scholarly journals Tracy Morton Sonneborn, 19 October 1905 - 26 January 1981

1982 ◽  
Vol 28 ◽  
pp. 537-574 ◽  
Keyword(s):  
Escherichia Coli ◽  
Molecular Biology ◽  
Genetic Recombination ◽  
Genetic Research ◽  
Sexual Cycle ◽  
Mating Types ◽  
Research Assistant ◽  
E Coli ◽  
Living Things ◽  
Modern Molecular Biology

The explosive development of genetics and molecular biology that we are now witnessing had its origin, some 40 years ago, in the introduction into genetic research of microorganisms. Compared with the higher animals and plants which had been used previously— Drosophila , maize, mice, etc.— microorganisms had many technical advantages, and as everyone knows, since then genetics has advanced prodigiously. Moreover, in spite of the extraordinary complexity of modern molecular biology, one thing stands out: basically the same genetic principles apply to the whole range of living things, from viruses to man. Everywhere the nuclear elements —ultimately DNA—play an overwhelmingly important role. The microorganisms first used in genetic research were a fungus— Neurospora ,a bacterium— Escherichia coli , and the bacteriophages of E. coli . However, long before these were used, another group of microorganisms—the protozoa—had been considered as potentially suitable. They were unicellular, and unlike bacteria, often had a regular sexual cycle. H. S. Jennings tried for many years to do genetics with the ciliate Paramecium but had little success, owing to difficulties in making controlled hybridizations between genetically diverse lines—an essential minimum desideratum for classical genetic work. In 1930 Jennings employed a young research assistant, T. M. Sonneborn, for the Paramecium work, and as a result, after 7 years, mating types were discovered in P. aurelia . Thereafter genetics along Mendelian lines with the organism became technically feasible. This was ten years before Lederberg and Tatum demonstrated that genetic recombination could occur in E. coli .

THE INFLUENCE OF THE PO1A1 MUTATION UPON RECOMBINATION IN ESCHERICHIA COLI K12

1979 ◽  
Vol 21 (3) ◽  
pp. 423-428 ◽  
Author(s):  
Barry W. Glickman ◽  
Tineke Rutgers
Keyword(s):  
Escherichia Coli ◽  
Dna Polymerase ◽  
Genetic Recombination ◽  
Dna Polymerase I ◽  
Multiple Gene ◽  
E Coli ◽  
Recombinational Process ◽  
K 12 ◽  
Polymerase I

Genetic recombination in Escherichia coli is a highly regulated process involving multiple gene products. We have investigated the role of DNA polymerase I in this process by studying the effect of the po1A1 mutation upon DNA transfer and conjugation in otherwise isogenic suppressor-free strains of E. coli K-12. It was found that the po1A1 mutation greatly reduces recombination in Hfr crosses (a factor of 20 in Po1+ × Po1A1 crosses and more than a factor of 100 in Po1A1 × Po1A1 crosses). However, since the po1A1 mutation reduces the strains capacity to act as a recipient for an F-prime and the analysis of recombination transfer gradients revealed no differences between Po1+ and Po1− strains, it is concluded that DNA polymerase I probably affects the transfer and/or stability of donor DNA rather than the recombinational process itself.

scholarly journals EXPERIMENTAL GENETIC RECOMBINATION IN VIVO BETWEEN ESCHERICHIA COLI AND SALMONELLA TYPHIMURIUM

1961 ◽  
Vol 114 (1) ◽  
pp. 141-148 ◽  
Author(s):  
H. Schneider ◽  
Samuel B. Formal ◽  
L. S. Baron
Keyword(s):  
Escherichia Coli ◽  
Salmonella Typhimurium ◽  
Intestinal Tract ◽  
Genetic Recombination ◽  
Mammalian Host ◽  
Experimental Conditions ◽  
E Coli

Antibiotic-pretreated mice were fed orally an Hfr culture of streptomycin-resistant E. coli and 1 day later, a streptomycin-resistant F- S. typhimurium culture. Hybrids were recovered in relatively small numbers from the feces of these mice within 24 hours demonstrating that genetic recombination can occur within the intestinal tract of a mammalian host under experimental conditions. These hybrids multiplied rapidly and persisted throughout the course of the experiment. In addition, hybrids were recovered which had not been observed in single matings performed in vitro.

scholarly journals Measurements of translation initiation from all 64 codons inE. coli

2016 ◽  
Author(s):  
Ariel Hecht ◽  
Jeff Glasgow ◽  
Paul R. Jaschke ◽  
Lukmaan Bawazer ◽  
Matthew S. Munson ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Protein Synthesis ◽  
Molecular Biology ◽  
Translation Initiation ◽  
Biological Systems ◽  
Start Codon ◽  
Living Matter ◽  
E Coli ◽  
Natural And Synthetic

ABSTRACTOur understanding of translation is one cornerstone of molecular biology that underpins our capacity to engineer living matter. The canonical start codon (AUG) and a few near-cognates (GUG, UUG) are typically considered as the “start codons” for translation initiation inEscherichia coli(E. coli). Translation is typically not thought to initiate from the 61 remaining codons. Here, we systematically quantified translation initiation inE. colifrom all 64 triplet codons. We detected protein synthesis above background initiating from at least 46 codons. Translation initiated from these non-canonical start codons at levels ranging from 0.01% to 2% relative to AUG. Translation initiation from non-canonical start codons may contribute to the synthesis of peptides in both natural and synthetic biological systems

scholarly journals Molecular evolution of the Escherichia coli chromosome. I. Analysis of structure and natural variation in a previously uncharacterized region between trp and tonB.

