Propriétés d'un mutant de Proteus mirabilis résistant au peroxyde d'hydrogène

1979 ◽  
Vol 25 (3) ◽  
pp. 312-320 ◽  
Author(s):  
G. Sauret ◽  
H. Jouve ◽  
J. Pelmont
Keyword(s):  
Hydrogen Peroxide ◽  
Proteus Mirabilis ◽  
Resistant Mutant ◽  
Wild Type ◽  
Membrane Enzyme ◽  
Internal Membrane ◽  
Mutagenic Property ◽  
High Doses

A peroxide-resistant mutant (PR) was isolated from Proteus mirabilis using the hydrogen peroxide mutagenic property. Under the same conditions, resistance of mutant PR bacteria to H2O2 was 50 to 100 times greater than that of the wild type. The total amount of catalase produced by P. mirabilis PR was on the average 10 times greater than that of the wild type. When PR bacteria were subjected to high doses of H2O2 (150 mM), the determination of catalasic activity in vivo increased; paradoxically, there was a net decrease in the activity of the solubilized catalase after the breakdown of the cells. The hypothesis of an enzyme transfer from the inside towards the periphery of the cells is discussed. The behavior of a membrane enzyme (L-phenylalanine oxidase) of the PR mutant shows that H2O2 may cause lesions way up to the internal membrane of bacteria.

Comparison of the PR mutant with the wild-type strain ofProteus mirabilisbrings insight into peroxide resistance factors and regulation of catalase expression

2001 ◽  
Vol 47 (2) ◽  
pp. 130-138 ◽  
Author(s):  
Pierre Andreoletti ◽  
Bruno Franzetti ◽  
Laurent Nussaume ◽  
Jean-Pierre Andrieu ◽  
Jean Gagnon ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Proteus Mirabilis ◽  
Resistant Mutant ◽  
Wild Type ◽  
Resistance Factors ◽  
Alkyl Hydroperoxide ◽  
In The Wild ◽  
Large Production ◽  
Flanking Regions ◽  
Insight Into

The peroxide resistant mutant (PR) of Proteus mirabilis was characterized by an increased constitutive catalase activity concomitant with a large production of specific mRNA. Survival toward hydrogen peroxide during exponential phase was increased by H2O2pretreatment in the wild type but not in the mutant, although the catalase of both strains was not inducible under these conditions. In the mutant, besides catalase, over-produced proteins comprised two different alkyl hydroperoxide reductase subunit C (AhpC) proteins and a protein homologous to the stationary phase transcription factor SspA of Escherichia coli. Conversely, the flagellin A (FlaA) of P. mirabilis was repressed in the PR mutant. Genomic DNA fragments of 2.9 kb carrying the catalase gene (katA) together with the 5' and 3' flanking regions were isolated from both strains and found to be identical. Upstream of katA, a Fur box-like sequence was found, but surprisingly, restricting iron in the culture medium caused a decrease in catalase production. The PR mutant presents similarities with other peroxide resistant mutants, but the regulation of catalase biosynthesis in P. mirabilis seems somewhat different from other close species such as E. coli.Key words: Proteus mirabilis, hydrogen peroxide, peroxide resistant mutant, catalase.

scholarly journals Natural Selection in the Chicken Host Identifies 3-Deoxy-d-manno- Octulosonic Acid Kinase Residues Essential for Phosphorylation of Pasteurella multocida Lipopolysaccharide

2010 ◽  
Vol 78 (9) ◽  
pp. 3669-3677 ◽  
Author(s):  
Marina Harper ◽  
Andrew D. Cox ◽  
Frank St. Michael ◽  
Mark Ford ◽  
Ian W. Wilkie ◽  
...  
Keyword(s):  
Defense Mechanisms ◽  
Pasteurella Multocida ◽  
Inner Core ◽  
Single Amino Acid ◽  
Sequencing Analysis ◽  
Wild Type ◽  
Fowl Cholera ◽  
Mutant Strains ◽  
High Doses

