scholarly journals Functional genes for cellobiose utilization in natural isolates of Escherichia coli.

1987 ◽  
Vol 169 (6) ◽  
pp. 2713-2717 ◽  
Author(s):  
B G Hall ◽  
W Faunce
Keyword(s):  
Escherichia Coli ◽  
Functional Genes ◽  
Natural Isolates

scholarly journals Production of 3-Nitrosoindole Derivatives by Escherichia coli during Anaerobic Growth

2009 ◽  
Vol 191 (17) ◽  
pp. 5369-5376 ◽  
Author(s):  
Young-Man Kwon ◽  
Bernard Weiss
Keyword(s):  
Escherichia Coli ◽  
Nitrous Acid ◽  
Anaerobic Growth ◽  
Functional Genes ◽  
Initial Reaction ◽  
Endonuclease V ◽  
Tryptophanase Activity ◽  
K 12 ◽  
Metabolic Reduction ◽  
Dna Repair Mutants

ABSTRACT When Escherichia coli K-12 is grown anaerobically in medium containing tryptophan and sodium nitrate, it produces red compounds. The reaction requires functional genes for trytophanase (tnaA), a tryptophan permease (tnaB), and a nitrate reductase (narG), as well as a natural drop in the pH of the culture. Mass spectrometry revealed that the purified chromophores had mass/charge ratios that closely match those for indole red, indoxyl red, and an indole trimer. These compounds are known products of chemical reactions between indole and nitrous acid. They are derived from an initial reaction of 3-nitrosoindole with indole. Apparently, nitrite that is produced from the metabolic reduction of nitrate is converted in the acid medium to nitrous acid, which leads to the nitrosation of the indole that is generated by tryptophanase. An nfi (endonuclease V) mutant and a recA mutant were selectively killed during the period of chromophore production, and a uvrA strain displayed reduced growth. These effects depended on the addition of nitrate to the medium and on tryptophanase activity in the cells. Unexpectedly, the killing of a tnaA + nfi mutant was not accompanied by marked increases in mutation frequencies for several traits tested. The vulnerability of three DNA repair mutants indicates that a nitrosoindole or a derivative of a nitrosoindole produces lethal DNA damage.

scholarly journals Variation in endogenous oxidative stress in Escherichia coli natural isolates during growth in urine

2012 ◽  
Vol 12 (1) ◽  
pp. 120 ◽  
Author(s):  
Cecile Aubron ◽  
Jeremy Glodt ◽  
Corine Matar ◽  
Olivier Huet ◽  
Didier Borderie ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Natural Isolates

scholarly journals Distribution of DNA insertion element IS5 in natural isolates of Escherichia coli.

1984 ◽  
Vol 81 (14) ◽  
pp. 4500-4504 ◽  
Author(s):  
L. Green ◽  
R. D. Miller ◽  
D. E. Dykhuizen ◽  
D. L. Hartl
Keyword(s):  
Escherichia Coli ◽  
Insertion Element ◽  
Natural Isolates ◽  
Dna Insertion

scholarly journals IS1397 Is Active for Transposition into the Chromosome of Escherichia coli K-12 and Inserts Specifically into Palindromic Units of Bacterial Interspersed Mosaic Elements

1999 ◽  
Vol 181 (22) ◽  
pp. 6929-6936 ◽  
Author(s):  
Jean-Marie Clément ◽  
Caroline Wilde ◽  
Sophie Bachellier ◽  
Patricia Lambert ◽  
Maurice Hofnung
Keyword(s):  
Escherichia Coli ◽  
Mobile Genetic Element ◽  
Basic Element ◽  
Genetic Element ◽  
Repeated Element ◽  
E Coli ◽  
Intergenic Regions ◽  
Natural Isolates ◽  
K 12

ABSTRACT We demonstrate that IS1397, a putative mobile genetic element discovered in natural isolates of Escherichia coli, is active for transposition into the chromosome of E. coliK-12 and inserts specifically into palindromic units, also called repetitive extragenic palindromes, the basic element of bacterial interspersed mosaic elements (BIMEs), which are found in intergenic regions of enterobacteria closely related to E. coli andSalmonella. We could not detect transposition onto a plasmid carrying BIMEs. This unprecedented specificity of insertion into a well-characterized chromosomal intergenic repeated element and its evolutionary implications are discussed.

