scholarly journals A NEW MAP LOCATION FOR THE ilvB LOCUS OF ESCHERICHIA COLI

Genetics ◽  
1980 ◽  
Vol 96 (1) ◽  
pp. 59-77
Author(s):  
Thomas C Newman ◽  
Mark Levinthal
Keyword(s):  
Escherichia Coli ◽  
Structural Gene ◽  
Acetolactate Synthase ◽  
Deletion Mapping ◽  
Donor Strain ◽  
E Coli ◽  
Linkage Of Genes ◽  
Map Location ◽  
New Alleles

ABSTRACT We isolated, in E. coli K12, new alleles of the ilvB locus, the structural gene for acetolactate synthase isoenzyme I, and showed them to map at or near the ilvB619 site. The map position of the ilvB locus was redetermined because plasmids containing the ilvC-cya portion of the chromosome did not complement mutations at the ilvB locus. Furthermore, diploids for the ilvEDAC genes formed with these plasmids in an ilvHI background facilitated the isolation of the new ilvB alleles. The ilvB locus was remapped and found to be located at 81.5 minutes, between the uhp and dnaA loci. This location was determined by two- and three-point transductional crosses, deletion mapping and complementation with newly isolated plasmids. One of the new alleles of the ilvB gene is a mu-1 insertion. When present in the donor strain, this allele interferes with the linkage of genes flanking the mu-1 insertion, as well as the linkage of genes to either side of the mu-1 insertion.

scholarly journals Characterization and in Vivo Cloning of prlC, a Suppressor of Signal Sequence Mutations in Escherichia coli K12

Genetics ◽  
1987 ◽  
Vol 116 (4) ◽  
pp. 513-521
Author(s):  
Nancy J Trun ◽  
Thomas J Silhavy
Keyword(s):  
Escherichia Coli ◽  
Genetic Mapping ◽  
Signal Sequence ◽  
Illegitimate Recombination ◽  
Mutant Phenotype ◽  
E Coli ◽  
Physical Location ◽  
Sequence Deletion ◽  
New Alleles

ABSTRACT The prlC gene of E. coli was originally identified as an allele, prlC1, which suppresses certain signal sequence mutations in the genes for several exported proteins. We have isolated six new alleles of prlC that also confer this phenotype. These mutations can be placed into three classes based on the degree to which they suppress the lamBsignal sequence deletion, lamBs78. Genetic mapping reveals that the physical location of the mutations in prlC correlates with the strength of the suppression, suggesting that different regions of the gene can be altered to yield a suppressor phenotype. We also describe an in vivo cloning procedure using λplacMu9H. The procedure relies on transposition and illegitimate recombination to generate a specialized transducing phage that carries prlC1. This method should be applicable to any gene for which there is a mutant phenotype.

Co-Expression of Threonine Dehydratase and Acetolactate Synthase in Escherichia Coli for L-Isoleucine Production

2014 ◽  
Vol 989-994 ◽  
pp. 997-1002 ◽  
Author(s):  
Jian Wang ◽  
Jia Kai Sun ◽  
Qing Yang Xu
Keyword(s):  
Escherichia Coli ◽  
Corynebacterium Glutamicum ◽  
Carbon Flux ◽  
Batch Fermentation ◽  
Acetolactate Synthase ◽  
Fed Batch ◽  
Threonine Dehydratase ◽  
E Coli ◽  
Fed Batch Fermentation ◽  
Fermentation Period

Metabolic engineering ofCorynebacterium glutamicumhas sought to divert carbon into L-isoleucine. However, the fermentation period of this strain is long. TheC.glutamicumYILW strain (LeuL, AHVr, SGr, Leu-MEr) was previously derived by repeated compound mutagenesis which could accumulate 20.2 g/L L-isoleucine in a 5-L jar fermentor. Overexpression of the threonine dehydratase gene (ilvA) fromCorynebacterium glutamicumYILW and coexpression of threonine dehydratase and acetolactate synthase (ilvBN) from it were employed to divert carbon flux toward L-isoleucine. The strainE. coliTRFC with the expression ofilvA could accumulate L-isoleucine of 6.8 g/L without accumulation of any L-threonine by fed-batch fermentation in a 5-L jar fermentor. However, the production of L-isoleucine by the strainE.coliTRFC with the co-expression ofilvA andilvBN was decreased by 19.1%, and the production of L-valine was increased by 40% compared with that ofE. coliTRFC with the expression ofilvA.