ABSTRACT Pasteurella multocida is the causative agent of a number of diseases in animals, including fowl cholera. P. multocida strains simultaneously express two lipopolysaccharide (LPS) glycoforms (glycoforms A and B) that differ only in their inner core structure. Glycoform A contains a single 3-deoxy-d-manno-octulosonic acid (Kdo) residue that is phosphorylated by the Kdo kinase, KdkA, whereas glycoform B contains two unphosphorylated Kdo residues. We have previously shown that P. multocida mutants lacking the heptosyltransferase, HptA, produce full-length glycoform B LPS and a large amount of truncated glycoform A LPS, as they cannot add heptose to the glycoform A inner core. These hptA mutants were attenuated in chickens because the truncated LPS made them vulnerable to host defense mechanisms, including antimicrobial peptides. However, here we show that birds inoculated with high doses of the hptA mutant developed fowl cholera and the P. multocida isolates recovered from diseased birds no longer expressed truncated LPS. Sequencing analysis revealed that the in vivo-derived isolates had mutations in kdkA, thereby suppressing the production of glycoform A LPS. Interestingly, a number of the spontaneous KdkA mutant strains produced KdkA with a single amino acid substitution (A112V, R123P, H168Y, or D193N). LPS structural analysis showed that complementation of a P. multocida kdkA mutant with wild-type kdkA restored expression of glycoform A to wild-type levels, whereas complementation with any of the mutated kdkA genes did not. We conclude that in P. multocida KdkA, the amino acids A112, R123, H168, and D193 are critical for Kdo kinase function and therefore for glycoform A LPS assembly.

Studies on the carbonic anhydrase activity in Synechocystis PCC6803 wild type and an acetazolamide-resistant mutant

1991 ◽  
Vol 69 (5) ◽  
pp. 1103-1108 ◽  
Author(s):  
S. Bedu ◽  
F. Joset
Keyword(s):  
Carbonic Anhydrase ◽  
Inorganic Carbon ◽  
Physiological Role ◽  
Resistant Mutant ◽  
Carbonic Anhydrase Activity ◽  
Wild Type ◽  
Synechocystis Pcc6803 ◽  
Physiological Analysis ◽  
Carbon Concentrations

The problem of the role and the localization of carbonic anhydrase activity in cyanobacteria has been addressed by two approaches using strain Synechocystis PCC6803. Physiological analysis of the differential effects of carbonic anhydrase inhibitors on the entry and accumulation of CO2 in cells grown under low or high inorganic carbon concentrations and determination of carbonic anhydrase activities in cellular subfractions led to the hypothesis of the presence of two different enzymes in this strain. This conclusion is compatible with current models. Only the internal enzyme could be regulated by variations of the external inorganic carbon concentrations. A parallel analysis of a mutant of this strain resistant to the inhibitor acetazolamide supported the hypothesis of the presence of two enzymes. This clone would be selectively impaired in the carbonic anhydrase activity involved in the maintenance of the internal CO2 pool, while its transport capacity is unchanged. Key words: carbonic anhydrase, physiological role, localization, inhibitors, cyanobacteria, mutant.

scholarly journals In vitro analysis of human immunodeficiency virus type 1 resistance to nevirapine and fitness determination of resistant variants

2002 ◽  
Vol 83 (1) ◽  
pp. 93-101 ◽  
Author(s):  
Maria Dolores Iglesias-Ussel ◽  
Concepción Casado ◽  
Eloísa Yuste ◽  
Isabel Olivares ◽  
Cecilio López-Galíndez
Keyword(s):  
Fold Increase ◽  
Resistant Mutant ◽  
Wild Type ◽  
Resistance Mutations ◽  
Phenotypic Resistance ◽  
Drug Concentrations ◽  
Immunodeficiency Virus ◽  
Vitro Analysis

