Mutagene Wirkung von Hydrazin auf Escherichia coli-Zellen

1961 ◽  
Vol 48 (13) ◽  
pp. 480-480 ◽  
Author(s):  
Franz Lingens
Keyword(s):  
Escherichia Coli ◽  
Mutagene Wirkung

Inaktivierende und mutagene Wirkung salpetriger Säure auf Zellen von Escherichia coli

1959 ◽  
Vol 14 (8-9) ◽  
pp. 528-537 ◽  
Author(s):  
F. Kaudewitz
Keyword(s):  
Escherichia Coli ◽  
Nitrous Acid ◽  
Single Cells ◽  
Wild Type ◽  
Inactivation Curve ◽  
E Coli ◽  
Auxotrophic Mutants ◽  
Induced Mutants ◽  
Mutagene Wirkung ◽  
Cellular Dna

Cells of E. coli B incubated with NaNO2 undergo inactivation. In non-metabolizing cells the inactivation follows a two hit curve. In metabolizing cells the rate of inactivation is increased and the inactivation curve does not show two-hit kinetics. The rate of inactivation decreases with rising pH and decreasing NaNO2-concentration. Therefore nitrous acid appears to be the active substance.Nitrous acid proved to be a potent mutagen as shown by isolation of auxotrophic mutants. With an inactivation rate of 10-4 about 1.4 per cent of the surviving cells were auxotrophs. The probability that this increase in mutants may be due to selection during inactivation of auxotrophs present before exposure was excluded experimentally. In none of 559 auxotrophic colonies grown from single cells which had survived contact with nitrous acid wild-type sectors were found. For metabolizing and nonmetabolizing cells the increase of the percentage of auxotrophic mutants with increasing time of exposure to HNO2 followed a two-hit curve. In these experiments the percentage of induced mutants was independent of the different rate of inactivation caused by different states of metabolism and dependent only on the time of incubation with nitrous acid. The results are discussed as being in agreement with the assumption that in non-metabolizing cells nitrous acid acts directly on the cellular DNA leading to inactivation and mutation.

Mutagene Wirkung des Zerfalles von radioaktivem Phosphor nach Einbau in Zellen von Escherichia coli

1958 ◽  
Vol 13 (12) ◽  
pp. 793-802 ◽  
Author(s):  
F. Kaudewitz ◽  
W. Vielmetter ◽  
H. Friedrich-Freksa
Keyword(s):  
Escherichia Coli ◽  
Survival Rate ◽  
Positive Selection ◽  
Liquid Nitrogen ◽  
Cellular Structures ◽  
Complete Medium ◽  
E Coli ◽  
Replica Plating ◽  
Mutagene Wirkung ◽  
Inactivation Of Bacteria

Cells of E. coli B/r labelled with 32P undergo inactivation during storage in liquid nitrogen (-196° C). Thawing the samples after storage and plating them immediately on complete medium yields colonies of uniform appearance. However, replica plating them on minimalmedium demonstrates, that during 32P decay there occured a significant increase in nutritionally deficient (auxotrophic) mutants. When 10-4 is the survival-rate, 0.67% of surviving cells give rise to auxotrophic colonies, 40 - 50% of which have prototrophic sectors. During storage the increase of mutants is linear with respect to inactivation of bacteria and to the fraction of 32P decayed. The experiments carried out show, that inactivation and mutation are due to the decay of 32P atoms incorporated in cellular structures and not do effects of freezing, toxicity of contaminants present in the 32P solution, or ionization of β-electrons. An increase of mutants by positive selection in the course of inactivation was excluded experimentally

Structural organization of escherichia coli ribosomes as determined by immuno electron microscopy

1978 ◽  
Vol 36 (2) ◽  
pp. 166-167 ◽  
Author(s):  
G. Stöffler ◽  
R.W. Bald ◽  
J. Dieckhoff ◽  
H. Eckhard ◽  
R. Lührmann ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Ribosomal Proteins ◽  
Structural Organization ◽  
Three Dimensional ◽  
Ribosomal Subunit ◽  
Spatial Arrangement ◽  
Small Subunit ◽  
Antibody Binding ◽  
Immuno Electron Microscopy

A central step towards an understanding of the structure and function of the Escherichia coli ribosome, a large multicomponent assembly, is the elucidation of the spatial arrangement of its 54 proteins and its three rRNA molecules. The structural organization of ribosomal components has been investigated by a number of experimental approaches. Specific antibodies directed against each of the 54 ribosomal proteins of Escherichia coli have been performed to examine antibody-subunit complexes by electron microscopy. The position of the bound antibody, specific for a particular protein, can be determined; it indicates the location of the corresponding protein on the ribosomal surface.The three-dimensional distribution of each of the 21 small subunit proteins on the ribosomal surface has been determined by immuno electron microscopy: the 21 proteins have been found exposed with altogether 43 antibody binding sites. Each one of 12 proteins showed antibody binding at remote positions on the subunit surface, indicating highly extended conformations of the proteins concerned within the 30S ribosomal subunit; the remaining proteins are, however, not necessarily globular in shape (Fig. 1).

