scholarly journals Bile salts and ferric iron-induced PMRAB dependent resistance to camps in EHEC O157:H7

2021 ◽  
Author(s):  
Aju-sue Francis
Keyword(s):  
Induced Resistance ◽  
Bile Salts ◽  
Ferric Iron ◽  
Polymyxin B ◽  
Two Component System ◽  
Cationic Antimicrobial Peptide ◽  
Resistance Phenotype ◽  
Enterohaemorrhagic Escherichia Coli ◽  
Sense And Respond ◽  
Dose Dependent

Enterohaemorrhagic Escherichia coli O157:H7 (EHEC) colonization of the gastrointestinal tract is critically dependent on its ability to sense and respond to the external environment. This research aims to evaluate the contribution of bile salts- and ferric iron-induced resistance in EHEC to cationic antimicrobial peptide (CAMP) and the roles of pmrAB and am operon in these events. Results showed that EHEC, treatment with either bile salts or ferric iron induced a dose-dependent resistance to Polymyxin B. This resistance phenotype was lost in each of the pmrA and pmrB mutants. PMB resistance in EHEC was also dependent on the concentration of magnesium and on pH, suggesting the involvement of another two component system, PhoPQ. Mutagenesis of the iron-binding site of PmrB abrogated the induced resistance phenotype. The results of this study provide novel insights critical for our understanding of the molecular basis of pathogenesis and may provide new insights toward prevention strategies.

scholarly journals Bile salts and ferric iron-induced PMRAB dependent resistance to camps in EHEC O157:H7

2021 ◽  
Author(s):  
Aju-sue Francis
Keyword(s):  
Induced Resistance ◽  
Bile Salts ◽  
Ferric Iron ◽  
Polymyxin B ◽  
Two Component System ◽  
Cationic Antimicrobial Peptide ◽  
Resistance Phenotype ◽  
Enterohaemorrhagic Escherichia Coli ◽  
Sense And Respond ◽  
Dose Dependent

Enterohaemorrhagic Escherichia coli O157:H7 (EHEC) colonization of the gastrointestinal tract is critically dependent on its ability to sense and respond to the external environment. This research aims to evaluate the contribution of bile salts- and ferric iron-induced resistance in EHEC to cationic antimicrobial peptide (CAMP) and the roles of pmrAB and am operon in these events. Results showed that EHEC, treatment with either bile salts or ferric iron induced a dose-dependent resistance to Polymyxin B. This resistance phenotype was lost in each of the pmrA and pmrB mutants. PMB resistance in EHEC was also dependent on the concentration of magnesium and on pH, suggesting the involvement of another two component system, PhoPQ. Mutagenesis of the iron-binding site of PmrB abrogated the induced resistance phenotype. The results of this study provide novel insights critical for our understanding of the molecular basis of pathogenesis and may provide new insights toward prevention strategies.

scholarly journals Vibrio cholerae LeuO Links the ToxR Regulon to Expression of Lipid A Remodeling Genes

2016 ◽  
Vol 84 (11) ◽  
pp. 3161-3171 ◽  
Author(s):  
X. Renee Bina ◽  
Mondraya F. Howard ◽  
Vanessa M. Ante ◽  
James E. Bina
Keyword(s):  
Transcription Factor ◽  
Vibrio Cholerae ◽  
Bile Salts ◽  
Lipid A ◽  
Diarrheal Disease ◽  
Regulatory System ◽  
Polymyxin B ◽  
Environmental Cues ◽  
Cationic Antimicrobial Peptide ◽  
Content Type

