HIGH FREQUENCY OF GENETIC DUPLICATIONS IN THE dnaB REGION OF THE ESCHERICHIA COLI K12 CHROMOSOME

Genetics ◽  
1981 ◽  
Vol 98 (4) ◽  
pp. 677-689
Author(s):  
Robert A Sclafani ◽  
James A Wechsler
Keyword(s):  
Escherichia Coli ◽  
High Frequency ◽  
Cell Populations ◽  
E Coli ◽  
Escherichia Coli K12 ◽  
Recombination System ◽  
Tn10 Insertion ◽  
Insertion Mutants

ABSTRACT The region that includes the dnaB locus on the E. coli K12 chromosome was shown to be duplicated at high frequency in cell populations. The duplications were shown to be arranged in tandem and segregated at various frequencies. Segregation was dependent on the recA recombination system, but independent of recB,C. Though most of the data was obtained with dnaB::Tn10 insertion mutants, the duplications were shown to occur in the absence of Tn10.

scholarly journals Bacteriophage Lambda: a Paradigm Revisited

2010 ◽  
Vol 84 (13) ◽  
pp. 6876-6879 ◽  
Author(s):  
Paul C. M. Fogg ◽  
Heather E. Allison ◽  
Jon R. Saunders ◽  
Alan J. McCarthy
Keyword(s):  
Escherichia Coli ◽  
Sequence Analysis ◽  
High Frequency ◽  
Southern Hybridization ◽  
Integration Site ◽  
Bacteriophage Lambda ◽  
Rare Event ◽  
Low Frequency ◽  
E Coli ◽  
Very Low Frequency

ABSTRACT Bacteriophage lambda has an archetypal immunity system, which prevents the superinfection of its Escherichia coli lysogens. It is now known that superinfection can occur with toxigenic lambda-like phages at a high frequency, and here we demonstrate that the superinfection of a lambda lysogen can lead to the acquisition of additional lambda genomes, which was confirmed by Southern hybridization and quantitative PCR. As many as eight integration events were observed but at a very low frequency (6.4 × 10−4) and always as multiple insertions at the established primary integration site in E. coli. Sequence analysis of the complete immunity region demonstrated that these multiply infected lysogens were not immunity mutants. In conclusion, although lambda superinfection immunity can be confounded, it is a rare event.

scholarly journals Occurrence of Virulence Genes Associated with Diarrheagenic Pathotypes in Escherichia coli Isolates from Surface Water

2012 ◽  
Vol 79 (1) ◽  
pp. 328-335 ◽  
Author(s):  
Jatinder P. S. Sidhu ◽  
Warish Ahmed ◽  
Leonie Hodgers ◽  
Simon Toze
Keyword(s):  
Escherichia Coli ◽  
Health Risks ◽  
High Frequency ◽  
Aquatic Ecosystems ◽  
Virulence Genes ◽  
Storm Water ◽  
Storm Events ◽  
Widespread Occurrence ◽  
Content Type ◽  
E Coli

ABSTRACTEscherichia coliisolates (n= 300) collected from six sites in subtropical Brisbane, Australia, prior to and after storm events were tested for the presence of 11 virulence genes (VGs) specific to diarrheagenic pathotypes. The presence ofeaeA,stx1,stx2, andehxAgenes specific for the enterohemorrhagicE. coli(EHEC) pathotype was detected in 56%, 6%, 10%, and 13% of isolates, respectively. The VGsastA(69%) andaggR(29%), carried by enteroaggregative (EAEC) pathotypes, were frequently detected inE. coliisolates. The enteropathogenicE. coli(EPEC) genebfpwas detected in 24% of isolates. In addition, enteroinvasiveE. coli(EIEC) VGipaHwas also detected in 14% of isolates. During dry periods, isolates belonging to the EAEC pathotype were most commonly detected (23%), followed by EHEC (11%) and EPEC (11%). Conversely, a more uniform prevalence of pathotypes, EPEC (14%), EAEC (12%), EIEC (10%), EHEC (7%), and ETEC (7%), was observed after the storm events. The results of this study highlight the widespread occurrence of potentially diarrheagenic pathotypes in the urban aquatic ecosystems. While the presence of VGs inE. coliisolates alone is insufficient to determine pathogenicity, the presence of diarrheagenicE. colipathotypes in high frequency after the storm events could lead to increased health risks if untreated storm water were to be used for nonpotable purposes and recreational activities.

scholarly journals The Listeria monocytogenes Homolog of the Escherichia coli era Gene Is Involved in Adhesion to Inert Surfaces

2007 ◽  
Vol 73 (23) ◽  
pp. 7789-7792 ◽  
Author(s):  
Frédéric Auvray ◽  
Danielle Chassaing ◽  
Cécile Duprat ◽  
Brigitte Carpentier
Keyword(s):  
Escherichia Coli ◽  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Growth Defect ◽  
Cell Populations ◽  
Lower Growth ◽  
E Coli ◽  
Attached Cell ◽  
Dimethylammonium Chloride ◽  
Inert Surfaces

