g. [4, 13–16]). This study utilizes an engineering approach, known as robustness analysis, which is used to analyze complex systems. Robustness analysis determines the stability of a system response to perturbations. Robust systems return similar or identical responses when perturbed

while non-robust systems return very different responses [17, 18]. Biofilm antibiotic tolerance is a product of complex cellular systems. The presented study examines the robustness of colony biofilm antibiotic tolerance to industrially and medically relevant perturbations including 1) nutrient environment 2) temperature 3) quorum sensing ability and 4) growth phase. To our knowledge, this is the first time robustness analysis has been applied to biofilm antibiotic tolerance. Antibiotic tolerance is at the heart of many practical challenges related to unwanted biofilms. Being able to predict biofilm antibiotic tolerance learn more as a function of culturing perturbations is essential for rationally designing and evaluating antimicrobial strategies. The presented results shed insight on the varying success rates of common

anti-fouling strategies like antibiotic impregnated coatings and provide a template for improved antimicrobial testing schemes. Results 1. Antibiotic tolerance in planktonic and biofilm cultures Biofilms often exhibit very different antibiotic tolerances than planktonic cultures [1–4]. To interpret the presented biofilm data in an appropriate context, the antibiotic tolerances Selleckchem Ku 0059436 of biofilm

cultures were compared to planktonic cultures. Antibiotics representing the aminoglycoside and beta-lactam classes were used as proxies for the diverse array of utilized agents. Kanamycin and ampicillin tolerances were determined for planktonic and Casein kinase 1 biofilm cultures grown in Luria-Bertani (LB) medium at 37°C. These antibiotics were highly effective against planktonic cultures reducing colony forming units (cfu’s)/ml by 6 to 9 orders of magnitude (Fig. 1a). The biofilm antibiotic tolerance results were varied. Kanamycin produced a 9 log10 reduction in cfu’s per biofilm while ampicillin resulted in only a one log10 reduction in cfu’s per biofilm (Fig 1b). Subsequent biofilm responses to culturing perturbations were compared to these base tolerance results (Fig. 1b). Just prior to antibiotic challenge, the biofilm cultures contained 9.3 log10 ± 0.1 cfu’s/biofilm while the planktonic cultures had 7.8 ± 0.2 log10 cfu’s/ml. Additional data illustrating differences in colony biofilm antibiotic susceptibility as compared to planktonic cultures can be found in Additional file 1, Figs. S1 and S5. Figure 1 Comparison of planktonic and biofilm antibiotic tolerance. Wild-type E. coli K-12 cultures were grown on LB only medium at 37°C. Cultures were grown for 6 hours before being transferred to fresh antibiotic treatment medium for 24 hours.

The inclusion

of MAP-specific click here genes in these deleted regions is an important observation as these genes could provide the basis for differentiating infected from vaccinated animals (DIVA). Indeed, the deleted region vGI-19 contains part of the 38 kb pathogenicity island described by Stratmann et al. (2004) [30] which contains genes encoding a number of antigens with diagnostic potential [31]. Both deleted regions vGI-19 and vGI-20 contain genes potentially involved in virulence and pathogenesis (Table  1) and their deletion could therefore have a profound effect on the virulence of these strains. In this study we demonstrated using a mouse model that both vaccine strains 2eUK2001 and IIUK2001 were attenuated with respect to a wild type MAP strain. In addition, vaccine strain MAPK Inhibitor Library cost IIUK2000 and IIUK2001 were found to contain a large 41 ORF tandem duplication (vGI-21) which includes copies

of benzoate and lipid metabolic pathways. Vaccine strain 2eUK2000 comes from the same stock as 2eUK2001 and was maintained at the VLA, UK for over 50 years on a mineral deficient medium (Watson Reid ‘A’ block) whilst vaccine strain IIUK2000 was not. We suggest that the vGI-21 duplication in vaccine strain IIUK2000 was selected by these differences in media and fixed into the genome to compensate in vitro for the deletion of lipid biosynthesis and carbon usage repertoires, removed by the vGI-20 deletion. The large deletion vGI-19 present in vaccine strain 316FNOR1960 was not present in any of the other 316 F strains including an early low passage lineage (316FCYP1966) and a more recent isolate (316 F2001)

