scholarly journals Effect of Subinhibitory Concentrations of Antibiotics on Intrachromosomal Homologous Recombination in Escherichia coli

2009 ◽  
Vol 53 (8) ◽  
pp. 3411-3415 ◽  
Author(s):  
Elena López ◽  
Jesús Blázquez
Keyword(s):  
Escherichia Coli ◽  
Homologous Recombination ◽  
Dna Sequences ◽  
Sos Response ◽  
E Coli ◽  
Homologous Sequences ◽  
Sos Induction ◽  
Quinolone Antibiotics ◽  
Subinhibitory Concentrations ◽  
Sublethal Concentrations

ABSTRACT Subinhibitory concentrations of some antibiotics, such as fluoroquinolones, have been reported to stimulate mutation and, consequently, bacterial adaptation to different stresses, including antibiotic pressure. In Escherichia coli, this stimulation is mediated by alternative DNA polymerases induced via the SOS response. Sublethal concentrations of the fluoroquinolone ciprofloxacin have been shown to stimulate recombination between divergent sequences in E. coli. However, the effect of ciprofloxacin on recombination between homologous sequences and its SOS dependence have not been studied. Moreover, the possible effects of other antibiotics on homologous recombination remain untested. The aim of this work was to study the effects of sublethal concentrations of ciprofloxacin and 10 additional antibiotics, including different molecular families with different molecular targets, on the rate of homologous recombination of DNA in E. coli. The antibiotics tested were ciprofloxacin, ampicillin, ceftazidime, imipenem, chloramphenicol, tetracycline, gentamicin, rifampin (rifampicin), trimethoprim, fosfomycin, and colistin. Our results indicate that only ciprofloxacin consistently stimulates the intrachromosomal recombinogenic capability of homologous sequences in E. coli. The ciprofloxacin-based stimulation occurs at concentrations and times that apparently do not dramatically compromise the viability of the whole population, and it is dependent on RecA and partially dependent on SOS induction. One of the main findings of this work is that, apart from quinolone antibiotics, none of the most used antibiotics, including trimethoprim (a known inducer of the SOS response), has a clear side effect on homologous recombination in E. coli. In addition to the already described effects of some antibiotics on mutagenicity, DNA transfer, and genetic transformability in naturally competent species, the effect of increasing intrachromosomal recombination of homologous DNA sequences can be uniquely ascribed to fluoroquinolones, at least for E. coli.

Maize (Zea mays L.) DNA sequences homologous to the oncogenes myb, ras, and src

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 820-824 ◽  
Author(s):  
R. B. Zabulionis ◽  
B. G. Atkinson ◽  
J. D. Procunier ◽  
D. B. Walden
Keyword(s):  
Escherichia Coli ◽  
Zea Mays ◽  
Cell Division ◽  
Dna Sequences ◽  
Zea Mays L ◽  
Genomic Sequence ◽  
Evolutionary Conservation ◽  
Higher Plant ◽  
E Coli ◽  
Homologous Sequences

The presence of genes that may govern cell division and differentiation is being investigated in the agronomically important higher plant Zea mays. Heterologous animal oncogene probes (v-myb, v-fos, v-src, and v-Ki-ras) were hybridized to Southern-blotted endonuclease-restricted fragments of maize DNA under conditions that allowed up to 28% mismatch between the probe and genomic sequence. Human, yeast, and Escherichia coli endonuclease restricted DNA served as controls for the hybridization conditions used. The Southern blotted DNAs were hybridized with probes to ribosomal DNA and pBR322 to ensure that the observed hybridization signals were not due to spurious binding or contamination of the oncogene probes. Maize DNA sequences homologous to v-myb, v-src, and v-Ki-ras were detected. No maize sequences homologous to the v-fos probe were detected. The oncogene probes did not detect any homologous sequences in E. coli DNA and all the reported homologous bands in human and yeast DNA were observed. These results illustrate the evolutionary conservation of animal proto-oncogenes within the plant kingdom, and suggest that these sequences may play a role in the replication and differentiation of plant cells.Key words: oncogenes, v-myb, v-fos, v-src, v-Ki-ras, Zea mays.

