The excision of thymine dimers from DNA, filament formation and sensitivity to ultraviolet light in Escherichia coli K-12

Howard-Flanders, Paul; Simson, Eva; Theriot, Lee

doi:10.1016/0027-5107(64)90002-8

Cited by 93 publications

(92 citation statements)

References 15 publications

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“…This fact increases the importance of the findings described in this work. Although several cytotoxic properties have been related to SnCl2, humans may be exposed to stannous ions in several situations (Howard-Flanders et al, 1964;De Mattos et al, 2000). The results in Figure 1 reinforce the fact that SnCl2 exerted a lesive action on the survival of the culture of E. coli AB1157 in accordance with what had been previously reported by other authors Dantas et al,1996;Reiniger et al, 1999;Melo et al, 2001;Bernardo et al, 2002;Soares et al, 2004).…”

Section: Bacterial Survivalsupporting

confidence: 87%

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Biological effects of an aqueous extract of Salix alba on the survival of Escherichia coli AB1157 cultures submitted to the action of stannous chloride

Souza

Manoel

et al. 2009

Biol. Res.

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Stannous chloride (SnCl2) is used in nuclear medicine as a reducing agent to obtain technetium-99m-radiopharmaceuticals. It have been reported that natural products might reduce the genotoxic and cytotoxic effects related to SnCl2. This work evaluated the biological effects of an aqueous extract of Salix alba on the survival of Escherichia coli (E. coli) AB1157 (wild type) cultures submitted to the action of SnCl2. E. coli AB1157 cultures (exponential growth phase) were collected by centrifugation, washed and resuspended in 0.9%NaCl. Samples were incubated in water bath shaker with: (a) SnCl2 (25μg/ml), (b)Salix alba extract(11.6mg/ml) and (c)SnCl2(25μg/ml) + Salix alba extract (11.6mg/ml). Incubation with 0.9% NaCl was also carried out (control). At 60 min intervals, aliquots were withdrawn, diluted, spread onto Petri dishes with solid LB medium and incubated overnight. The colonies formed were counted and the survival fractions calculated. The extract was not able to protect the E. coli cultures against the lesive action of SnCl2. The extract also did not interfere with the survival of the cultures. It suggested that the substances present in the Salix alba aqueous extract did not interfere strongly with cellular metabolism and did not alter the survival fractions of E. coli AB1157. It is speculated that this extract cannot interfere with the generation of free radicals, the possible main agent responsible for SnCl2 lesive action.

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Section: Bacterial Survivalsupporting

confidence: 87%

“…The cells were collected by centrifugation, washed twice in 0.9% NaCl and resuspended in the same solution, as previously reported (Howard-Flanders et al, 1964;Blunden and Wallace, 2003).…”

Section: Bacterial Survivalmentioning

confidence: 99%

Biological effects of an aqueous extract of Salix alba on the survival of Escherichia coli AB1157 cultures submitted to the action of stannous chloride

Souza

Manoel

et al. 2009

Biol. Res.

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“…Homologs exist ubiquitously in nature, however they localize to the cytosol in prokaryotes and to the mitochondrial matrix in eukaryotes (8,15,16 (11,(18)(19)(20)(21)(22)(23).…”

Section: Introductionmentioning

confidence: 99%

“…In fact the E. coli and S. Typhimurium Lon proteases differ in only 3 amino acids, none of which occur within the functional domains of the enzyme, indicating the two may function comparably. This is supported by the fact that Lon-deficient E. coli and S. Typhimurium are indistinguishable in their increased sensitivity to UV light and other DNA damaging agents, as well as their decreased ability to degrade abnormal proteins (11,(18)(19)(20)(21)(22)(23).…”

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confidence: 98%

Identification of the Proteasome Inhibitor MG262 as a Potent ATP-Dependent Inhibitor of the Salmonella enterica serovar Typhimurium Lon Protease

2006

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Lon is a homo-oligomeric ATP-dependent serine protease which functions in the degradation of damaged and certain regulatory proteins. The importance of Lon activity in bacterial pathogenicity has led to its emergence as a target in the development of novel antibiotics. As no potent inhibitors of Lon activity have been reported to date, we sought to identify an inhibitor which could serve as a lead compound in the development of a potent Lon-specific inhibitor. To determine whether a nucleotide-or peptide-based inhibitor would be more effective, we evaluated the steady-state kinetic parameters associated with both ATP and peptide hydrolysis by human and Salmonella enterica serovar Typhimurium Lon. Although the ATP hydrolysis activities of both homologs are kinetically indistinguishable, they display marked differences in peptide substrate specificity. This suggests that a peptide-based inhibitor could be developed which would target bacterial Lon, thereby decreasing side-effects due to cross-reactivity with human Lon. Using Salmonella enterica serovar Typhimurium Lon as a model, we evaluated the IC 50 values of a series of commercially available peptide-based inhibitors. Those inhibitors which behave as transition state analogs were the most useful in inhibiting Lon activity. The peptidyl boronate, MG262, was the most potent inhibitor tested (IC 50 = 122 ± 9 nM) and required binding, but not hydrolysis of ATP to initiate inhibition. We hope to use MG262 as a lead compound in the development of future Lon specific inhibitors.The number of pathogenic, antibiotic resistant bacteria increases each year, however the development of new antibiotics to treat them lags behind (1). Recent studies aimed at identifying proteins necessary for virulence have implicated the importance of Lon protease (2,3). Pathogenic Salmonella enterica are responsible for causing a range of human diseases from mild gastroenteritis (serovar Typhimurium and serovar Enteritidis) to typhoid fever (serovar Typhi). It has been demonstrated that Salmonella enteria serovar Typhimurium (S. Typhimurium) Lon protease activity is required for systemic infection in mice, a common study model for S. Typhi infection in humans (3). In fact, Lon-deficient S. Typhimurium, when administered as an oral vaccine to mice, conferred subsequent protection against infection by virulent S. Typhimurium (4). Taken together, these studies highlight Lon as an important target in the development of novel therapeutic agents.Lon, also known as the protease La, is a homo-oligomeric ATP-dependent serine protease, which functions in the degradation of damaged and certain short-lived regulatory proteins (5)(6)(7)(8)(9)(10)(11)(12)(13)(14). Homologs exist ubiquitously in nature, however they localize to the cytosol in prokaryotes and to the mitochondrial matrix in eukaryotes (8,15,16 (11,(18)(19)(20)(21)(22)(23).Lon protease is a member of the AAA + superfamily (ATPases Associated with different cellular Activities) along with other ATP-dependent proteases such as ClpXP, H...