scholarly journals Emergence of antibiotic resistance from multinucleated bacterial filaments

2014 ◽  
Vol 112 (1) ◽  
pp. 178-183 ◽  
Author(s):  
Julia Bos ◽  
Qiucen Zhang ◽  
Saurabh Vyawahare ◽  
Elizabeth Rogers ◽  
Susan M. Rosenberg ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Dna Repair ◽  
Antibiotic Resistance ◽  
Sos Response ◽  
Single Cell Level ◽  
Environmental Niche ◽  
Cell Level ◽  
E Coli ◽  
Enhanced Resistance ◽  
New Alleles

Bacteria can rapidly evolve resistance to antibiotics via the SOS response, a state of high-activity DNA repair and mutagenesis. We explore here the first steps of this evolution in the bacteriumEscherichia coli. Induction of the SOS response by the genotoxic antibiotic ciprofloxacin changes theE. colirod shape into multichromosome-containing filaments. We show that at subminimal inhibitory concentrations of ciprofloxacin the bacterial filament divides asymmetrically repeatedly at the tip. Chromosome-containing buds are made that, if resistant, propagate nonfilamenting progeny with enhanced resistance to ciprofloxacin as the parent filament dies. We propose that the multinucleated filament creates an environmental niche where evolution can proceed via generation of improved mutant chromosomes due to the mutagenic SOS response and possible recombination of the new alleles between chromosomes. Our data provide a better understanding of the processes underlying the origin of resistance at the single-cell level and suggest an analogous role to the eukaryotic aneuploidy condition in cancer.

scholarly journals Pilus-Mediated Adherence of Haemophilus influenzae to Human Respiratory Mucins

2000 ◽  
Vol 68 (6) ◽  
pp. 3362-3367 ◽  
Author(s):  
Martin Kubiet ◽  
Reuben Ramphal ◽  
Allan Weber ◽  
Arnold Smith
Keyword(s):  
Escherichia Coli ◽  
Haemophilus Influenzae ◽  
Lung Disease ◽  
Gene Cluster ◽  
Otitis Media ◽  
Structural Gene ◽  
Chronic Lung Disease ◽  
Type B ◽  
E Coli

ABSTRACT Haemophilus influenzae, especially the nontypeable strains, are among the most common pathogens encountered in patients with chronic lung disease and otitis media. We and others have demonstrated that respiratory isolates of nontypeable H. influenzae bind to human mucins, but the mechanism of binding is not entirely clear. We have therefore examined the role of pili in the adherence of both type b and nontypeable H. influenzae to human respiratory mucins. We used isogenic H. influenzaestrains with a mutation in the structural gene for pilin (hifA), a laboratory H. influenzae strain transformed with a type b pilus gene cluster (from strain C54), antibodies raised against H. influenzae HifA, andEscherichia coli strains carrying a cloned type b pilus gene cluster (from strain AM30) in these studies. All bacteria lacking HifA or the pilus gene cluster had decreased adherence of piliatedH. influenzae to mucins, and Fab fragments of anti-HifA antibodies inhibited the adherence. E. coli strains carrying the cloned type b pilus gene cluster were six to seven times more adhesive than strains carrying the vector. The role of other putative adhesins was not examined and thus cannot be excluded, but these studies support a role for pili in the binding of H. influenzae to human respiratory mucins.