Stationary-Phase Acid Resistance and Injury of Recent Bovine Escherichia coli O157 and non-O157 Biotype I Escherichia coli Isolates†

2004 ◽  
Vol 67 (3) ◽  
pp. 583-590 ◽  
Author(s):  
E. D. BERRY ◽  
G. A. BARKOCY-GALLAGHER ◽  
G. R. SIRAGUSA
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Acid Resistance ◽  
Low Ph ◽  
Acid Adaptation ◽  
E Coli ◽  
Log Reduction ◽  
Natural Isolates ◽  
Acidic Conditions ◽  
Ph Challenge

Stationary-phase acid resistance and the induction of acid resistance were assessed for recent bovine carcass isolates of Escherichia coli, including 39 serotype O157 strains and 20 non-O157 strains. When grown to stationary phase in the absence of glucose and without prior acid exposure, there was a range of responses to a pH challenge of 6 h at pH 2.5. However, populations of 53 of the 59 E. coli isolates examined were reduced by less than 2.00 log CFU/ml, and populations of 24 of these isolates were reduced by less than 1.00 log CFU/ml. In contrast, there was little variation in population reductions when the E. coli were grown with glucose and preadapted to acidic conditions. With few exceptions, acid adaptation improved survival to the acid challenge, with 57 of the 59 isolates exhibiting a log reduction of less than 0.50. Differences in acid resistance or the ability to adapt to acidic conditions between E. coli O157:H7 and non-O157 commensal E. coli were not observed. However, we did find that the E. coli O157 were disposed to greater acid injury after the low pH challenge than the non-O157 E. coli, both for cells that were and were not adapted to acidic conditions before the challenge. The enhancement of low pH survival after acid adaptation that was seen among these recent natural isolates of E. coli O157 further supports the idea that the previous environment of this pathogen should be a consideration when designing microbial safety strategies for foods preserved by low pH and acid.

Antibiotic resistance plasmids spread among natural isolates of Escherichia coli in spite of CRISPR elements

Microbiology ◽  
2012 ◽  
Vol 158 (12) ◽  
pp. 2997-3004 ◽  
Author(s):  
Marie Touchon ◽  
Sophie Charpentier ◽  
Dominique Pognard ◽  
Bertrand Picard ◽  
Guillaume Arlet ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Resistance Plasmids ◽  
Natural Isolates

Absence of Internalization of Escherichia coli O157:H7 into Germinating Tissue of Field-Grown Leafy Greens

2014 ◽  
Vol 77 (2) ◽  
pp. 189-196 ◽  
Author(s):  
MARILYN C. ERICKSON ◽  
CATHY C. WEBB ◽  
JUAN CARLOS DÍAZ-PÉREZ ◽  
LINDSEY E. DAVEY ◽  
ALISON S. PAYTON ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Contaminated Soil ◽  
Spinacia Oleracea ◽  
Field Studies ◽  
Growth Chamber ◽  
Escherichia Coli O157 ◽  
Apparent Lack ◽  
E Coli ◽  
Leafy Greens ◽  
Natural Isolates

Both growth chamber and field studies were conducted to investigate the potential for Escherichia coli O157:H7 to be internalized into leafy green tissue when seeds were germinated in contaminated soil. Internalized E. coli O157:H7 was detected by enrichment in both spinach (Spinacia oleracea L.) and lettuce (Lactuca sativa L.) seedlings when seeds were germinated within the growth chamber in autoclaved and nonautoclaved soil, respectively, contaminated with E. coli O157:H7 at 2.0 and 3.8 log CFU/g, respectively. Internalized E. coli O157:H7 populations could be detected by enumeration within leafy green tissues either by increasing the pathogen levels in the soil or by autoclaving the soil. Attempts to maximize the exposure of seed to E. coli O157:H7 by increasing the mobility of the microbe either through soil with a higher moisture content or through directly soaking the seeds in an E. coli O157:H7 inoculum did not increase the degree of internalization. Based on responses obtained in growth chamber studies, internalization of E. coli O157:H7 surrogates (natural isolates of Shiga toxin–negative E. coli O157:H7 or recombinant [stx- and eae-negative] outbreak strains of E. coli O157:H7) occurred to a slightly lesser degree than did internalization of the virulent outbreak strains of E. coli O157:H7. The apparent lack of internalized E. coli O157:H7 when spinach and lettuce were germinated from seed in contaminated soil (ca. 3 to 5 log CFU/g) in the field and the limited occurrence of surface contamination on the seedlings suggest that competition from indigenous soil bacteria and environmental stresses were greater in the field than in the growth chamber. On the rare occasion that soil contamination with E. coli O157:H7 exceeded 5 log CFU/g in a commercial field, this pathogen probably would not be internalized into germinating leafy greens and/or would not still be present at the time of harvest.

Sign in / Sign up

Export Citation Format

Share Document