scholarly journals Quorum Sensing Is a Global Regulatory Mechanism in Enterohemorrhagic Escherichia coli O157:H7

2001 ◽  
Vol 183 (17) ◽  
pp. 5187-5197 ◽  
Author(s):  
Vanessa Sperandio ◽  
Alfredo G. Torres ◽  
Jorge A. Girón ◽  
James B. Kaper
Keyword(s):  
Escherichia Coli ◽  
Quorum Sensing ◽  
Type Strain ◽  
Wild Type Strain ◽  
Regulatory Mechanism ◽  
Sos Response ◽  
Enterohemorrhagic Escherichia Coli ◽  
Trna Genes ◽  
Wild Type ◽  
E Coli

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is responsible for outbreaks of bloody diarrhea and hemolytic-uremic syndrome in many countries. EHEC virulence mechanisms include the production of Shiga toxins (Stx) and formation of attaching and effacing (AE) lesions on intestinal epithelial cells. We recently reported that genes involved in the formation of the AE lesion were regulated by quorum sensing through autoinducer-2, which is synthesized by the product of the luxS gene. In this study we hybridized an E. coli gene array with cDNA synthesized from RNA that was extracted from EHEC strain 86-24 and its isogenicluxS mutant. We observed that 404 genes were regulated by luxS at least fivefold, which comprises approximately 10% of the array genes; 235 of these genes were up-regulated and 169 were down-regulated in the wild-type strain compared to in theluxS mutant. Down-regulated genes included several involved in cell division, as well as ribosomal and tRNA genes. Consistent with this pattern of gene expression, theluxS mutant grows faster than the wild-type strain (generation times of 37.5 and 60 min, respectively, in Dulbecco modified Eagle medium). Up-regulated genes included several involved in the expression and assembly of flagella, motility, and chemotaxis. Using operon::lacZ fusions to class I, II, and III flagellar genes, we were able to confirm this transcriptional regulation. We also observed fewer flagella by Western blotting and electron microscopy and decreased motility halos in semisolid agar in the luxS mutant. The average swimming speeds for the wild-type strain and the luxS mutant are 12.5 and 6.6 μm/s, respectively. We also observed an increase in the production of Stx due to quorum sensing. Genes encoding Stx, which are transcribed along with λ-like phage genes, are induced by an SOS response, and genes involved in the SOS response were also regulated by quorum sensing. These results indicate that quorum sensing is a global regulatory mechanism for basic physiological functions of E. coli as well as for virulence factors.

Mutagenesis and More: umuDC and the Escherichia coli SOS Response

Genetics ◽  
1998 ◽  
Vol 148 (4) ◽  
pp. 1599-1610 ◽  
Author(s):  
Bradley T Smith ◽  
Graham C Walker
Keyword(s):  
Escherichia Coli ◽  
Dna Damage ◽  
Cellular Response ◽  
Sos Response ◽  
Posttranslational Regulation ◽  
E Coli ◽  
Sos Mutagenesis ◽  
Induced Mutagenesis ◽  
Mechanistic Basis ◽  
Increase Cell Survival

Abstract The cellular response to DNA damage that has been most extensively studied is the SOS response of Escherichia coli. Analyses of the SOS response have led to new insights into the transcriptional and posttranslational regulation of processes that increase cell survival after DNA damage as well as insights into DNA-damage-induced mutagenesis, i.e., SOS mutagenesis. SOS mutagenesis requires the recA and umuDC gene products and has as its mechanistic basis the alteration of DNA polymerase III such that it becomes capable of replicating DNA containing miscoding and noncoding lesions. Ongoing investigations of the mechanisms underlying SOS mutagenesis, as well as recent observations suggesting that the umuDC operon may have a role in the regulation of the E. coli cell cycle after DNA damage has occurred, are discussed.

scholarly journals Contributions of individual mechanisms to fluoroquinolone resistance in 36 Escherichia coli strains isolated from humans and animals.