Sites of Adsorption of the Bacteriophages T3 and T5 on the Wall of Escherichia Coli B.

1967 ◽  
Vol 25 ◽  
pp. 96-97
Author(s):  
Manfred E. Bayer
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Electron Microscope ◽  
Uranyl Acetate ◽  
E Coli ◽  
Receptor Sites ◽  
Rigid Cell Wall ◽  
Host Cell Surface ◽  
Bacterial Viruses ◽  
Escherichia Coli B

Bacterial viruses adsorb specifically to receptors on the host cell surface. Although the chemical composition of some of the cell wall receptors for bacteriophages of the T-series has been described and the number of receptor sites has been estimated to be 150 to 300 per E. coli cell, the localization of the sites on the bacterial wall has been unknown.When logarithmically growing cells of E. coli are transferred into a medium containing 20% sucrose, the cells plasmolize: the protoplast shrinks and becomes separated from the somewhat rigid cell wall. When these cells are fixed in 8% Formaldehyde, post-fixed in OsO4/uranyl acetate, embedded in Vestopal W, then cut in an ultramicrotome and observed with the electron microscope, the separation of protoplast and wall becomes clearly visible, (Fig. 1, 2). At a number of locations however, the protoplasmic membrane adheres to the wall even under the considerable pull of the shrinking protoplast. Thus numerous connecting bridges are maintained between protoplast and cell wall. Estimations of the total number of such wall/membrane associations yield a number of about 300 per cell.

Infection of Escherichia coli with bacteriophages

1969 ◽  
Vol 27 ◽  
pp. 370-371
Author(s):  
Manfred E. Bayer
Keyword(s):  
Escherichia Coli ◽  
Nucleic Acid ◽  
Cell Surface ◽  
Virus Type ◽  
Infection Process ◽  
Adsorption Site ◽  
The Other ◽  
Specific Receptors ◽  
Bacterial Receptors

The first step in the infection of a bacterium by a virus consists of a collision between cell and bacteriophage. The presence of virus-specific receptors on the cell surface will trigger a number of events leading eventually to release of the phage nucleic acid. The execution of the various "steps" in the infection process varies from one virus-type to the other, depending on the anatomy of the virus. Small viruses like ØX 174 and MS2 adsorb directly with their capsid to the bacterial receptors, while other phages possess attachment organelles of varying complexity. In bacteriophages T3 (Fig. 1) and T7 the small conical processes of their heads point toward the adsorption site; a welldefined baseplate is attached to the head of P22; heads without baseplates are not infective.

The Nature of the Intramembrane Particle

1980 ◽  
Vol 38 ◽  
pp. 688-691
Author(s):  
A.J. Verkleij
Keyword(s):  
Escherichia Coli ◽  
Tight Junction ◽  
Gap Junction ◽  
The Other ◽  
Fracture Face ◽  
Band 3 Protein ◽  
Satisfactory Explanation ◽  
Freeze Fracturing ◽  
Intramembrane Particle ◽  
Luminal Membrane

Freeze-fracturing splits membranes into two helves, thus allowing an examination of the membrane interior. The 5-10 rm particles visible on both monolayers are widely assumed to be proteinaceous in nature. Most membranes do not reveal impressions complementary to particles on the opposite fracture face, if the membranes are fractured under conditions without etching. Even if it is considered that shadowing, contamination or fracturing itself might obscure complementary pits', there is no satisfactory explanation why under similar physical circimstances matching halves of other membranes can be visualized. A prominent example of uncomplementarity is found in the erythrocyte manbrane. It is wall established that band 3 protein and possibly glycophorin represents these nonccmplanentary particles. On the other hand a number of membrane types show pits opposite the particles. Scme well known examples are the ";gap junction',"; tight junction, the luminal membrane of the bladder epithelial cells and the outer membrane of Escherichia coli.

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