonal pattern, and also from polyheads and polysheaths of defective bacteriophages. Their possible origin from intact mesosomes in discussed.
Aging↗
Denaturation map of the circular mitochondrial genome of Neurospora crassa.
A denaturation map of mitochondrial DNA from the wild type strain 5256 of Neurospora crassa was constructed by computer analysis of the contour length distribution of single- and double-stranded regions of nineteen circular and three full length linear molecules after partial denaturation. The data suggest that mitochondrial DNA in this strain is a homogeneous population of a circular molecule of molecular weight 41 - 10(6) with an asymmetric distribution of AT-rich regions, and that linear molecules derive from this genome by random breaks during isolation.
Computers↗
Electron microscopic characterization of Rhizobium bacteriophage 16-6-12 and its isolated deoxyribonucleic acid.
Bacteriophage 16-6-12 of Rhizobium lupini has a long, non-contractile tail and a head which is hexagonal in outline. The tail is 140 nm in length, 11 nm in diameter, and carries a short term fiber. Analysis of the tail structure by optical diffraction indicates that it is of the helical "stacked disc" type. After phenol-extraction from purified particles, the DNA of phage 16-6-12 can circularize in vitro. No significant difference in contour length was observed between the linear (14.34 plus or minus 0.28 mum) and circular (14.44 plus or minus 0.24 mum) forms of molecules. After partial denaturation with alkali an AT-GC-map was constructed, which shows an asymmetric distribution of AT- and GC-rich regions. It is concluded that this phage DNA can circularize due to the presence of cohesive ends and that it is not circularly permuted.
Bacteriophages↗
Electron microscopy of simian virus 40 DNA configuration under denaturation conditions.
After isolation, the DNA of simian virus 40 appeared as a negative supertwist (form I) or as an open circle with at least one single-strand scission (form II). Under the denaturation conditions usually applied, such as heating in the presence of formaldehyde or application of alkali, form I molecules could appear as "relaxed" circles without single-strand scissions (form I') containing denatured sites not visible under the electron microscope. Form II molecules, under these denaturation conditions, showed partial or complete strand separations allowing the construction of denaturation maps. By using a modified denaturation procedure, i.e., heating of isolated SV40 DNA in the presence of dimethyl sulfoxide and formaldehyde followed by keeping the DNA in this denaturation solution at room temperature for periods up to 3 weeks, partially denatured relaxed circles without single-strand scissions were produced (form I'D) in addition to completely denatured form II molecules. The absence of single-strand scissions in form I'D molecules was demonstrated by a second heat treatment, which did not change the configuration of this molecular form. Form I'D molecules, in contrast to form I', contained denatured sites clearly discerible under the electron microscope. This combined application of two subsequent denaturation steps (denaturation by heating followed by denaturation at room temperature and neutral pH) showed that the molecular configuration I'D originated in two steps. The heating procedure produced molecules not distinquishable by electron microscopy from form I. In contrast to form I, these molecules were assumed to possess "preformed" denaturation sites (form I). Further treatment of form I molecules with denaturation solution at room temperature finally transformed them into convalently closed, relaxed, partially denatured circles exhibiting strand separations easily measurable on electron micrographs (form I'D). Denaturation maps of form I'D molecules were constructed by computer and compared with denaturation maps derived from partially denatured form II molecules. From these denaturation maps it can be concluded that the melting of base pairs occurring during the transition of simian virus 40 DNA form I into form I'D also preferentially happened at sites rich in the bases adenosine and thymine.
Computers↗