shown to GPX6 be significantly attenuated in our virulence studies. Notably, part of vGI-19 is also present in the same gene order within the related MAH104 genome (GenBank reference CP000479). Together these suggest that any ancestral precursor and therefore the original 316 F strain would be unlikely to be missing vGI-19. We hypothesise that the vGI-19 deletion appeared in the 316FNOR1960 strain some point after its acquisition and transfer to Norway in 1960 from the VLA, UK. This strain is recorded as having been maintained, uniquely on Dubos medium with added pyruvate [15] and we hypothesise that this medium was at some point selective. This is supported by the vGI-19 deletion in this strain including gene homologues of glyoxylate enzymes associated with pyruvate metabolism [32]. This strain previously has been used successfully as a live vaccine suggesting that it is attenuated. The knockout of the glyoxylate shunt could significantly affect the strain’s ability to control anaerobic respiration [33] and intracellular persistence [34], which may indicate that attenuation in this strain may be related to this loss.

The aims of this study were: (a) to assess p53 nuclear accumulation and ERα expression in pure ductal hyperplasia and ductal hyperplasia co-existing with DCIS or IDC; (b) to explore if there is a differential

expression pattern of ERα and p53 nuclear accumulation between pure ductal hyperplasia and ductal hyperplasia co-existing with DCIS or IDC. Materials and methods Patients and tissues: 129 cases of pure ductal hyperplasia of breast, 86 cases of ductal hyperplasia Napabucasin purchase co-existing with DCIS (41 cases) and IDC (45 cases) were collected from surgical samples of women at the First Affiliated Hospital of China Medical University between 2005 and 2010. None of patients undergo chemotherapy, radiotherapy or adjuvant treatment before operation. Patients’ ages ranged from 21 to 82, with an average age of 43.8 years old. Each case was reviewed independently by 2 pathologists (Chui-feng Fan and

Min Song) with a subspecialty focus in breast pathology, and only those cases that both pathologists finally reached the unanimous diagnosis were used. In case of insufficient or unattainable material, original tissue blocks were reprocessed and new slides were created. The pathological types of breast ductal hyperplasia lesions have been classified according to WHO’s criteria which published by Tavassoli FA GSK1120212 et al [22]. All sections were reviewed for a comprehensive list of pathologic features, including margins (close margins were defined as tissue-free margins < 1 mm), the presence of

concomitant UDH, ADH, DCIS and IDC. The pathological types of breast ductal hyperplasia lesions were summarized in Table 1. The cases of breast ductal hyperplasia lesions include 79 cases of UDH and 136 cases of ADH (16 cases of ductal intraepithelial neoplasia 1A (DIN 1A) and 120 cases of ductal intraepithelial neoplasia 1B (DIN 1B)). The study was approved by the regional ethics Sitaxentan committee at China Medical University. Table 1 Breast ductal hyperplasia lesions of the different pathological types   Pure type With DCIS With IDC Total UDH 52 12 15 79 ADH 77 29 30 136    DIN 1A 1 9 6 16    DIN 1B 76 20 24 120 Total 129 41 45 215 Immunohistochemistry: Formalin-fixed and paraffin-embedded specimens were cut into 4 μm-thick sections, which were subsequently de-waxed and hydrated. Immunohistochemical staining for ERα (sc-542, Santa Cruz, 1:200) and p53 (sc-47698, Santa Cruz, 1:100) were performed using UltraSensitive™ S-P kits (Maixin-Bio; P.R. China) according to the manufacturer’s instructions and using the reagent supplied within the kit. For the negative control, phosphate-buffered saline (PBS) was used in place of the primary antibodies. We also adopted the German semi-quantitative scoring system in considering the staining intensity and area extent, which has been widely accepted and used in previous studies [23–25].