Nevirapine-resistant variants were generated by serial passages in MT-2 cells in the presence of increasing drug concentrations. In passage 5, mutations V106A, Y181C and G190A were detected in the global population, associated with a 100-fold susceptibility decrease. Sequence analysis of biological clones obtained from passage 5 and subsequent passages showed that single mutants, detected in first passages, were progressively replaced in passage 15 by double mutants, correlating with a 500-fold increase in phenotypic resistance. Fitness determination of single mutants confirmed that, in the presence of nevirapine, every variant was more fit than wild-type with a fitness order Y181C>V106A>G190A>wild-type. Unexpectedly, in the absence of the drug, the Y181C resistant mutant was more fit than wild-type, with a fitness gradient Y181C>wild-type >G106A⩾V190A. Using a molecular clone in which the Y181C mutation was introduced by in vitro mutagenesis, the greater fitness of the Y181C mutant was confirmed in new competition cultures. These data exemplify the role of resistance mutations on virus phenotype but also on virus evolution leading, occasionally, to resistant variants fitter than the wild-type in the absence of the drug.

scholarly journals Mannose-Resistant Proteus-Like Fimbriae Are Produced by Most Proteus mirabilis Strains Infecting the Urinary Tract, Dictate the In Vivo Localization of Bacteria, and Contribute to Biofilm Formation

2004 ◽  
Vol 72 (12) ◽  
pp. 7294-7305 ◽  
Author(s):  
Angela M. Jansen ◽  
Virginia Lockatell ◽  
David E. Johnson ◽  
Harry L. T. Mobley
Keyword(s):  
Urinary Tract ◽  
Proteus Mirabilis ◽  
Biofilm Formation ◽  
Constitutive Expression ◽  
Etiologic Agent ◽  
Phase Variable ◽  
Wild Type ◽  
Bladder Tissue ◽  
Tract Infections

ABSTRACT Proteus mirabilis, an etiologic agent of complicated urinary tract infections, expresses mannose-resistant Proteus-like (MR/P) fimbriae whose expression is phase variable. Here we examine the role of these fimbriae in biofilm formation and colonization of the urinary tract. The majority of wild-type P. mirabilis cells in transurethrally infected mice produced MR/P fimbriae. Mutants that were phase-locked for either constitutive expression (MR/P ON) or the inability to express MR/P fimbriae (MR/P OFF) were phenotypically distinct and swarmed at different rates. The number of P. mirabilis cells adhering to bladder tissue did not appear to be affected by MR/P fimbriation. However, the pattern of adherence to the bladder surface was strikingly different. MR/P OFF colonized the lamina propria underlying exfoliated uroepithelium, while MR/P ON colonized the luminal surfaces of bladder umbrella cells and not the exfoliated regions. Wild-type P. mirabilis was usually found colonizing intact uroepithelium, but it occasionally adhered to exfoliated areas. MR/P ON formed significantly more biofilm than either P. mirabilis HI4320 (P = 0.03) or MR/P OFF (P = 0.05). MR/P OFF was able to form a biofilm similar to that of the wild type. MR/P ON formed a three-dimensional biofilm structure as early as 18 h after the initiation of the biofilm, while MR/P OFF and the wild type did not. After 7 days, however, P. mirabilis HI4320 formed a 65-μm-thick biofilm, while the thickest MR/P ON and MR/P OFF biofilms were only 12 μm thick. We concluded that MR/P fimbriae are expressed by most P. mirabilis cells infecting the urinary tract, dictate the localization of bacteria in the bladder, and contribute to biofilm formation.

The Effect of Chronic Atropine Treatment on Salivary Composition and Caries in Rats

1989 ◽  
Vol 68 (12) ◽  
pp. 1739-1745 ◽  
Author(s):  
G.E. Watson ◽  
S.K. Pearson ◽  
J.L. Falany ◽  
D.J. Culp ◽  
L.A. Tabak ◽  
...  
Keyword(s):  
Chronic Administration ◽  
Cholinergic Receptor ◽  
Blood Levels ◽  
High Dose ◽  
Parotid Saliva ◽  
Sds Page ◽  
Atropine Treatment ◽  
High Doses