Vibrio choleraeis an intestinal pathogen that causes the diarrheal disease cholera. Colonization of the intestine depends upon the expression of genes that allowV. choleraeto overcome host barriers, including low pH, bile acids, and the innate immune system. ToxR is a major contributor to this process. ToxR is a membrane-spanning transcription factor that coordinates gene expression in response to environmental cues. In previous work we showed that ToxR upregulatedleuOexpression in response to bile salts. LeuO is a LysR family transcription factor that contributes to acid tolerance, bile resistance, and biofilm formation inV. cholerae. Here, we investigated the function of ToxR and LeuO in cationic antimicrobial peptide (CAMP) resistance. We report that ToxR and LeuO contribute to CAMP resistance by regulatingcarRStranscription. CarRS is a two-component regulatory system that positively regulatesalmEFGexpression. AlmEFG confers CAMP resistance by glycinylation of lipid A. We found that the expression ofcarRSandalmEFGand the polymyxin B MIC increased in mutants lackingtoxRSorleuO. Conversely,leuOoverexpression decreased the polymyxin B MIC. Furthermore, we found that LeuO directly bound to thecarRSpromoter and that ToxR-dependent activation ofleuOtranscription regulatedcarRStranscription in response to bile salts. Our results suggest that LeuO functions downstream of ToxR to modulatecarRSexpression in response to environmental cues. This study extends the functional role of ToxR and LeuO in environmental adaptation to include cell surface remodeling and CAMP resistance.

scholarly journals New Aspects of RpoE in Uropathogenic Proteus mirabilis

2014 ◽  
Vol 83 (3) ◽  
pp. 966-977 ◽  
Author(s):  
Ming-Che Liu ◽  
Kuan-Ting Kuo ◽  
Hsiung-Fei Chien ◽  
Yi-Lin Tsai ◽  
Shwu-Jen Liaw
Keyword(s):  
Urinary Tract ◽  
Virulence Factors ◽  
Stress Responses ◽  
Proteus Mirabilis ◽  
Immune Cell ◽  
Polymyxin B ◽  
Urothelial Cells ◽  
Cationic Antimicrobial Peptide ◽  
Content Type ◽  
Tract Infections

Proteus mirabilisis a common human pathogen causing recurrent or persistent urinary tract infections (UTIs). The underlying mechanisms forP. mirabilisto establish UTIs are not fully elucidated. In this study, we showed that loss of the sigma factor E (RpoE), mediating extracytoplasmic stress responses, decreased fimbria expression, survival in macrophages, cell invasion, and colonization in mice but increased the interleukin-8 (IL-8) expression of urothelial cells and swarming motility. This is the first study to demonstrate that RpoE modulated expression of MR/P fimbriae by regulatingmrpI, a gene encoding a recombinase controlling the orientation of MR/P fimbria promoter. By real-time reverse transcription-PCR, we found that the IL-8 mRNA amount of urothelial cells was induced significantly by lipopolysaccharides extracted fromrpoEmutant but not from the wild type. These RpoE-associated virulence factors should be coordinately expressed to enhance the fitness ofP. mirabilisin the host, including the avoidance of immune attacks. Accordingly,rpoEmutant-infected mice displayed more immune cell infiltration in bladders and kidneys during early stages of infection, and therpoEmutant had a dramatically impaired ability of colonization. Moreover, it is noteworthy that urea (the major component in urine) and polymyxin B (a cationic antimicrobial peptide) can induce expression ofrpoEby the reporter assay, suggesting that RpoE might be activated in the urinary tract. Altogether, our results indicate that RpoE is important in sensing environmental cues of the urinary tract and subsequently triggering the expression of virulence factors, which are associated with the fitness ofP. mirabilis, to build up a UTI.

scholarly journals Intra- and Interspecies Signaling betweenStreptococcus salivarius and Streptococcus pyogenes Mediated by SalA and SalA1 Lantibiotic Peptides

2001 ◽  
Vol 183 (13) ◽  
pp. 3931-3938 ◽  
Author(s):  
M. Upton ◽  
J. R. Tagg ◽  
P. Wescombe ◽  
H. F. Jenkinson
Keyword(s):  
Streptococcus Pyogenes ◽  
Response Regulator ◽  
Genetic Locus ◽  
Two Component System ◽  
Peptide Modification ◽  
Insertional Inactivation ◽  
Two Component ◽  
Genes Encoding ◽  
Dose Dependent