Johnson-Henry KC et al [10] reported that with probiotic pretreatment there was corresponding attenuation of the Enterohemorrhagic Escherichia coli (EHEC) O157:H7-induced drop in electrical resistance and the increase in barrier permeability assays. L. rhamnosus GG protected epithelial monolayers against EHEC-induced redistribution of the www.selleckchem.com/products/pexidartinib-plx3397.html claudin-1 and ZO-1 TJ proteins. Resta-Lenert S et al [20] hypothesized that probiotics and/or commensals could also reverse epithelial damage produced by cytokines.

They found that deleterious effects of TNF-α and IFN-γ on epithelial function were prevented by probiotic, and to a lesser extent, commensal pretreatment. A Janus kinase (JAK) inhibitor synergistically potentiated effects of Streptococcus thermophilus

(ST)/Lactobacillus acidophilus (LA) or Bacteroides thetaiotaomicron (BT) on TER and permeability, but p38, ERK1, 2, or PI3K inhibition did not. Finally, only probiotic-treated epithelial cells exposed to cytokines showed reduced activation of SOCS3 and STAT1,3. These data extended the spectrum of effects of such bacteria on intestinal epithelial function and may justify their use in inflammatory disorders. In addition, Seth AZD2281 molecular weight A et al [21] evaluated the effect of Lactobacillus rhamnosus GG-produced soluble proteins (p40 and p75) on the hydrogen peroxide-induced disruption of TJ and barrier function in Caco-2 cell monolayers. Pretreatment of cell monolayers with p40 or p75 attenuated the hydrogen peroxide-induced decrease in TER and increased in inulin permeability in a time- and dose-dependent manner. p40 and CYTH4 p75 also prevented hydrogen peroxide-induced redistribution of occludin, ZO-1, E-cadherin, and beta-catenin from the intercellular junctions and their dissociation from the detergent-insoluble fractions. Both p40 and p75 induced a rapid increased in the membrane translocation of PKCbetaI and PKCepsilon. The attenuation of hydrogen peroxide-induced inulin permeability and redistribution of TJ proteins by p40 and p75 was abrogated by Ro-32-0432,

a PKC inhibitor. p40 and p75 also rapidly increased the levels of phospho-ERK1/2 in the detergent-insoluble fractions. U0126 (a MAP kinase inhibitor) attenuated the p40- and p75-mediated reduction of hydrogen peroxide-induced TJ disruption and inulin permeability. These studies demonstrated that probiotic-secretory proteins protected the intestinal epithelial TJs and the barrier function from hydrogen peroxide-induced insult by a PKC- and MAP kinase-dependent mechanism. This study broadens our current understanding of how probiotics exert their beneficial effects and emphasizes the ability of L. plantarum (CGMCC 1258) to protect polarized epithelial cells against the effects of E. coli-induced changes in barrier function.

In our study, the expressional level of Annexin A1, A2, A3, A5 and A7 increased JAK/stat pathway compared with the normal liver tissue. Annexins consist of a conserved protein family. Annexin A2 is closely associated with cell division regulation and tumor growth, and is deregulated in many tumors[56, 57]. Two Annexin A2 molecules bind to the long chains of p11/S100A10 dimers through its N-terminals, form the isotetramer, regulating the reactions of Annexin A2 and membranes and actin in cortical areas, and the distribution of recirculating endosomes[58]. In addition, S100A10 and Annexin A2 form isodimers, prompting the invasion and metastasis

of the tumor by activating plasminogen[59]. In the present study, the expression level of S100a10, S100a11, S100a6, S100a8 and S100a9 increased from cirrhosis to metastatic process when compared with the normal liver. S100A8/A9 form the compounds that play a role in inducing apoptosis in tumor cells. S100A8/A9 at low concentrations prompts growth activity,