1996 ◽  
Vol 40 (10) ◽  
pp. 2380-2386 ◽  
Author(s):  
M J Everett ◽  
Y F Jin ◽  
V Ricci ◽  
L J Piddock
Keyword(s):  
Escherichia Coli ◽  
Dna Sequences ◽  
Quinolone Resistance ◽  
Fluoroquinolone Resistance ◽  
Polymorphism Analysis ◽  
Single Mutation ◽  
Wild Type ◽  
Single Strand Conformational Polymorphism ◽  
E Coli ◽  
High Level

Twenty-eight human isolates of Escherichia coli from Argentina and Spain and eight veterinary isolates received from the Ministry of Agriculture Fisheries and Foods in the United Kingdom required 2 to > 128 micrograms of ciprofloxacin per ml for inhibition. Fragments of gyrA and parC encompassing the quinolone resistance-determining region were amplified by PCR, and the DNA sequences of the fragments were determined. All isolates contained a mutation in gyrA of a serine at position 83 (Ser83) to an Leu, and 26 isolates also contained a mutation of Asp87 to one of four amino acids: Asn (n = 14), Tyr (n = 6), Gly (n = 5), or His (n = 1). Twenty-four isolates contained a single mutation in parC, either a Ser80 to Ile (n = 17) or Arg (n = 2) or a Glu84 to Lys (n = 3). The role of a mutation in gyrB was investigated by introducing wild-type gyrB (pBP548) into all isolates; for three transformants MICs of ciprofloxacin were reduced; however, sequencing of PCR-derived fragments containing the gyrB quinolone resistance-determining region revealed no changes. The analogous region of parE was analyzed in 34 of 36 isolates by single-strand conformational polymorphism analysis and sequencing; however, no amino acid substitutions were discovered. The outer membrane protein and lipopolysaccharide profiles of all isolates were compared with those of reference strains, and the concentration of ciprofloxacin accumulated (with or without 100 microM carbony cyanide m-chlorophenylhydrazone [CCCP] was determined. Twenty-two isolates accumulated significantly lower concentrations of ciprofloxacin than the wild-type E. coli isolate; nine isolates accumulated less then half the concentration. The addition of CCCP increased the concentration of ciprofloxacin accumulated, and in all but one isolate the percent increase was greater than that in the control strains. The data indicate that high-level fluoroquinolone resistance in E. coli involves the acquisition of mutations at multiple loci.

scholarly journals A newly identified prophage-encoded gene, ymfM, causes SOS-inducible filamentation in Escherichia coli

2021 ◽  
Author(s):  
Shirin Ansari ◽  
James C. Walsh ◽  
Amy L. Bottomley ◽  
Iain G. Duggin ◽  
Catherine Burke ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Cell Division ◽  
Pathogenic Bacteria ◽  
Bacterial Resistance ◽  
Sos Response ◽  
E Coli ◽  
Ring Assembly ◽  
Multiple Alternative ◽  
Z Ring ◽  
Cell Division Inhibitor