ABSTRACT Streptococcus salivarius 20P3 produces a 22-amino-acid residue lantibiotic, designated salivaricin A (SalA), that inhibits the growth of a range of streptococci, including all strains ofStreptococcus pyogenes. Lantibiotic production is associated with the sal genetic locus comprisingsalA, the lantibiotic structural gene; salBCTXgenes encoding peptide modification and export machinery proteins; andsalYKR genes encoding a putative immunity protein and two-component sensor-regulator system. Insertional inactivation ofsalB in S. salivarius 20P3 resulted in abrogation of SalA peptide production, of immunity to SalA, and ofsalA transcription. Addition of exogenous SalA peptide tosalB mutant cultures induced dose-dependent expression ofsalA mRNA (0.2 kb), demonstrating that SalA production was normally autoregulated. Inactivation of salR encoding the response regulator of the SalKR two-component system led to reduced production of, and immunity to, SalA. The sal genetic locus was also present in S. pyogenes SF370 (M type 1), but because of a deletion across the salBCT genes, the corresponding lantibiotic peptide, designated SalA1, was not produced. However, in S. pyogenes T11 (M type 4) the sallocus gene complement was apparently complete, and active SalA1 peptide was synthesized. Exogenously added SalA1 peptide from S. pyogenes T11 induced salA1 transcription in S. pyogenes SF370 and in an isogenic S. pyogenes T11salB mutant and salA transcription in S. salivarius 20P3 salB. Thus, SalA and SalA1 are examples of streptococcal lantibiotics whose production is autoregulated. These peptides act as intra- and interspecies signaling molecules, modulating lantibiotic production and possibly influencing streptococcal population ecology in the oral cavity.

Postprandial intestinal hyperemia: role of bile salts in the ileum

1981 ◽  
Vol 241 (6) ◽  
pp. G469-G477 ◽  
Author(s):  
P. R. Kvietys ◽  
J. M. McLendon ◽  
D. N. Granger
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Bile Salt ◽  
Bile Salts ◽  
Dependent Manner ◽  
Salt Solutions ◽  
Dose Dependent ◽  
Oxygen Difference ◽  
Artificial Pressure

In an autoperfused dog ileum preparation, artificial pressure, venous outflow pressure, blood flow, and arteriovenous oxygen difference were measured while bile and bile salt solutions, at physiological concentrations, were placed in the lumen. Intraluminal placement of endogenous bile, synthetic bile, or bile salt solutions increased ileal blood flow (99 +/- 10, 94 +/- 20, and 104 +/- 17%, respectively) and oxygen uptake (30 +/- 5, 36 +/- 9, and 28 +/- 5%, respectively). Endogenous bile pretreated with cholestyramine, a bile salt-sequestering resin, did not alter ileal blood flow, yet increased ileal oxygen uptake by 11 +/- 3%, a response similar to that observed while Tyrode's solution (the vehicle) was in the lumen. Intra-arterial infusion of bile salts increased ileal blood flow in a dose-dependent manner, while not significantly altering ileal oxygen uptake. The results of the present study indicate that bile salts play an important role in the functional (postprandial) hyperemia in the ileum by 1) directly dilating the ileal vasculature and 2) enhancing ileal metabolism during their active absorption.

Effect of Conjugated Bile Salts on Antibiotic Susceptibility of Bile Salt–Tolerant Lactobacillus and Bifidobacterium Isolates

2000 ◽  
Vol 63 (10) ◽  
pp. 1369-1376 ◽  
Author(s):  
WILLIAM P. CHARTERIS ◽  
PHILLIP M. KELLY ◽  
LORENZO MORELLI ◽  
J. KEVIN COLLINS
Keyword(s):  
Bile Salt ◽  
Antibiotic Susceptibility ◽  
Bile Salts ◽  
Polymyxin B ◽  
Drug Combinations ◽  
Penicillin G ◽  
Dependent Manner ◽  
Salt Tolerant ◽  
Intrinsic Resistance ◽  
Conjugated Bile Salts