the phosphorylation of MAPK pathway and NF-κB is activated in cells after S100A8/A9 treatment. The majority of HCCs slowly unfold against a background of chronic hepatitis and cirrhosis, which can be considered this website as preneoplastic conditions of the liver. Chronic hepatitis is characterized by persistent inflammation, cytokine and oxidative stress-mediated hepatocyte death and active proliferation of residual hepatocytes to replace the lost parenchyma[1, 60]. During the process of hepatocarcinogenesis in rat models, chronic inflammation precedes cirrhosis. Epidemiology studies showed that chronic inflammation increased the risk of tumors, and the microenvironment of tumorigenesis resembles the reaction of inflammation to injury in many

ways[61]. In the tumor microenvironment, the chemotactic factors and receptors mediated angiogenesis, recruited cells, prompting cellular survival and proliferation. On the other hand, oxidative stress occurred in inflammatory processes. The inflammatory cells and tumor cells both produce free radicals and soluble factors such as arachidonic acid, cytokines and chemotactic factors, seubsequently producing reactive oxygen. All these factors strongly recruit the inflammatory cells to produce Non-specific serine/threonine protein kinase cytokines, which promotes a vicious cycle. The intermediate products of active oxygen oxidize DNA directly or interfere with DNA repair. These oxides activate protein, carbohydrate and lipids quickly, the derived products interfere with inter- and intracellular homeostasis, favoring DNA mutation. Thus, the chronic inflammation prompts the malignant transformation of cells[62]. Chronic inflammation also favors angiogenesis[63]. In the present study, many DEGs are related to inflammation reaction, immune reaction and stress.

Such a process seems to involve the whole thyroid gland. Since a constitutively active STAT3, associated to cytoplasmic

accumulation of p53, has been reported to represent a risk factor for tumor development [11], total thyroidectomy may be supported as an adequate therapeutic choice Vemurafenib in cases where such alterations are detected. References 1. Friguglietti CU, Lin CS, Kulcsar MA: Total thyroidectomy for benign thyroid diseases. Laryngoscope 2003, 113:1820–6.PubMedCrossRef 2. Wei WZ, Morris GP, Kong YC: Anti-tumor immunity and autoimmunity: a balancing act of regulatory T cells. Cancer Immunol Immunother 2004, 53:73–8.PubMedCrossRef 3. Muller-Newen G: The cytokine receptor gp130: faithfully promiscuous. SciSTKE 2003, 201:PE40. 4. Calo V, Migliavacca M, Bazan V, Macaluso M, Buscemi M, Gebbia N, Russo A: STAT proteins: from normal control of cellular events to tumorigenesis. J Cell Physiol 2003, 197:157–68.PubMedCrossRef 5. Lin J, Jin X, Rothman K, Lin HJ, Tang

H, Burke W: Modulation of signal transducer and activator of transcription 3 activities by p53 tumor suppressor in breast cancer cells. Cancer Res 2002, 62:376–80.PubMed 6. Leu C, Wong F, Chang C, Huang S, Hu C: Interleukin-6 acts as an antiapoptotic factor in human esophageal carcinoma cells through the activation of both STAT3 and mitogenactivated protein kinase pathways. Oncogene 2003, 22:7809–18.PubMedCrossRef 7. Lin J, Tang H, Jin X, Jia G, Hsieh JT: p53 regulates STAT3 phosphorylation and DNA binding activity in human prostate cancer cells expressing constitutively active STAT3. Oncogene 2002, 21:3082–8.PubMedCrossRef 8. Qu L, Huang S, Baltzis see more D, Rivas-Estilla AM, Pluquet O, Hatzglou M, Koumenis C, Taya Y, Yoshimura A, Koromilas AE: Endoplasmic reticulum stress induces Florfenicol p53 cytoplasmic localization and prevents p53-dependent apoptosis by a pathway involving glycogen synthase