Many instances of salivary dysfunction in humans can be traced to the use of medications that have hyposalivary side-effects. In this study, atropine, a cholinergic antagonist, was administered chronically to rats by use of osmotic mini-pumps. Steady-state blood levels, similar to levels obtained in human multiple oral dosing, were thus maintained. Atropine delivered in this manner for 24 days was found to decrease protein concentration of parotid saliva (p<0.05) elicited by pilocarpine, and to increase smooth-surface caries scores (p<0.05) in rats fed a cariogenic diet. Parotid saliva collected via ductal cannulation from rats subjected to chronic atropine administration (and stimulated to secrete by pilocarpine) exhibited increased levels of two basic proline-rich proteins (Peak A and SP-3), as evaluated by SDS-PAGE, compared with those observed in saliva from controls. Cannulation of sublingual glands in animals receiving high doses of atropine produced no measurable secretion upon pilocarpine stimulation. Carbachol stimulation of dispersed cell aggregates of sublingual glands from sham-operated and high-dose atropine groups indicated that the glands responded similarly once the antagonist was washed from the system, implying that the lack of secretion in vivo was caused by antagonism of the cholinergic receptor by atropine. Our observations suggest that this model system can be exploited for determination of the effects of chronic administration of hyposalivary drugs on salivary composition and caries rates.

Seizures in Rats Associated with Divalent Cation Inhibition of Na+–K+-ATP'ase

1971 ◽  
Vol 49 (11) ◽  
pp. 1217-1224 ◽  
Author(s):  
J. Donaldson ◽  
T. St-Pierre ◽  
J. Minnich ◽  
A. Barbeau
Keyword(s):  
Divalent Cation ◽  
Regional Analysis ◽  
Intraventricular Injection ◽  
Specific Inhibition ◽  
Low Doses ◽  
High Doses ◽  
Very High

In vitro determination of rat brain microsomal ATP'ase activity revealed specific inhibition of the Na+–K+-ATP'ase by cations in the order Zn2+ > Cu2+ > Fe2+ > Mn2+. Intraventricular injection of the same cations or of ouabain resulted in convulsions. Regional analysis of ATP'ase from brains of rats after convulsions showed inhibited Na+–K+-ATP'ase activity in hippocampus and hypothalamus. Hippocampus and hypothalamus were found to have the highest Na+–K+-ATP'ase activity in the rat brain.The potent inhibitors of Na+–K+-ATP'ase in vitro (ouabain, Zn2+, and Cu2+) were similarly effective in vivo (hippocampus and hypothalamus), while the inhibitors relatively ineffective in vitro (Fe2+ and Mn2+) were similarly of low potency in vivo. The potent inhibitors of Na+–K+-ATP'ase caused convulsions at low doses; the ineffective inhibitors caused convulsions only at very high doses.

Role of Cu,Zn-SOD in the synthesis of endogenous vasodilator hydrogen peroxide during reactive hyperemia in mouse mesenteric microcirculation in vivo

2008 ◽  
Vol 294 (1) ◽  
pp. H441-H448 ◽  
Author(s):  
Toyotaka Yada ◽  
Hiroaki Shimokawa ◽  
Keiko Morikawa ◽  
Aya Takaki ◽  
Yoshiro Shinozaki ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Reactive Hyperemia ◽  
Fluorescent Microscopy ◽  
Artery Occlusion ◽  
Wild Type ◽  
Charge Coupled Device ◽  
In The Wild ◽  
Mesenteric Microcirculation

We have recently demonstrated that endothelium-derived hydrogen peroxide (H2O2) is an endothelium-derived hyperpolarizing factor and that endothelial Cu/Zn-superoxide dismutase (SOD) plays an important role in the synthesis of endogenous H2O2 in both animals and humans. We examined whether SOD plays a role in the synthesis of endogenous H2O2 during in vivo reactive hyperemia (RH), an important regulatory mechanism. Mesenteric arterioles from wild-type and Cu,Zn-SOD−/− mice were continuously observed by a pencil-type charge-coupled device (CCD) intravital microscope during RH (reperfusion after 20 and 60 s of mesenteric artery occlusion) in the cyclooxygenase blockade under the following four conditions: control, catalase alone, NG-monomethyl-l-arginine (l-NMMA) alone, and l-NMMA + catalase. Vasodilatation during RH was significantly decreased by catalase or l-NMMA alone and was almost completely inhibited by l-NMMA + catalase in wild-type mice, whereas it was inhibited by l-NMMA and l-NMMA + catalase in the Cu,Zn-SOD−/− mice. RH-induced increase in blood flow after l-NMMA was significantly increased in the wild-type mice, whereas it was significantly reduced in the Cu,Zn-SOD−/− mice. In mesenteric arterioles of the Cu,Zn-SOD−/− mice, Tempol, an SOD mimetic, significantly increased the ACh-induced vasodilatation, and the enhancing effect of Tempol was decreased by catalase. Vascular H2O2 production by fluorescent microscopy in mesenteric arterioles after RH was significantly increased in response to ACh in wild-type mice but markedly impaired in Cu,Zn-SOD−/− mice. Endothelial Cu,Zn-SOD plays an important role in the synthesis of endogenous H2O2 that contributes to RH in mouse mesenteric smaller arterioles.