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“…Quantification of prophage induction by mitomycin C. Mitomycin C causes cross-links of double-stranded DNA, activates an SOS response, and induces cell filamentation and phage production (22,23). Exposure of E. coli O104:H4 Δstx 2 ::gfp:: amp r to mitomycin C for 2 and 3 h induced gfp expression in 17 and 56% of cells of the population, respectively (Fig.…”

Section: Resultsmentioning

confidence: 99%

Induction of Shiga Toxin-Encoding Prophage by Abiotic Environmental Stress in Food

Fang

Mercer

McMullen

et al. 2017

Appl Environ Microbiol

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The prophage-encoded Shiga toxin is a major virulence factor in Stxproducing Escherichia coli (STEC). Toxin production and phage production are linked and occur after induction of the RecA-dependent SOS response. However, foodrelated stress and Stx-prophage induction have not been studied at the single-cell level. This study investigated the effects of abiotic environmental stress on stx expression by single-cell quantification of gene expression in STEC O104:H4 Δstx2::gfp:: amp r . In addition, the effect of stress on production of phage particles was determined. The lethality of stressors, including heat, HCl, lactic acid, hydrogen peroxide, and high hydrostatic pressure, was selected to reduce cell counts by 1 to 2 log CFU/ml. The integrity of the bacterial membrane after exposure to stress was measured by propidium iodide (PI). The fluorescent signals of green fluorescent protein (GFP) and PI were quantified by flow cytometry. The mechanism of prophage induction by stress was evaluated by relative gene expression of recA and cell morphology. Acid (pH Ͻ 3.5) and H 2 O 2 (2.5 mM) induced the expression of stx 2 in about 18% and 3% of the population, respectively. The mechanism of prophage induction by acid differs from that of induction by H 2 O 2 . H 2 O 2 induction but not acid induction corresponded to production of infectious phage particles, upregulation of recA, and cell filamentation. Pressure (200 MPa) or heat did not induce the Stx2-encoding prophage (Stx2-prophage). Overall, the quantification method developed in this study allowed investigation of prophage induction and physiological properties at the single-cell level. H 2 O 2 and acids mediate different pathways to induce Stx2-prophage.IMPORTANCE Induction of the Stx-prophage in STEC results in production of phage particles and Stx and thus relates to virulence as well as the transduction of virulence genes. This study developed a method for a detection of the induction of Stxprophages at the single-cell level; membrane permeability and an indication of SOS response to environmental stress were additionally assessed. H 2 O 2 and mitomycin C induced expression of the prophage and activated a SOS response. In contrast, HCl and lactic acid induced the Stx-prophage but not the SOS response. The lifestyle of STEC exposes the organism to intestinal and extraintestinal environments that impose oxidative and acid stress. A more thorough understanding of the influence of food processing-related stressors on Stx-prophage expression thus facilitates control of STEC in food systems by minimizing prophage induction during food production and storage.KEYWORDS single-cell detection, E. coli O104:H4, prophage induction, environmental stress, RecA-independent SOS response, membrane permeability, STEC, Shiga toxin, Shiga toxin-producing E. coli S higa toxin-producing Escherichia coli (STEC) causes the life-threatening hemolyticuremic syndrome (HUS), which is associated with acute renal failure and significant mortality (1, 2). Shiga toxins (Stx) include St...

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The excision of thymine dimers from DNA, filament formation and sensitivity to ultraviolet light in Escherichia coli K-12

Cited by 93 publications

References 15 publications

Biological effects of an aqueous extract of Salix alba on the survival of Escherichia coli AB1157 cultures submitted to the action of stannous chloride

Biological effects of an aqueous extract of Salix alba on the survival of Escherichia coli AB1157 cultures submitted to the action of stannous chloride

Identification of the Proteasome Inhibitor MG262 as a Potent ATP-Dependent Inhibitor of the Salmonella enterica serovar Typhimurium Lon Protease

Induction of Shiga Toxin-Encoding Prophage by Abiotic Environmental Stress in Food

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