kinase-3beta. Genes Dev 2004, 26:234–9. 9. Casey MB, Lohse CM, Lloyd RV: Distinction between papillary thyroid hyperplasia and papillary thyroid carcinoma by immunohistochemical staining for CK19, galectin-3 and HBME-1. Endocr Pathol 2003, 14:55–60.PubMedCrossRef 10. Royuela M, Ricote M, Parsons MS, Garcia-Tunon I, Paniagua R, de Miguel MP: Immunohistochemical analysis of the IL-6 family of cytokines and their receptors in benign, hyperplastic, and malignany human prosatate. J Pathol 2004, 202:41–49.PubMedCrossRef 11. Bosari S, Viale G, Bossi P, Maggioni M, Coggi G, Murray JJ, Lee AK: Cytoplasmic accumulation of p53 protein: an independent prognostic indicator in colorectal adenocarcinomas. J Natl Cancer Inst 1994, 86:681–7.PubMedCrossRef Competing interests The authors declare that they have no competing interests. Authors’ contributions GA performed thyroid surgery, participated in study design and coordination. LR participated to perform thyroid surgery, participated in the sequence alignment and drafted the manuscript.

difficile infection is invariably associated with the disruption of the normal intestinal microflora by the administration of broad spectrum antibiotics. Thus there is a pressing need to develop therapies that selectively target C. difficile while leaving the intestinal microflora intact. The C. difficile reference strain 630 encodes a single predicted sortase, CD630_27180, which has strong amino acid similarity with SrtB of S. aureus CP-690550 datasheet and B. anthracis

[24]. Sortase substrates frequently contribute toward pathogenesis via their involvement in attachment to specific tissues during infection [17,41–44], as well as the bacteria’s ability to evade the immune response of the host [32,36]. Sortases, although not essential for growth or viability of the organism, are often essential for virulence in Gram-positive organisms; inactivation of sortases reduces colonization in mice [8,13,44,45], and decreases adhesion and invasion in vitro [8,10,14,46,47]. Sortases and their substrates are considered promising targets

for the development of new anti-infective compounds [10,14,48]. Unusually for Gram-positive bacteria, C. difficile appears to possess a single sortase enzyme that is likely to be important for the viability of the pathogen as we have been unable to construct a C. difficile strain 630 SrtB defined mutant (unpublished data). Inhibiting the C. difficile sortase could prove to be a strategy to specifically target C. difficile. In this study, we cloned, expressed and characterized the sortase encoded by CD630_27180 learn more of C. difficile 630, a predicted class B sortase (SrtB). Sortase nomenclature is based on sequence similarity to the known classes of sortase, A-F [7]. Sortases of class B typically are involved in heme-iron uptake and tend to be expressed in operons with their substrates [17,18]. Genes encoding class A sortases are not found in proximity to their substrates, which consist of a variety of surface proteins with diverse biological functions. Several many exceptions to these rules have already

been described, notably a class B sortase that polymerizes pilin subunits in S. pyogenes [49], and a class E sortase from C. diphtheriae that serves a housekeeping function [50]. The potential C. difficile sortase substrates identified in this paper comprise a diverse range of surface proteins, suggesting that SrtB may serve as a housekeeping sortase in C. difficile, a function usually reserved for class A sortases. These potential sortase substrates in C. difficile strain 630 comprise of seven proteins, all containing an (S/P)PXTG motif, that are predicted to be surface localized and are conserved across C. difficile strains. Recently it was proposed that a C. difficile collagen binding protein, CbpA, may be sorted to the cell surface by sortase recognizing an NVQTG motif [30]. In this study, we developed a FRET-based assay to demonstrate that SrtB of C.

MZ performed all bioinformatic analysis of CRISPR/Cas system in G. vaginalis genomes. AZ participated in the design of the study and revised the manuscript. All authors read and approved the final manuscript.”
“Background The digestive tracts of living systems, from nematodes to humans, contain a zoo of microorganisms. Many of these microbiota fill a required role for the host. The microbiota in human gastrointestinal systems produce folate and vitamin K, break down excess sugars and fibers, and help activate certain medications [1, 2]. However, digestive MI-503 mw tracts also play host to various bacteria associated with pathophysiological states. Ulcerative colitis, diabetes mellitus,

and irritable bowel syndrome are just a few of the diseases influenced by intestinal microbiota [1]. Microorganisms of the intestinal tract have been shown to influence the aging process. Metchnikoff suggested that the longevity of Bulgarians was attributed to their consumption of lactic acid generating RXDX-106 order bacteria in yogurts [3]. Although the composition of the intestinal microbiome seems to be unique to each individual [4], there are common trends when the gut microbiome