ABSTRACT Two transposon-insertional mutants of Listeria monocytogenes showing smaller viable surface-attached cell populations after disinfection with N,N-didecyl-N,N-dimethylammonium chloride were identified. In both mutants, transposon Tn917-lac was found to be inserted into the same gene, lmo1462, which is homologous to the essential Escherichia coli era gene. Both L. monocytogenes lmo1462-disrupted mutants displayed lower growth rates, as was also shown for several E. coli era mutants, and the lmo1462 gene was able to complement the growth defect of an E. coli era mutant. We showed that the disruption of lmo1462 decreased the ability of L. monocytogenes cells to adhere to stainless steel. Our results suggest that this era-like gene is involved in adhesion and contributes to the presence of L. monocytogenes on surfaces.

scholarly journals High Frequency of Diarrheagenic Escherichia coli in HIV-Infected Patients and Patients with Thalassemia in Kerman, Iran

2015 ◽  
Vol 16 (4) ◽  
pp. 353-358 ◽  
Author(s):  
Hesam Alizade ◽  
Hamid Sharifi ◽  
Zahedeh Naderi ◽  
Reza Ghanbarpour ◽  
Mehdi Bamorovat ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Polymerase Chain Reaction ◽  
Statistical Analysis ◽  
High Frequency ◽  
Multiplex Polymerase Chain Reaction ◽  
Chain Reaction ◽  
Fecal Samples ◽  
E Coli ◽  
Diarrheagenic Escherichia Coli ◽  
Polymerase Chain

This study was conducted on patients with thalassemia and HIV-infected patients to determine the frequency of diarrheagenic Escherichia coli in Kerman, Iran. We analyzed 68 and 49 E coli isolates isolated from healthy fecal samples of patients with thalassemia and HIV-infected patients, respectively. The E coli isolates were studied using a multiplex polymerase chain reaction to identify the enterotoxigenic E coli (ETEC), enterohemorrhagic E coli (EHEC), and enteropathogenic E coli (EPEC) groups. Statistical analysis was carried out to determine the correlation of diarrheagenic E coli between HIV-infected patients and patients with thalassemia using Stata 11.2 software. The frequency of having at least 1 diarrheagenic E coli was more common in patients with thalassemia (67.64%) than in HIV-infected patients (57.14%; P = .25), including ETEC (67.64% versus 57.14%), EHEC (33.82% versus 26.53%), and EPEC (19.11% versus 16.32%). The results of this study indicate that ETEC, EHEC, and EPEC pathotypes are widespread among diarrheagenic E coli isolates in patients with thalassemia and HIV-infected patients.

scholarly journals Enzymic synthesis of N-acetyl-l-phenylalanine in Escherichia coli K12

1971 ◽  
Vol 124 (5) ◽  
pp. 905-913 ◽  
Author(s):  
R. V. Krishna ◽  
P. R. Krishnaswamy ◽  
D. Rajagopal Rao
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Amino Acid ◽  
Substrate Specificity ◽  
Acetyl Coa ◽  
Ph Optimum ◽  
E Coli ◽  
Enzymic Synthesis ◽  
Escherichia Coli K12

1. Cell-free extracts of Escherichia coli K12 catalyse the synthesis of N-acetyl-l-phenylalanine from acetyl-CoA and l-phenylalanine. 2. The acetyl-CoA–l-phenylalanine α-N-acetyltransferase was purified 160-fold from cell-free extracts. 3. The enzyme has a pH optimum of 8 and catalyses the acetylation of l-phenylalanine. Other l-amino acids such as histidine and alanine are acetylated at slower rates. 4. A transacylase was also purified from E. coli extracts and its substrate specificity studied. 5. The properties of both these enzymes were compared with those of other known amino acid acetyltransferases and transacylases.

scholarly journals Growth of cell wall-defective variants of Escherichia coli: comparison of aerobic and anaerobic induction frequencies

1977 ◽  
Vol 6 (2) ◽  
pp. 166-171
Author(s):  
T W Huber ◽  
A W Brinkley
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
High Frequency ◽  
Anaerobic Incubation ◽  
Anaerobic Conditions ◽  
Group Iii ◽  
E Coli ◽  
Induction Frequency ◽  
Group I ◽  
Aerobic And Anaerobic

A method for quantitating the conversion of Escherichia coli to colony-forming, cell wall-defective (CWD) bacteria has been developed. The induction frequency, i.e., the percentage of the population recovered as CWD colonies was determined for 20 randomly selected clinical isolates of E. coli under aerobic and anaerobic incubation conditions. Penicillin (1,000 U/ML) was the inducing agent. The 20 strains segregated into three groups. Group I organisms produced CWD colonies with high frequency both aerobically and anaerobically. Grout II organisms showed a much higher induction frequency anaerobically than aerobically. Group III organisms were poor inducers. Thirty percent of the strains were group I, 50% were group II, and 20% were group III organisms. These data indicate that anaerobic conditions enhance the induction and growth of CWD E. coli in the research laboratory and suggest that anaerobic incubation may be important in recovery of medically significant CWD bacteria.

scholarly journals Sequence Analysis of Tn10 Insertion Sites in a Collection of Escherichia coli Strains Used for Genetic Mapping and Strain Construction