Rod-shaped bacteria such as Escherichia coli can regulate cell division in response to stress, leading to filamentation, a process where cell growth and DNA replication continues in the absence of division, resulting in elongated cells. The classic example of stress is DNA damage which results in the activation of the SOS response. While the inhibition of cell division during SOS has traditionally been attributed to SulA in E. coli, a previous report suggests that the e14 prophage may also encode an SOS-inducible cell division inhibitor, previously named SfiC. However, the exact gene responsible for this division inhibition has remained unknown for over 35 years. A recent high-throughput over-expression screen in E. coli identified the e14 prophage gene, ymfM, as a potential cell division inhibitor. In this study, we show that the inducible expression of ymfM from a plasmid causes filamentation. We show that this expression of ymfM results in the inhibition of Z ring formation and is independent of the well characterised inhibitors of FtsZ ring assembly in E. coli, SulA, SlmA and MinC. We confirm that ymfM is the gene responsible for the SfiC phenotype as it contributes to the filamentation observed during the SOS response. This function is independent of SulA, highlighting that multiple alternative division inhibition pathways exist during the SOS response. Our data also highlight that our current understanding of cell division regulation during the SOS response is incomplete and raises many questions regarding how many inhibitors there actually are and their purpose for the survival of the organism. Importance: Filamentation is an important biological mechanism which aids in the survival, pathogenesis and antibiotic resistance of bacteria within different environments, including pathogenic bacteria such as uropathogenic Escherichia coli. Here we have identified a bacteriophage-encoded cell division inhibitor which contributes to the filamentation that occurs during the SOS response. Our work highlights that there are multiple pathways that inhibit cell division during stress. Identifying and characterising these pathways is a critical step in understanding survival tactics of bacteria which become important when combating the development of bacterial resistance to antibiotics and their pathogenicity.

Contribution of SOS Genes to H2O2-induced Apoptosis-like Death in Escherichia Coli

2021 ◽  
Author(s):  
Heesu Kim ◽  
Dong Gun Lee
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Treatment Strategies ◽  
Sos Response ◽  
Bacterial Dna ◽  
E Coli ◽  
New Treatment ◽  
Induced Apoptosis ◽  
And Function ◽  
The Relationship

Abstract Hydrogen peroxide (H2O2) is a debriding agent that damages the microbial structure and function by generating various reactive oxygen species (ROS). H2O2-produced hydroxyl radical (OH∙) also exert oxidative stress on microorganisms. The spread of antibiotic resistance in bacteria is a serious issue worldwide, and greater efforts are needed to identify and characterize novel antibacterial mechanisms to develop new treatment strategies. Therefore, this study aimed to clarify the relationship between H2O2 and Escherichia coli and to elucidate a novel antibacterial mechanism(s) of H2O2. Following H2O2 exposure, increased levels of 8-hydroxyldeoxyguanosine and malondialdehyde indicated that H2O2 accelerates oxidation of bacterial DNA and lipids in E. coli. As oxidative damage worsened, the SOS response was triggered. Cell division arrest and resulting filamentation were identified in cells, indicating that LexA was involved in DNA replication. It was also verified that RecA, a representative SOS gene, helps self-cleavage of LexA and acts as a bacterial caspase-like protein. Our findings also showed that dinF is essential to preserve E. coli from H2O2-induced ROS, and furthermore, demonstrated that H2O2-induced SOS response and SOS genes participate differently in guarding E. coli from oxidative stress. As an extreme SOS response is considered apoptosis-like death (ALD) in bacteria, additional experiments were performed to examine the characteristics of ALD. DNA fragmentation and membrane depolarization appeared in H2O2-treated cells, suggesting that H2O2 causes ALD in E. coli. In conclusion, our investigations revealed that ALD is a novel antibacterial mode of action(s) of H2O2 with important contributions from SOS genes.

scholarly journals C4b-binding protein exacerbates the host response to Escherichia coli

Blood ◽  
1991 ◽  
Vol 78 (2) ◽  
pp. 357-363 ◽  
Author(s):  
F Taylor ◽  
A Chang ◽  
G Ferrell ◽  
T Mather ◽  
R Catlett ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acute Phase ◽  
Protein C ◽  
Activated Protein C ◽  
Protein S ◽  
Organ Damage ◽  
Vascular Damage ◽  
E Coli ◽  
Infusion Group ◽  
Sublethal Concentrations