scholarly journals Silent Mischief: Bacteriophage Mu Insertions Contaminate Products of Escherichia coli Random Mutagenesis Performed Using Suicidal Transposon Delivery Plasmids Mobilized by Broad-Host-Range RP4 Conjugative Machinery

2010 ◽  
Vol 192 (24) ◽  
pp. 6418-6427 ◽  
Author(s):  
Lionel Ferrières ◽  
Gaëlle Hémery ◽  
Toan Nham ◽  
Anne-Marie Guérout ◽  
Didier Mazel ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Host Range ◽  
Random Mutagenesis ◽  
Broad Host Range ◽  
Donor Strain ◽  
Bacteriophage Mu ◽  
Genetic Determinants ◽  
Sensitive Species ◽  
E Coli ◽  
Original Construction

ABSTRACT Random transposon mutagenesis is the strategy of choice for associating a phenotype with its unknown genetic determinants. It is generally performed by mobilization of a conditionally replicating vector delivering transposons to recipient cells using broad-host-range RP4 conjugative machinery carried by the donor strain. In the present study, we demonstrate that bacteriophage Mu, which was deliberately introduced during the original construction of the widely used donor strains SM10 λpir and S17-1 λpir, is silently transferred to Escherichia coli recipient cells at high frequency, both by hfr and by release of Mu particles by the donor strain. Our findings suggest that bacteriophage Mu could have contaminated many random-mutagenesis experiments performed on Mu-sensitive species with these popular donor strains, leading to potential misinterpretation of the transposon mutant phenotype and therefore perturbing analysis of mutant screens. To circumvent this problem, we precisely mapped Mu insertions in SM10 λpir and S17-1 λpir and constructed a new Mu-free donor strain, MFDpir, harboring stable hfr-deficient RP4 conjugative functions and sustaining replication of Π-dependent suicide vectors. This strain can therefore be used with most of the available transposon-delivering plasmids and should enable more efficient and easy-to-analyze mutant hunts in E. coli and other Mu-sensitive RP4 host bacteria.

scholarly journals Cloning, Sequencing, and Role in Serum Susceptibility of Porin II from Mesophilic Aeromonas hydrophila

2000 ◽  
Vol 68 (4) ◽  
pp. 1849-1854 ◽  
Author(s):  
Maria Mercé Nogueras ◽  
Susana Merino ◽  
Alicia Aguilar ◽  
Vicente Javier Benedi ◽  
Juan M. Tomás
Keyword(s):  
Escherichia Coli ◽  
Structural Gene ◽  
Aeromonas Hydrophila ◽  
Surface Molecule ◽  
E Coli ◽  
Genetic Position ◽  
O 11 ◽  
Insertion Mutants

ABSTRACT We cloned and sequenced the structural gene for Aeromonas hydrophila porin II from strain AH-3 (serogroup O:34). The genetic position of this gene, like that of ompF inEscherichia coli, is adjacent to aspC and transcribed in the same direction. However, upstream of the porin II gene no similarities with E. coli were found. We obtained defined insertion mutants in porin II gene either in A. hydrophila (O:34) or A. veronii sobria (serogroup O:11) serum-resistant or -sensitive strains. Furthermore, we complemented these mutants with a plasmid harboring only the porin II gene, which allowed us to define the role of porin II as an important surface molecule involved in serum susceptibility and C1q binding in these strains.

DELETION MAPPING OF zwf, THE GENE FOR A CONSTITUTIVE ENZYME, GLUCOSE 6-PHOSPHATE DEHYDROGENASE IN ESCHERICHIA COLI

Genetics ◽  
1972 ◽  
Vol 71 (4) ◽  
pp. 481-489
Author(s):  
D G Fraenkel ◽  
Santimoy Banerjee
Keyword(s):  
Escherichia Coli ◽  
Fine Structure ◽  
Mutant Strain ◽  
Genetic Map ◽  
Gene Order ◽  
Sugar Metabolism ◽  
Deletion Mapping ◽  
Secondary Mutation ◽  
E Coli ◽  
Glucose 6 Phosphate Dehydrogenase