1998 ◽  
Vol 180 (23) ◽  
pp. 6408-6411 ◽  
Author(s):  
Brian P. Nichols ◽  
Obaid Shafiq ◽  
Victoria Meiners
Keyword(s):  
Escherichia Coli ◽  
Sequence Analysis ◽  
Hot Spots ◽  
Insertion Site ◽  
Inverse Pcr ◽  
E Coli ◽  
Chromosome Sequence ◽  
Tn10 Insertion ◽  
Insertion Sites ◽  
Recombination Hot Spots

ABSTRACT The chromosomal insertion sites of Tn10-containingEscherichia coli strains were amplified by inverse PCR, and the nucleotide sequences of the junctions were determined. In 95 strains analyzed, 88 unique Tn10 positions were determined and matched to the E. coli chromosome sequence. Two gaps in insertion site positions were noted, one including the terminus of DNA replication and another bounded by recombination hot spots RhsA and RhsB.

scholarly journals Integrated Genomic Map from Uropathogenic Escherichia coli J96

2000 ◽  
Vol 68 (10) ◽  
pp. 5933-5942 ◽  
Author(s):  
Lyla J. Melkerson-Watson ◽  
Christopher K. Rode ◽  
Lixin Zhang ◽  
Betsy Foxman ◽  
Craig A. Bloch
Keyword(s):  
Escherichia Coli ◽  
Virulence Genes ◽  
Housekeeping Genes ◽  
E Coli ◽  
Restriction Sites ◽  
Physical And Genetic Map ◽  
K 12 ◽  
Genomic Map ◽  
Insertion Mutants

ABSTRACT Escherichia coli J96 is a uropathogen having both broad similarities to and striking differences from nonpathogenic, laboratoryE. coli K-12. Strain J96 contains three large (>100-kb) unique genomic segments integrated on the chromosome; two are recognized as pathogenicity islands containing urovirulence genes. Additionally, the strain possesses a fourth smaller accessory segment of 28 kb and two deletions relative to strain K-12. We report an integrated physical and genetic map of the 5,120-kb J96 genome. The chromosome contains 26 NotI, 13 BlnI, and 7 I-CeuI macrorestriction sites. Macrorestriction mapping was rapidly accomplished by a novel transposon-based procedure: analysis of modified minitransposon insertions served to align the overlapping macrorestriction fragments generated by three different enzymes (each sharing a common cleavage site within the insert), thus integrating the three different digestion patterns and ordering the fragments. The resulting map, generated from a total of 54 mini-Tn10insertions, was supplemented with auxanography and Southern analysis to indicate the positions of insertionally disrupted aminosynthetic genes and cloned virulence genes, respectively. Thus, it contains not only physical, macrorestriction landmarks but also the loci for eight housekeeping genes shared with strain K-12 and eight acknowledged urovirulence genes; the latter confirmed clustering of virulence genes at the large unique accessory chromosomal segments. The 115-kb J96 plasmid was resolved by pulsed-field gel electrophoresis inNotI digests. However, because the plasmid lacks restriction sites for the enzymes BlnI and I-CeuI, it was visualized in BlnI and I-CeuI digests only of derivatives carrying plasmid inserts artificially introducing these sites. Owing to an I-SceI site on the transposon, the plasmid could also be visualized and sized from plasmid insertion mutants after digestion with this enzyme. The insertional strains generated in construction of the integrated genomic map provide useful physical and genetic markers for further characterization of the J96 genome.

THE INDUCTION OF LAMBDA PROPHAGES BY CONTROLLED DESICCATION

1967 ◽  
Vol 13 (1) ◽  
pp. 33-43 ◽  
Author(s):  
S. J. Webb ◽  
M. D. Dumasia
Keyword(s):  
Escherichia Coli ◽  
Relative Humidity ◽  
Water Molecules ◽  
Compound I ◽  
Prophage Induction ◽  
E Coli ◽  
Escherichia Coli K12 ◽  
Number Of Cells

Cells of Escherichia coli K12 (λ +) and Escherichia coli M3 (λ59) were desiccated at various levels of relative humidity (R.H.). When the cells were cultured in an enriched medium and held at 55% R.H., induction of the prophage in 36% of E. coli K12 cells and 75% of E. coli M3 cells occurred. At 30% R.H. or 70% R.H., fewer inductions took place. The maximum number of cells in which prophage induction occurred was found 15 minutes after desiccation began with E. coli K12 and immediately after the cells were dried with E. coli M3. After the attainment of maximum levels of induction, plaque-forming ability was gradually destroyed, but the rate of destruction was dependent on the R.H. at which the cells were held. The plaque-forming ability of the free viruses and of cells in which prophage induction had occurred were destroyed by prolonged desiccation at different rates. Also, the loss of colony-forming ability of the cells was more rapid than the inactivation of plaque-forming ability of either induced prophages or the free viruses. The compound, i-inositol, prevented prophage induction by desiccation and also stopped the destruction of induced prophages within the cell.It is concluded that water molecules bound to the DNA hold the prophage to the host DNA and their removal results in induction.

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