of babies is compared across diverse cultures [5]. Some studies have shown certain age-related diseases can be prevented or ameliorated with the use of certain microorganisms [6]. Model organisms can be utilized as a first step in assessing the relationship between longevity and the gut microbiome. Altering gut microorganism composition can influence the aging process in model systems in a safe and effective manner [7, 8]. Mice fed diets supplemented with Lactobacillus as a probiotic not only showed no pathogenic response, but also lived longer than littermates on a standard diet [9]. C. elegans is routinely maintained on the standard lab E. coli strain OP50. Wild-type (N2) worms fed this diet live an average of two weeks [10], and recapitulate many of the aging-related changes observed in humans. Old worms show muscular disorganization, diminished those movement, and

accumulate the aging-related pigment lipofuscin [11, 12]. Worms fed OP50 show an accumulation of bacteria in the pharynx and gut as they age [13–15] and old nematodes appear constipated [14]. C. elegans fed diets of either Lactobacillus or Bifidobacterium were long-lived and more resistant to the enteropathogen Salmonella enterica as compared to worms fed the standard OP50 E. coli lab diet [16]. Feeding worms a diet of GD1 E. coli deficient in coenzyme Q (ubiquinone or Q) leads to an increased life span without a cost to fertility [17, 18]. Q is an essential lipid component of the electron transport chain and is required for respiration-dependent energy production. The life span increase of nematodes fed a GD1 Q-less E.

J Am Geriat Soc 50:897–905PubMed 84. Thelen DG, Muriuki M, James J, Schultz AB, Ashton-Miller JA, Alexander NB (2000) Muscle activities used by young and old adults when stepping to regain balance during a forward fall. J Electromyogr Kinesiol 10:93–101PubMed 85. Thelen DG, Wojcik LA, Schultz AB, Ashton-Miller JA, Alexander NB (1997) Age differences in using a rapid step to regain balance during a forward fall. J Gerontol Ser A Biol Sci Med Sci 52:M8–13 86. Wojcik LA, Thelen DG, Schultz AB, Ashton-Miller JA, Alexander NB (1999) Age and gender differences in single-step recovery from a forward fall. J Gerontol Ser A Biol Sci Med Sci 54:M44–50 87. Wojcik LA, https://www.selleckchem.com/products/r428.html Thelen DG, Schultz AB,

Ashton-Miller JA, Alexander NB (2001) Age and gender differences in peak lower extremity joint torques and ranges of motion used during single-step balance recovery from a forward fall. J Biomech 34:67–73PubMed 88. Visser M, Goodpaster BH, Kritchevsky SB, Newman AB, Nevitt M, Rubin SM, Simonsick EM, Harris TB (2005) Selleckchem PF-562271 Muscle mass, muscle strength, and muscle fat infiltration as predictors of incident mobility limitations

in well-functioning older persons. J Gerontol Ser A Biol Sci Med Sci 60:324–333 89. Lang TF, Cauley J, Tylavsky F, Bauer D, Cummings S, Harris TB (2009) Computed tomography measurements of thigh muscle cross-sectional area and attenuation coefficient predict hip fracture: The Health, Aging and Body Composition Study. J Bone Miner Res doi:10.​1359/​jbmr.​090807 90. Frontera WR, Meredith CN, O’Reilly KP, Knuttgen HG, Dichloromethane dehalogenase Evans WJ (1988) Strength conditioning in older men: skeletal muscle hypertrophy and improved function. J Appl Physiol 64:1038–1044PubMed 91. Charette SL, McEvoy L, Pyka G, Snow-Harter C, Guido D, Wiswell RA, Marcus R (1991) Muscle hypertrophy response to resistance training in older women. J Appl Physiol 70:1912–1916PubMed 92. Henwood TR, Taaffe DR (2008) Detraining and retraining in older adults following long-term muscle power or muscle strength specific training. J Gerontol

