scholarly journals Identification, expression, and DNA sequence of the GDP-mannose biosynthesis genes encoded by the O7 rfb gene cluster of strain VW187 (Escherichia coli O7:K1).

1993 ◽  
Vol 175 (1) ◽  
pp. 148-158 ◽  
Author(s):  
C L Marolda ◽  
M A Valvano
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Dna Sequence

scholarly journals Association of Nucleotide Polymorphisms within the O-Antigen Gene Cluster of Escherichia coli O26, O45, O103, O111, O121, and O145 with Serogroups and Genetic Subtypes

2012 ◽  
Vol 78 (18) ◽  
pp. 6689-6703 ◽  
Author(s):  
Keri N. Norman ◽  
Nancy A. Strockbine ◽  
James L. Bono
Keyword(s):  
Escherichia Coli ◽  
Gene Cluster ◽  
Dna Sequence ◽  
Shiga Toxin ◽  
Severe Disease ◽  
The United States ◽  
Effective Control ◽  
Nucleotide Polymorphisms ◽  
Antigen Gene ◽  
O Antigen

ABSTRACTShiga toxin-producingEscherichia coli(STEC) strains are important food-borne pathogens capable of causing hemolytic-uremic syndrome. STEC O157:H7 strains cause the majority of severe disease in the United States; however, there is a growing concern for the amount and severity of illness attributable to non-O157 STEC. Recently, the Food Safety and Inspection Service (FSIS) published the intent to regulate the presence of STEC belonging to serogroups O26, O45, O103, O111, O121, and O145 in nonintact beef products. To ensure the effective control of these bacteria, sensitive and specific tests for their detection will be needed. In this study, we identified single nucleotide polymorphisms (SNPs) in the O-antigen gene cluster that could be used to detect STEC strains of the above-described serogroups. Using comparative DNA sequence analysis, we identified 22 potentially informative SNPs among 164 STEC and non-STEC strains of the above-described serogroups and designed matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF) assays to test the STEC allele frequencies in an independent panel of bacterial strains. We found at least one SNP that was specific to each serogroup and also differentiated between STEC and non-STEC strains. Differences in the DNA sequence of the O-antigen gene cluster corresponded well with differences in the virulence gene profiles and provided evidence of different lineages for STEC and non-STEC strains. The SNPs discovered in this study can be used to develop tests that will not only accurately identify O26, O45, O103, O111, O121, and O145 strains but also predict whether strains detected in the above-described serogroups contain Shiga toxin-encoding genes.

DNA sequence of theEscherichia coliO103 O antigen gene cluster and detection of enterohemorrhagicE. coliO103 by PCR amplification of thewzxandwzygenes

2005 ◽  
Vol 51 (6) ◽  
pp. 515-522 ◽  
Author(s):  
Pina M Fratamico ◽  
Chitrita DebRoy ◽  
Terence P Strobaugh, Jr. ◽  
Chin-Yi Chen
Keyword(s):  
Escherichia Coli ◽  
Real Time ◽  
Gene Cluster ◽  
Dna Sequence ◽  
Shiga Toxin ◽  
E Coli ◽  
Antigen Gene ◽  
O Antigen ◽  
Pcr Assays ◽  
Pcr Targeting

Escherichia coli serogroup O103 has been associated with gastrointestinal illness and hemolytic uremic syndrome. To develop PCR-based methods for detection and identification of this serogroup, the DNA sequence of the 12 033-bp region containing the O antigen gene cluster of Escherichia coli O103 was determined. Of the 12 open reading frames identified, the E. coli O103 wzx (O antigen flippase) and wzy (O antigen polymerase) genes were selected as targets for development of both conventional and real-time PCR assays specific for this serogroup. In addition, a multiplex PCR targeting the Shiga toxin (Stx) 1 (stx1), Shiga toxin 2 (stx2), wzx, and wzy genes was developed to differentiate Stx-producing E. coli O103 from non-toxigenic strains. The PCR assays can be employed to identify E. coli serogroup O103, replacing antigen-based serotyping, and to potentially detect the organism in food, fecal, or environmental samples.Key words: real-time polymerase chain reaction, E. coli typing, E. coli O103, O antigen DNA sequence.

scholarly journals Further tests of a recombination model in which chi removes the RecD subunit from the RecBCD enzyme of Escherichia coli.

Genetics ◽  
1990 ◽  
Vol 126 (3) ◽  
pp. 519-533 ◽  
Author(s):  
F W Stahl ◽  
L C Thomason ◽  
I Siddiqi ◽  
M M Stahl
Keyword(s):  
Escherichia Coli ◽  
Dna Sequence ◽  
Dna Packaging ◽  
Lambda Phage ◽  
Recombination Model ◽  
Phage Types ◽  
Point Of Entry ◽  
Reciprocal Recombination ◽  
Recbcd Enzyme ◽  
Lambda Dna

Abstract When one of two infecting lambda phage types in a replication-blocked cross is chi + and DNA packaging is divorced from the RecBCD-chi interaction, complementary chi-stimulated recombinants are recovered equally in mass lysates only if the chi + parent is in excess in the infecting parental mixture. Otherwise, the chi 0 recombinant is recovered in excess. This observation implies that, along with the chi 0 chromosome, two chi + parent chromosomes are involved in the formation of each chi + recombinant. The trimolecular nature of chi +-stimulated recombination is manifest in recombination between lambda and a plasmid. When lambda recombines with a plasmid via the RecBCD pathway, the resulting chromosome has an enhanced probability of undergoing lambda x lambda recombination in the interval into which the plasmid was incorporated. These two observations support a model in which DNA is degraded by Exo V from cos, the sequence that determines the end of packaged lambda DNA and acts as point of entry for RecBCD enzyme, to chi, the DNA sequence that stimulates the RecBCD enzyme to effect recombination. The model supposes that chi acts by ejecting the RecD subunit from the RecBCD enzyme with two consequences. (1) ExoV activity is blocked leaving a highly recombinagenic, frayed duplex end near chi, and (2) as the enzyme stripped of the RecD subunit travels beyond chi it is competent to catalyze reciprocal recombination.

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