Genetics ◽  
1988 ◽  
Vol 120 (2) ◽  
pp. 345-358
Author(s):  
A Stoltzfus ◽  
J F Leslie ◽  
R Milkman
Keyword(s):  
Escherichia Coli ◽  
Large Scale ◽  
Natural Variation ◽  
Genetic Recombination ◽  
Coli Strain ◽  
Open Reading Frames ◽  
Dna Rearrangements ◽  
E Coli ◽  
Wild Strains ◽  
Reading Frames

Abstract We present the sequence of a 3500-bp region of the Escherichia coli strain K12 chromosome lying between the tryptophan operon and the tonB gene. Analysis of the sequence yields six open reading frames that have properties characteristic of genes for proteins. The reading frames are closely spaced, and putative transcription units and control sites compose over 95% of the DNA. The sequences of several wild strains of E. coli have been determined for a large segment of the region described. Comparison of these sequences reveals the effects of base substitutions, DNA rearrangements, and recombination. In the regions presumably expressed as polypeptides, most of the natural variation results from synonymous substitutions. However, the DNA rearrangements identified have end points within the open reading frames and disrupt them in a variety of ways. The effects of genetic recombination between strains, recently found to be significant on a large scale in E. coli, are also apparent in the region between trp and tonB.

The Central Importance of E. coli and λ‎ Phage in the New Molecular Biology

2021 ◽  
pp. 130-135
Author(s):  
Thomas E. Schindler
Keyword(s):  
Molecular Biology ◽  
Genetic Recombination ◽  
Model Organism ◽  
Restriction Enzymes ◽  
Model Organisms ◽  
Host Restriction ◽  
E Coli ◽  
Jumping Genes ◽  
K 12 ◽  
Convenient Model

This chapter considers two of the most important legacies of the Lederbergs’ pioneering work: the discoveries of the model organisms that would dominate molecular biology, E. coli and λ‎ bacteriophage. The Lederbergs’ introduction of E. coli as a convenient model organism shifted the direction of molecular genetics. Barbara McClintock’s discovery of jumping genes remained unappreciated for decades, until the field of molecular biology caught up to validate her transposable elements in bacteria. The discovery of restriction enzymes—the molecular scissors for precisely cutting DNA at specific sites, a prerequisite for genetic recombination techniques—emphasized the versatility of bacteriophage λ‎ as a powerful experimental tool. The discovery of specialized transduction by Larry Morse and Esther Lederberg hinted at the mechanisms of “host restriction.” Werner Arber and Daisy Dussoix discovered restriction endonucleases by building upon Esther Lederberg’s research with λ‎ phage and the differences between E. coli B and K-12.

scholarly journals SOME GENETIC CONSEQUENCES OF CHANGES IN THE LEVEL OF recA GENE FUNCTION IN ESCHERICHIA COLI K-12

Genetics ◽  
1976 ◽  
Vol 84 (4) ◽  
pp. 675-695
Author(s):  
Robert G Lloyd ◽  
Brooks Low
Keyword(s):  
Escherichia Coli ◽  
Gene Function ◽  
Genetic Recombination ◽  
Unit Length ◽  
Reca Gene ◽  
E Coli ◽  
Low Level ◽  
Transfer Origin ◽  
K 12

ABSTRACT Genetic recombination was studied in E. coli mutants that carry lesions in the recA gene but retain some capacity for generating recombinant progeny. We observed that recombination was detectable only at a very low level during the incubation of leaky RecA- merozygotes in broth. However, recombination appeared to occur at much higher frequencies when recombinant progeny were assayed by selection on minimal agar. Analysis of the recombinants obtained with Hfr donors revealed a deficiency of multiple exchanges per unit length of DNA in leaky RecA- strains. In many of these crosses recombinants that inherited donor alleles close to the transfer origin were much reduced in frequency, except when the recipient was also RecB-.

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.

Electron Microscopy and image analysis of nucleo-protein complexes

1994 ◽  
Vol 52 ◽  
pp. 88-89
Author(s):  
E. H. Egelman ◽  
X. Yu
Keyword(s):  
Electron Microscopy ◽  
Image Analysis ◽  
Normal Cell ◽  
Genetic Recombination ◽  
Protein Complexes ◽  
Chromosomal Rearrangements ◽  
Reca Protein ◽  
E Coli ◽  
Helical Polymer ◽  
Specific Protease

The RecA protein of E. coli has been shown to mediate genetic recombination, regulate its own synthesis, control the expression of other genes, act as a specific protease, form a helical polymer and have an ATPase activity, among other observed properties. The unusual filament formed by the RecA protein on DNA has not previously been shown to exist outside of bacteria. Within this filament, the 36 Å pitch of B-form DNA is extended to about 95 Å, the pitch of the RecA helix. We have now establishedthat similar nucleo-protein complexes are formed by bacteriophage and yeast proteins, and availableevidence suggests that this structure is universal across all of biology, including humans. Thus, understanding the function of the RecA protein will reveal basic mechanisms, in existence inall organisms, that are at the foundation of general genetic recombination and repair.Recombination at this moment is assuming an importance far greater than just pure biology. The association between chromosomal rearrangements and neoplasms has become stronger and stronger, and these rearrangements are most likely products of the recombinatory apparatus of the normal cell. Further, damage to DNA appears to be a major cause of cancer.

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