Recombination-deficient mutations and thymineless death in Escherichia coli K12: reciprocal effects of recBC and recF and indifference of recA mutations

1982 ◽  
Vol 28 (4) ◽  
pp. 425-430 ◽  
Author(s):  
Hiroaki Nakayama ◽  
Koji Nakayama ◽  
Ritsuko Nakayama ◽  
Yasuko Nakayama
Keyword(s):  
Escherichia Coli ◽  
Reciprocal Effects ◽  
Gene Products ◽  
Escherichia Coli K12 ◽  
Thymineless Death ◽  
Lethal Event ◽  
Increased Sensitivity ◽  
Per Se ◽  
Cellular Dna ◽  
Reca Mutation

In an approach to characterizing the nature of the lethal event in thymineless death (TLD), rec mutants of Escherichia coli K12 were examined for their sensitivity to TLD. The recB21 and recC22 mutations sensitized cells of the AB1157 line to TLD but not cells of the HF4733 line. This increased sensitivity was not suppressed substantially by either sbcB15 or xonA1 mutation. In contrast, a recF mutation appeared to make cells more resistant to TLD than rec+ cells. Three different recA alleles were shown not to affect TLD appreciably. These results not only provide further support for the view that the site of the lethal event in TLD is cellular DNA, but also strongly suggest the involvement of the recBC and recF gene products in TLD. The apparent indifference of recA mutation implies that the conventional recombination and repair pathways per se are not involved in TLD and that the hypothetical lethal damage to DNA may be unique in nature.

Suppression by the ColV,I-K94 plasmid of inhibitor sensitivities in ompA mutants of Escherichia coli

1988 ◽  
Vol 34 (2) ◽  
pp. 148-156 ◽  
Author(s):  
Claudia F. L. Reakes ◽  
Caroline M. M. Deeney ◽  
Margaret Goodson ◽  
Robin J. Rowbury
Keyword(s):  
Escherichia Coli ◽  
Cell Surface ◽  
Fusidic Acid ◽  
Polymyxin B ◽  
Aminoglycoside Antibiotics ◽  
The Other ◽  
Gene Products ◽  
Escherichia Coli K12 ◽  
Increased Sensitivity ◽  
Large Plasmids

A series of ompA mutants derived from Escherichia coli K12 strains showed increased sensitivity (compared with the ompA+ parents) to aminoglycoside antibiotics and to other cationic agents including polymyxin B. One tested mutant also showed increased sensitivity to nafcillin and fusidic acid, but not to the hydrophilic ampicillin. All these inhibitor sensitivities in the ompA mutants were suppressed by ColV, I-K94 and by certain other ColV plasmids, but not by any of the other tested large plasmids. Suppression correlated with the production of the VmpA protein, but transfer and colicin components were not needed for suppression. Further comparison of the ompA and vmpA genes and their products was made and it indicated that there is little if any homology between the genes, that the synthesis of their products is regulated by quite different mechanisms, and that regions of these gene products exposed at the cell surface show different susceptibility to protease attack after denaturation.

Evidence for two recA genes mediating DNA repair in Bacillus megaterium

Microbiology ◽  
2005 ◽  
Vol 151 (3) ◽  
pp. 775-787 ◽  
Author(s):  
Hannes Nahrstedt ◽  
Christine Schröder ◽  
Friedhelm Meinhardt
Keyword(s):  
Escherichia Coli ◽  
Dna Repair ◽  
Mitomycin C ◽  
Bacillus Megaterium ◽  
Functional Complementation ◽  
Homologous Gene ◽  
Gene Products ◽  
Null Mutant ◽  
Promoter Regions ◽  
Increased Sensitivity

Isolation and subsequent knockout of a recA-homologous gene in Bacillus megaterium DSM 319 resulted in a mutant displaying increased sensitivity to mitomycin C. However, this mutant did not exhibit UV hypersensitivity, a finding which eventually led to identification of a second functional recA gene. Evidence for recA duplicates was also obtained for two other B. megaterium strains. In agreement with potential DinR boxes located within their promoter regions, expression of both genes (recA1 and recA2) was found to be damage-inducible. Transcription from the recA2 promoter was significantly higher than that of recA1. Since a recA2 knockout could not be achieved, functional complementation studies were performed in Escherichia coli. Heterologous expression in a RecA null mutant resulted in increased survival after UV irradiation and mitomycin C treatment, proving both recA gene products to be functional in DNA repair. Thus, there is evidence for an SOS-like pathway in B. megaterium that differs from that of Bacillus subtilis.

Amplification of the put genes and identification of the put gene products in Escherichia coli K12

1980 ◽  
Vol 58 (10) ◽  
pp. 787-796 ◽  
Author(s):  
Janet M. Wood ◽  
David Zadworny
Keyword(s):  
Escherichia Coli ◽  
Dehydrogenase Activity ◽  
Gene Products ◽  
Proline Dehydrogenase ◽  
Transport Activity ◽  
E Coli ◽  
Proline Transport ◽  
Escherichia Coli K12 ◽  
Biochemical Assays ◽  
Transport Defect

The utilization of L-proline as carbon or nitrogen source for the growth of Escherichia coli K12 requires the activities of an L-proline porter (PP-I) and a bifunctional L-proline dehydrogenase – Δ1-pyrroline carboxylate dehydrogenase. PP-I is inactivated by mutations at putP and the bifunctional dehydrogenase is encoded in the adjacent locus, putA, at 22 min on the chromosome map. Two additional loci, proP (at 92 min) and proT (at 82 min), have also been implicated in L-proline transport. We have studied four ColE1/E. coli K12 hybrid plasmids from the plasmid bank prepared by Clarke and Carbon. Each of these plasmids was shown previously to complement an L-proline transport defect in E. coli. Genetic complementation analysis and biochemical assays of L-proline transport and L-proline dehydrogenase activity show that three of these hybrid plasmids bear the putPA region of the E. coli chromosome (plasmids pLC4-45, pLC10-29, and pLC43-41). The fourth plasmid, pLC35-38, specifically enhances the L-proline transport activity of its host bacteria but not their L-proline dehydrogenase activity. It probably encodes putP. We have used these plasmids in an E. coli minicell system to identify the putA and putP gene products.

Thymineless Death in Recombination Deficient Mutants of Escherichia coli K12

1980 ◽  
Vol 35 (3-4) ◽  
pp. 279-283 ◽  
Author(s):  
S. I. Ahmad
Keyword(s):  
Escherichia Coli ◽  
Dna Damage ◽  
Mutant Strain ◽  
Synthetic Medium ◽  
Single Strand ◽  
Strand Breaks ◽  
Escherichia Coli K12 ◽  
Single Strand Breaks ◽  
Respective Parent ◽  
Thymineless Death

Abstract When grown in thymine-free minimal synthetic medium, thyA recA mutants of Escherichia coli K12 were comparatively more resistant and thyA recBC mutants more sensitive to thymineless death (TLD) than their respective parent strains. No excessive numbers of single-strand breaks were observed in the DNA of the recBC mutant strain starved for thymine, hence the hypersensi­ tivity for TLD in this strain was not caused by this type of DNA damage. Although experiments were performed with the same recBC mutant strain as used by earlier workers, results presented here contradict earlier findings that recBC mutants are no more sensitive and recA mutants are no more resistant to TLD.

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