Virtually every antibiotic may cause in vivo alterations in the number, level, and composition of the indigenous microbiotae. The degree to which the microbiotae are disturbed depends on many factors. Although bile may augment antibiotic activity, studies on the effect of bile on the antibiotic susceptibility of indigenous and exogenous probiotic microorganisms are lacking. It was against this background that the antibiotic susceptibility of 37 bile salt–tolerant Lactobacillus and 11 Bifidobacterium isolates from human and other sources was determined in the presence of 0.5% wt/wt oxgall (conjugated bile salts). Oxgall did not affect the intrinsic resistance of lactobacilli to metronidazole (5 μg), vancomycin (30 μg), and cotrimoxazole (25 μg), whereas it resulted in a complete loss of resistance to polymyxin B (300 μg) and the aminoglycosides gentamicin (10 μg), kanamycin (30 μg), and streptomycin (10 μg) for most strains studied (P < 0.001). Oxgall did not affect the intrinsic resistance of bifidobacteria to metronidazole and vancomycin, whereas polymyxin B and co-trimoxazole resistance was diminished (P < 0.05) and aminoglycoside resistance was lost (P < 0.001). Seven lactobacilli, but no bifidobacteria strain, showed unaltered intrinsic antibiotic resistance profiles in the presence of oxgall. Oxgall affected the extrinsic susceptibility of lactobacilli and bifidobacteria to penicillin G (10 μg), ampicillin (10 μg), tetracycline (30 μg), chloramphenicol (30 μg), erythromycin (15 μg), and rifampicin (5 μg) in a source- and strain-dependent manner. Human strain–drug combinations of lactobacilli (P < 0.05) and bifidobacteria (P < 0.01) were more likely to show no change or decreased susceptibility compared with other strain-drug combinations. The antimicrobial activity spectra of polymyxin B and the aminoglycosides should not be considered limited to gram-negative bacteria but extended to include gram-positive genera of the indigenous and transiting microbiotae in the presence of conjugated bile salts. Those lactobacilli (7 of 37) that show unaltered intrinsic and diminished extrinsic antibiotic susceptibility in the presence of oxgall may possess greater upper gastrointestinal tract transit tolerance in the presence of antibiotics.

scholarly journals Polymyxin B–modified upconversion nanoparticles for selective detection of Gram-negative bacteria such as Escherichia coli

2020 ◽  
Vol 44 (11-12) ◽  
pp. 756-761
Author(s):  
Yan Qiao ◽  
Hongchao Geng ◽  
Ning Jiang ◽  
Xingqi Zhu ◽  
Chenyi Li ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Limit Of Detection ◽  
Polymyxin B ◽  
Upconversion Nanoparticles ◽  
Selective Detection ◽  
Gram Negative Bacteria ◽  
Cationic Antimicrobial Peptide ◽  
Gram Negative ◽  
In Vivo Fluorescence Imaging

Upconversion nanoparticles, Yb,Tm,Fe-doped NaYF4 nanoparticles, are synthesized and modified with polymyxin B for the selective detection of Gram-negative bacteria. Polymyxin B, a cyclic cationic antimicrobial peptide which can specifically bind to the lipopolysaccharides of cell wall of Gram-negative bacteria, such as Escherichia coli, is used to target and bind Gram-negative bacteria. The bacteria are then quantified by measuring the fluorescence intensity of the upconversion nanoparticle–bacteria complexes at 801 nm under 980 nm excitation. A limit of detection of 36 CFU/mL is achieved in the detection of Escherichia coli, and Escherichia coli in soybean milk is successfully detected. The limited autofluorescence and photobleaching properties of the upconversion nanoparticles make the proposed method useful for in vivo fluorescence imaging of Gram-negative bacteria.

scholarly journals ZraP is a periplasmic molecular chaperone and a repressor of the zinc-responsive two-component regulator ZraSR

2012 ◽  
Vol 442 (1) ◽  
pp. 85-93 ◽  
Author(s):  
Corinne Appia-Ayme ◽  
Andrea Hall ◽  
Elaine Patrick ◽  
Shiny Rajadurai ◽  
Thomas A. Clarke ◽  
...  
Keyword(s):  
Antimicrobial Agents ◽  
Regulatory System ◽  
Enteric Bacteria ◽  
Polymyxin B ◽  
Regulatory Function ◽  
Cationic Antimicrobial Peptide ◽  
Envelope Stress ◽  
Two Component ◽  
Periplasmic Proteins ◽  
Zinc Concentrations