Properties of a catalase from a peroxide-resistant mutant of Proteus mirabilis

1983 ◽  
Vol 61 (11) ◽  
pp. 1219-1227 ◽  
Author(s):  
Hélène M. Jouve ◽  
Christiane Lasauniere ◽  
Jean Pelmont
Keyword(s):  
Proteus Mirabilis ◽  
Specific Activity ◽  
Resistant Mutant ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Beef Liver ◽  
Specific Antibodies ◽  
Isoelectric Ph

A catalase (EC 1.11.1.6) from Proteus mirabilis PR, a mutant with strong resistance to hydrogen peroxide, was purified to homogeneity and compared with catalase from wild-type P. mirabilis. In crude extracts from the mutant, catalase was present as two different entities called A and B, that could be resolved by ion-exchange chromatography. The B form was transformed into A. The pure catalase preparation contained the A form only. This catalase was not found to be different from the wild-type enzyme, considering its molecular weight, subunit composition, isoelectric pH, and reactivity to specific antibodies. Partial proteolytic cleavage of the two bacterial enzymes with four different proteases proceeded at the same rate and produced identical patterns. However, pure catalase from the mutant had a specific activity against H2O2 of 2.7 × 107M−1∙s−1, and its purity index (A406/A280) was 1.12. These values were higher than previously determined for the wild-type enzyme. Furthermore, the mutant catalase was more stable to heat. The results suggest that the purified catalase (A form) differs from the wild-type enzyme and appears to be a more efficient catalase against H2O2. Both enzymes were found to be much more resistant than beef liver catalase to the classically used catalase inhibitor 3-amino-1,2,4-triazole.

scholarly journals Tissue Inhibitor of Metalloproteinase-1 (TIMP-1) Deficient Mice Display Reduced Serum Progesterone Levels during Corpus Luteum Development

Endocrinology ◽  
2003 ◽  
Vol 144 (1) ◽  
pp. 5-8 ◽  
Author(s):  
Warren B. Nothnick
Keyword(s):  
Corpus Luteum ◽  
Tissue Inhibitor Of Metalloproteinase ◽  
Wild Type ◽  
Serum Progesterone ◽  
Multifunctional Protein ◽  
Progesterone Production ◽  
In The Wild

Abstract TIMP-1 is a multifunctional protein that is abundantly expressed within the ovary during the period of early corpus luteum formation. TIMP-1 has been suggested to play a role in progesterone production, but reports are conflicting. To more thoroughly examine the role of TIMP-1 in steroidogenesis during early luteal development in vivo, immature wild-type and TIMP-1 null female mice were primed with gonadotropins. Mice were sacrificed at 0, 24, and 48 h post hCG administration and serum was collected for determination of estradiol (E2) or progesterone (P4) concentrations. In the 24 h hCG groups, ovulation was assessed by counting the number of shed ova. Serum P4 concentrations were significantly lower in the TIMP-1 null mice, both at 24 and 48-h post hCG compared to wild-type counterparts. No differences were detected in the number of ovulations between genotypes at the 24 h time point. In both the 24 and 48 h post-hCG groups, null mice had significantly higher ovarian wet weights. Interestingly, ovarian MMP activity was greater in the null mice at 24 h post hCG but higher in the wild-type at 48 h post hCG administration. These observations suggests that expression of TIMP-1 during early luteal development may participate in regulation of progesterone production via its ability to regulate ovarian MMP activity.

Sign in / Sign up

Export Citation Format

Share Document