Abstract Activated protein C is a plasma anticoagulant. For activated protein C to function as an anticoagulant, it must form a complex with protein S. Protein S anticoagulant activity is neutralized by formation of a reversible complex with C4b binding protein (C4bBP). C4bBP is an acute- phase plasma protein. When C4bBP levels increase, mass action forces the level of free protein S to decrease, giving rise to an acquired functional protein S deficiency. It has been proposed that these elevated C4bBP levels and the resultant acquired deficiency of protein S that occurs in inflammation could contribute to a hypercoagulable state. An experimental model to test this hypothesis was suggested by our previous studies that demonstrated that inhibition of protein C activation rendered baboons hypercoagulable in response to sublethal Escherichia coli infusion (J Clin Invest 79:918, 1987). We have extended these studies to examine the effect of inhibition of protein S activity with C4bBP in the host (baboon) response to infusion of sublethal concentrations of E coli organisms. Five sets of animals were studied: (1) those challenged with sublethal concentrations of E coli alone (0.4 x 10(10)/kg); (2) those supplemented only with C4bBP (20 mg/kg); (3) those challenged with the same level of E coli but supplemented with C4bBP (20 mg/kg); (4) those challenged with sublethal E coli and supplemented with C4bBP (20 mg/kg) and sufficient protein S (2.3 mg/kg) to fill the protein S binding sites on C4bBP; and (5) those challenged with lethal concentrations of E coli. Sublethal E coli infusion (group 1 animals) caused only an acute-phase response with no consumption of fibrinogen, detectable organ damage, or detectable tumor necrosis factor (TNF) in the plasma. C4bBP infusion (group 2 animals) resulted in no significant physiologic changes, no detectable plasma TNF, and little change in fibrinogen level. The group 3 animals, receiving both sublethal E coli and C4bBP, exhibited rapid consumption of fibrinogen, systemic organ damage, and detectable circulating TNF ultimately leading to death. The overall response of this group was very similar to the response of the group 5 animals receiving an LD100 dose of E coli. The group 4 animals, which were treated exactly as above except that C4bBP was supplemented with a slight excess of protein S, responded essentially like those that received sublethal E coli alone. These studies suggest that the elevation of C4bBP during an inflammatory response can contribute to fibrinogen consumption and vascular damage. This vascular damage may be associated with enhanced elaboration of cytokines like TNF.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Constitutive soxR Mutations Contribute to Multiple-Antibiotic Resistance in Clinical Escherichia coli Isolates

2005 ◽  
Vol 49 (7) ◽  
pp. 2746-2752 ◽  
Author(s):  
Anastasia Koutsolioutsou ◽  
Samuel Peña-Llopis ◽  
Bruce Demple
Keyword(s):  
Nitric Oxide ◽  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Dna Sequences ◽  
Single Point ◽  
Constitutive Expression ◽  
Clinical Isolates ◽  
Multiple Antibiotic Resistance ◽  
E Coli ◽  
First Time

ABSTRACT The soxRS regulon of Escherichia coli and Salmonella enterica is induced by redox-cycling compounds or nitric oxide and provides resistance to superoxide-generating agents, macrophage-generated nitric oxide, antibiotics, and organic solvents. We have previously shown that constitutive expression of soxRS can contribute to quinolone resistance in clinically relevant S. enterica. In this work, we have carried out an analysis of the mechanism of constitutive soxS expression and its role in antibiotic resistance in E. coli clinical isolates. We show that constitutive soxS expression in three out of six strains was caused by single point mutations in the soxR gene. The mutant SoxR proteins contributed to the multiple-antibiotic resistance phenotypes of the clinical strains and were sufficient to confer multiple-antibiotic resistance in a fresh genetic background. In the other three clinical isolates, we observed, for the first time, that elevated soxS expression was not due to mutations in soxR. The mechanism of such increased soxS expression remains unclear. The same E. coli clinical isolates harbored polymorphic soxR and soxS DNA sequences, also seen for the first time.