The bacterial envelope is the interface with the surrounding environment and is consequently subjected to a barrage of noxious agents including a range of compounds with antimicrobial activity. The ESR (envelope stress response) pathways of enteric bacteria are critical for maintenance of the envelope against these antimicrobial agents. In the present study, we demonstrate that the periplasmic protein ZraP contributes to envelope homoeostasis and assign both chaperone and regulatory function to ZraP from Salmonella Typhimurium. The ZraP chaperone mechanism is catalytic and independent of ATP; the chaperone activity is dependent on the presence of zinc, which is shown to be responsible for the stabilization of an oligomeric ZraP complex. Furthermore, ZraP can act to repress the two-component regulatory system ZraSR, which itself is responsive to zinc concentrations. Through structural homology, ZraP is a member of the bacterial CpxP family of periplasmic proteins, which also consists of CpxP and Spy. We demonstrate environmental co-expression of the CpxP family and identify an important role for these proteins in Salmonella's defence against the cationic antimicrobial peptide polymyxin B.

scholarly journals SlyA, a MarR Family Transcriptional Regulator, Is Essential for Virulence in Dickeya dadantii 3937

2009 ◽  
Vol 191 (17) ◽  
pp. 5409-5418 ◽  
Author(s):  
M. Manjurul Haque ◽  
M. Shahinur Kabir ◽  
Luqman Qurata Aini ◽  
Hisae Hirata ◽  
Shinji Tsuyumu
Keyword(s):  
Pathogenic Bacteria ◽  
Pectate Lyase ◽  
Transcriptional Regulator ◽  
Polymyxin B ◽  
In Planta ◽  
Cationic Antimicrobial Peptide ◽  
Dickeya Dadantii ◽  
Increased Sensitivity ◽  
Gene Deletion Mutant ◽  
And Oxidative Stress

ABSTRACT SlyA, a MarR family transcriptional regulator, controls an assortment of biological functions in several animal-pathogenic bacteria. In order to elucidate the functions of SlyA in the phytopathogen Dickeya dadantii (formerly Erwinia chrysanthemi) 3937, a slyA gene deletion mutant (denoted ΔslyA) was constructed. The mutant exhibited increased sensitivity to sodium hypochlorite, the cationic antimicrobial peptide polymyxin B, and oxidative stress. The mutant showed reduced production of pectate lyase and exopolysaccharide and an inability to form a pellicle. The mutant lacking a functional slyA gene showed a significantly reduced ability to cause maceration of potato tubers. Accordingly, the mutant exhibited significantly reduced bacterial growth and failed to hyperinduce pectate lyase production in planta. Introduction of a plasmid containing slyA into the ΔslyA mutant caused all of these phenotypes to recover to wild-type levels. These results suggest that SlyA plays an important role in virulence to plants by positively regulating the expression of multiple pathogenicity-related traits of D. dadantii 3937.

scholarly journals Genetic Analysis of Activation of the Vibrio cholerae Cpx Pathway

2009 ◽  
Vol 191 (16) ◽  
pp. 5044-5056 ◽  
Author(s):  
Leyla Slamti ◽  
Matthew K. Waldor
Keyword(s):  
Vibrio Cholerae ◽  
Stress Responses ◽  
Disulfide Bonds ◽  
Chloride Ions ◽  
Mammalian Host ◽  
Two Component System ◽  
E Coli ◽  
Cpx Pathway ◽  
Sense And Respond ◽  
Molecular Signals

ABSTRACT The Cpx two-component system is thought to mediate envelope stress responses in many gram-negative bacteria and has been implicated in the pathogenicity of several enteric pathogens. While cues that activate the Escherichia coli Cpx system have been identified, the nature of the molecular signals that stimulate this pathway is not well understood. Here, we investigated stimuli that trigger this system in Vibrio cholerae, a facultative pathogen that adapts to various niches during its life cycle. In contrast to E. coli, there was no basal activity of the V. cholerae Cpx pathway under standard laboratory conditions. Furthermore, several known stimuli of the E. coli pathway did not induce expression of this system in V. cholerae. There were no defects in intestinal growth in V. cholerae cpx mutants, arguing against the idea that this pathway promotes V. cholerae adaptation to conditions in the mammalian host. We discovered that chloride ions activate the V. cholerae Cpx pathway, raising the possibility that this signal transduction system provides a means for V. cholerae to sense and respond to alterations in salinity. We used a genetic approach to screen for mutants in which the Cpx pathway is activated. We found that mutations in genes whose products are required for periplasmic disulfide bond isomerization result in activation of the Cpx pathway, suggesting that periplasmic accumulation of proteins with aberrant disulfide bonds triggers the V. cholerae Cpx pathway.

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