ABSTRACT Genes for three enzymes of intermediary sugar metabolism in E. coli, zwf (glucose 6-phosphate dehydrogenase, constitutive), edd (gluconate 6-phosphate dehydrase, inducible), and eda (2-keto-3-deoxygluconate 6-phosphate aldolase, differently inducible) are closely linked on the E. coli genetic map, the overall gene order being man… old… eda. edd. zwf… cheB… uvrC… his. One class of apparent revertants of an eda mutant strain contains a secondary mutation in edd, and some of these mutations are deletions extending into zwf. We have used a series of spontaneous edd-zwf deletions to map a series of point mutants in zwf and thus report the first fine structure map of a gene for a constitutive enzyme (zwf).

scholarly journals Pathogenicity of an EnterotoxigenicEscherichia coli Hemolysin (hlyA) Mutant in Gnotobiotic Piglets

1998 ◽  
Vol 66 (10) ◽  
pp. 5031-5035 ◽  
Author(s):  
Rodney A. Moxley ◽  
Emil M. Berberov ◽  
David H. Francis ◽  
Jun Xing ◽  
Mahtab Moayeri ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Structural Gene ◽  
Intestinal Infection ◽  
E Coli ◽  
Oral Inoculation ◽  
Gnotobiotic Piglet ◽  
Gnotobiotic Piglets

ABSTRACT Pigs infected with hemolytic F4+ strains of enterotoxigenic Escherichia coli often develop septicemia secondary to intestinal infection. We tested the hypothesis that inactivation of hemolysin would reduce the ability of F4+enterotoxigenic E. coli to cause septicemia in swine following oral inoculation. Inactivation of the hemolysin structural gene (hlyA) did not decrease the incidence of septicemia in the gnotobiotic piglet model.

scholarly journals Model System To Evaluate the Effect of ampD Mutations on AmpC-Mediated β-Lactam Resistance

2006 ◽  
Vol 50 (6) ◽  
pp. 2030-2037 ◽  
Author(s):  
Amber J. Schmidtke ◽  
Nancy D. Hanson
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Structural Gene ◽  
Model System ◽  
Alternative Mechanism ◽  
Citrobacter Freundii ◽  
E Coli ◽  
K 12 ◽  
Carboxy Terminal ◽  
The Impact

ABSTRACT Mutations within the structural gene of ampD can lead to AmpC overproduction and increases in β-lactam MICs in organisms with an inducible ampC. However, identification of mutations alone cannot predict the impact that those mutations have on AmpD function. Therefore, a model system was designed to determine the effect of ampD mutations on ceftazidime MICs using an AmpD− mutant Escherichia coli strain which produced an inducible plasmid-encoded AmpC. ampD genes were amplified by PCR from strains of E. coli, Citrobacter freundii, and Pseudomonas aeruginosa. Also, carboxy-terminal truncations of C. freundii ampD genes were constructed representing deletions of 10, 21, or 25 codons. Amplified ampD products were cloned into pACYC184 containing inducible bla ACT-1-ampR. Plasmids were transformed into E. coli strains JRG582 (AmpD−) and K-12 259 (AmpD+). The strains were evaluated for a derepressed phenotype using ceftazidime MICs. Some mutated ampD genes, including the ampD gene of a derepressed C. freundii isolate, resulted in substantial decreases in ceftazidime MICs (from >256 μg/ml to 12 to 24 μg/ml) for the AmpD− strain, indicating no role for these mutations in derepressed phenotypes. However, ampD truncation products and ampD from a partially derepressed P. aeruginosa strain resulted in ceftazidime MICs of >256 μg/ml, indicating a role for these gene modifications in derepressed phenotypes. The use of this model system indicated that alternative mechanisms were involved in the derepressed phenotype observed in strains of C. freundii and P. aeruginosa. The alternative mechanism involved in the derepressed phenotype of the C. freundii isolate was downregulation of ampD transcription.

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