scholarly journals Genomic Subtraction To Identify and Characterize Sequences of Shiga Toxin-Producing Escherichia coli O91:H21

2002 ◽  
Vol 68 (5) ◽  
pp. 2316-2325 ◽  
Author(s):  
Nathalie Pradel ◽  
Sabine Leroy-Setrin ◽  
Bernard Joly ◽  
Valérie Livrelli
Keyword(s):  
Escherichia Coli ◽  
Dna Sequences ◽  
Shiga Toxin ◽  
Shigella Flexneri ◽  
Virulence Determinants ◽  
E Coli ◽  
Virulence Plasmids ◽  
Subtraction Procedure ◽  
Uremic Syndrome ◽  
Genomic Subtraction

ABSTRACT To identify Shiga toxin-producing Escherichia coli genes associated with severe human disease, a genomic subtraction technique was used with hemolytic-uremic syndrome-associated O91:H21 strain CH014 and O6:H10 bovine strains. The method was adapted to the Shiga toxin-producing E. coli genome: three rounds of subtraction were used to isolate DNA fragments specific to strain CH014. The fragments were characterized by genetic support analysis, sequencing, and hybridization to the genome of a collection of Shiga toxin-producing E. coli strains. A total of 42 fragments were found, 19 of which correspond to previously identified unique DNA sequences in the enterohemorrhagic E. coli EDL933 reference strain, including 7 fragments corresponding to prophage sequences and others encoding candidate virulence factors, such a SepA homolog protein and a fimbrial usher protein. In addition, the subtraction procedure yielded plasmid-related sequences from Shigella flexneri and enteropathogenic and Shiga toxin-producing E. coli virulence plasmids. We found that lateral gene transfer is extensive in strain CH014, and we discuss the role of genomic mobile elements, especially bacteriophages, in the evolution and possible transfer of virulence determinants.

scholarly journals Binding and transcriptional activation of non-flagellar genes by the Escherichia coli flagellar master regulator FlhD2C2

Microbiology ◽  
2005 ◽  
Vol 151 (6) ◽  
pp. 1779-1788 ◽  
Author(s):  
Graham P. Stafford ◽  
Tomoo Ogi ◽  
Colin Hughes
Keyword(s):  
Escherichia Coli ◽  
Dna Sequences ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Class Ii ◽  
Promoter Regions ◽  
E Coli ◽  
Flagellar Genes

The gene hierarchy directing biogenesis of peritrichous flagella on the surface of Escherichia coli and other enterobacteria is controlled by the heterotetrameric master transcriptional regulator FlhD2C2. To assess the extent to which FlhD2C2 directly activates promoters of a wider regulon, a computational screen of the E. coli genome was used to search for gene-proximal DNA sequences similar to the 42–44 bp inverted repeat FlhD2C2 binding consensus. This identified the binding sequences upstream of all eight flagella class II operons, and also putative novel FlhD2C2 binding sites in the promoter regions of 39 non-flagellar genes. Nine representative non-flagellar promoter regions were all bound in vitro by active reconstituted FlhD2C2 over the K D range 38–356 nM, and of the nine corresponding chromosomal promoter–lacZ fusions, those of the four genes b1904, b2446, wzz fepE and gltI showed up to 50-fold dependence on FlhD2C2 in vivo. In comparison, four representative flagella class II promoters bound FlhD2C2 in the K D range 12–43 nM and were upregulated in vivo 30- to 990-fold. The FlhD2C2-binding sites of the four regulated non-flagellar genes overlap by 1 or 2 bp the predicted −35 motif of the FlhD2C2-activated σ 70 promoters, as is the case with FlhD2C2-dependent class II flagellar promoters. The data indicate a wider FlhD2C2 regulon, in which non-flagellar genes are bound and activated directly, albeit less strongly, by the same mechanism as that regulating the flagella gene hierarchy.

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