A Biol Sci Med Sci 63:751–758PubMed 93. Fiatarone MA, Marks EC, Ryan ND, Meredith CN, Lipsitz LA, Evans WJ (1990) High-intensity strength training in nonagenarians. Effects on skeletal muscle. JAMA 263:3029–3034PubMed 94. Fiatarone MA, O’Neill EF, Ryan ND, Clements KM, Solares GR, Nelson ME, Roberts SB, Kehayias JJ, Lipsitz LA, Evans WJ (1994) Exercise training and nutritional supplementation for physical frailty in very elderly people. N Engl J Med 330:1769–1775PubMed 95. Morley JE, Haren MT, Kim MJ, Kevorkian R, Perry HM 3rd (2005) Testosterone, aging and quality of life. J Endocrinol Invest 28:76–80PubMed 96. Borst SE (2004) Interventions for sarcopenia and muscle weakness in older people. Age Ageing 33:548–555PubMed 97.

However, in contrast to chloramphenicol that enhanced the bactericidal effect of H2O2 (Figure 8, left half, cross-hatched bar), the addition of ampicillin reduced the bactericidal activity of H2O2 for unknown reasons www.selleckchem.com/products/Romidepsin-FK228.html (Figure 8, left half, compare horizontally hatched bar to diagonally-hatched bar). This indicates that the synergistic effect of chloramphenicol on the bactericidal activity of H2O2 is not due to its bacteriostatic effect and suggests that protein synthesis is important for E. coli to resist the killing by H2O2. Figure 8 Chloramphenicol enhanced the bactericidal activity of H 2 O 2 . The wild type E. coli (WT) and the ΔarcA mutant E. coli (ΔarcA) were incubated in M9

minimal medium containing 1.5 mM H2O2 for 6 hours at 37°C. The survival of bacteria was determined by plating. Bacterial concentration following each treatment (open bars, no treatment; diagonally-hatched GS-1101 cell line bars, H2O2; vertically-hatched bars, 25 μg ml-1 of chloramphenicol; cross-hatched bars, H2O2 and 25 μg ml-1 of chloramphenicol; dotted line-hatched bars, 50 μg

ml-1 ampicillin and horizontally-hatched bars, H2O2 and 50 μg ml-1 ampicillin) was plotted on the graph. The horizontal dashed line indicates the starting concentration of bacteria. Similar assays were carried out with the ΔarcA mutant E. coli and the results were consistent with those of the wild type E. coli. While incubation with H2O2 alone reduced the concentration of the ΔarcA mutant E. coli by over 5log10 after 6 hours of incubation (Figure 8, right half, diagonally-hatched bar), the addition of chloramphenicol to the assay eliminated all E. coli (Figure 8). The synergistic effect of the bactericidal activity of H2O2 and chloramphenicol on the ΔarcA mutant E. coli is not because it is more susceptible to chloramphenicol (Figure 8, vertically-hatched bars). Similarly to that observed with wild type E. coli, ampicillin reduced the bactericidal activity Tyrosine-protein kinase BLK of H2O2, and the ΔarcA mutant E. coli survived better

in the presence of both ampicillin and H2O2 than H2O2 alone (1.7 × 105 CFU/ml vs. 1.0 × 102 CFU/ml) (Figure 8). Discussion Although the ArcAB system has been extensively investigated for its role as the global control system of E. coli in anaerobic growth, its role, if any, in aerobic growth is much less understood. We have previously reported that ArcA is necessary for the pathogenic bacterium Salmonella enterica to resist reactive oxygen and nitrogen species under aerobic conditions [38]. In this report, we used E. coli as our model to further explore the role of both ArcA and ArcB in ROS resistance, and to investigate the mechanism of ROS resistance mediated by the ArcAB two-component system. Here we demonstrate that deletion mutants of ArcA and ArcB were more susceptible to H2O2, suggesting that both ArcA and ArcB were necessary for E. coli to resist the stress caused by H2O2 (Figure 1), and that their functions were not limited to anaerobic growth of bacteria.