Conserved amphiphilic feature is essential for periplasmic chaperone HdeA to support acid resistance in enteric bacteria

2008 ◽  
Vol 412 (2) ◽  
pp. 389-397 ◽  
Author(s):  
Ye E. Wu ◽  
Weizhe Hong ◽  
Chong Liu ◽  
Lingqing Zhang ◽  
Zengyi Chang
Keyword(s):  
Pathogenic Bacteria ◽  
Acid Resistance ◽  
Enteric Bacteria ◽  
Structural Features ◽  
Low Ph ◽  
Hydrophobic Region ◽  
Ph Values ◽  
Ph Conditions ◽  
Stomach Ph ◽  
Ph Range

The extremely acidic environment of the mammalian stomach (pH 1–3) represents a stressful challenge for enteric pathogenic bacteria, including Escherichia coli, Shigella and Brucella. The hdeA (hns-dependent expression A) gene was found to be crucial for the survival of these enteric bacteria under extremely low pH conditions. We recently demonstrated that HdeA is able to exhibit chaperone-like activity exclusively within the stomach pH range by transforming from a well-folded conformation at higher pH values (above pH 3) into an unfolded conformation at extremely low pH values (below pH 3). This study was performed to characterize the action mechanisms and underlying specific structural features for HdeA to function in this unfolded conformation. In the present study, we demonstrate that the conserved ‘amphiphilic’ feature of HdeA, i.e. the exposure of the conserved hydrophobic region and highly charged terminal regions, is essential for exhibiting chaperone-like activity under extremely low pH conditions. Mutations that disrupt this amphiphilic feature markedly reduced the chaperone-like activity of HdeA. The results also strongly suggest that this acid-induced chaperone-like activity of HdeA is crucial for acid resistance of the enteric bacteria. Moreover, our new understanding of this amphiphilic structural feature of HdeA helps to better interpret how this unfolded (disordered) conformation could be functionally active.

scholarly journals Chemoenzymatic synthesis of the pH responsive surfactant octyl β-D-glucopyranoside uronic acid

2019 ◽  
Vol 104 (3) ◽  
pp. 1055-1062 ◽  
Author(s):  
Ngoc T. N. Ngo ◽  
Carl Grey ◽  
Patrick Adlercreutz
Keyword(s):  
Substrate Concentration ◽  
Uronic Acid ◽  
Catalyst System ◽  
Low Ph ◽  
Chemoenzymatic Synthesis ◽  
Ph Responsive ◽  
Ph Values ◽  
Wide Ph Range ◽  
Carboxyl Derivative ◽  
Ph Range

AbstractMethodology was developed to expand the range of benign alkyl glycoside surfactants to include also anionic types. This was demonstrated possible through conversion of the glycoside to its carboxyl derivative. Specifically, octyl β-D-glucopyranoside (OG) was oxidised to the corresponding uronic acid (octyl β-D-glucopyranoside uronic acid, OG-COOH) using the catalyst system T. versicolor laccase/2,2,6,6-tetramethylpiperidinyloxy (TEMPO) and oxygen from air as oxidant. The effects of oxygen supply methodology, concentrations of laccase, TEMPO and OG as well as reaction temperature were evaluated. At 10 mM substrate concentration, the substrate was almost quantitatively converted into product, and even at a substrate concentration of 60 mM, 85% conversion was reached within 24 h. The surfactant properties of OG-COOH were markedly dependent on pH. Foaming was only observed at low pH, while no foam was formed at pH values above 5.0. Thus, OG-COOH can be an attractive low-foaming surfactant, for example for cleaning applications and emulsification, in a wide pH range (pH 1.5–10.0).

Survival of Bacillus cereus Vegetative Cells and Spores during In Vitro Simulation of Gastric Passage

2012 ◽  
Vol 75 (4) ◽  
pp. 690-694 ◽  
Author(s):  
SIELE CEUPPENS ◽  
MIEKE UYTTENDAELE ◽  
KATRIEN DRIESKENS ◽  
ANDREJA RAJKOVIC ◽  
NICO BOON ◽  
...  
Keyword(s):  
Bacillus Cereus ◽  
Acid Resistance ◽  
In Vitro Experiments ◽  
Vegetative Cells ◽  
Ph Values ◽  
Constant Ph ◽  
In Vitro Simulation ◽  
Ph Range

The enteric pathogen Bacillus cereus must survive gastric passage in order to cause diarrhea by enterotoxin production in the small intestine. The acid resistance and the survival after gastric passage were assessed by in vitro experiments with acidified growth medium and gastric simulation medium with B. cereus NVH 1230-88 vegetative cells and spores. First, batch incubations at constant pH values for 4 h, which represented different physiological states of the stomach, showed that spores were resistant to any gastric condition in the pH range of 2.0 to 5.0, while vegetative cells were rapidly inactivated at pH values of ≤4.0. Second, a dynamic in vitro gastric experiment was conducted that simulated the continuously changing in vivo conditions due to digestion dynamics by gradually decreasing the pH from 5.0 to 2.0 and fractional emptying of the stomach 30 to 180 min from the start of the experiment. All of the B. cereus spores and 14% (±9%) of the vegetative cells survived the dynamic simulation of gastric passage.

Hydrothermal crystallization kinetics of m-ZrO2 and t-ZrO2

1990 ◽  
Vol 5 (11) ◽  
pp. 2698-2705 ◽  
Author(s):  
Raymond P. Denkewicz ◽  
Kevor S. TenHuisen ◽  
James H. Adair
Keyword(s):  
Crystallization Kinetics ◽  
Low Ph ◽  
Formation Mechanisms ◽  
Gel Structure ◽  
Hydrothermal Conditions ◽  
High Ph ◽  
Ph Values ◽  
Ph Conditions ◽  
Apparent Activation Energies ◽  
Kinetics Of

The isothermal nucleation and crystallization kinetics of hydrothermally prepared monoclinic and tetragonal ZrO2 have been determined at various pH conditions. It is shown that monoclinic ZrO2 precipitates at low pH whereas at high pH tetragonal ZrO2 crystallizes from an amorphous zirconium (hydrous) oxide, Zr(OH)xOy, precursor. At intermediate pH conditions mixtures of the polymorphs are formed suggestive of kinetically competing particle formation mechanisms. The data are explained by the proposed existence of three controlling regimes for the formation of crystalline ZrO2: dissolution/precipitation at low pH, a solubility controlled regime at intermediate pH values, and a gel structure controlled regime at high pH. Apparent activation energies for the nucleation and crystallization of monoclinic and tetragonal ZrO2 formed under hydrothermal conditions are presented.

Solubility of Niobium(V) under Cementitious Conditions: Importance of Ca-niobate

2004 ◽  
Vol 824 ◽  
Author(s):  
Caterina Talerico ◽  
Michael Ochs ◽  
Eric Giffaut
Keyword(s):  
Solid Phase ◽  
Empirical Relation ◽  
Oxide Phase ◽  
X Ray Diffraction ◽  
Ph Values ◽  
Wide Range ◽  
Ph Conditions ◽  
Predicted Values ◽  
Ph Range ◽  
Good Agreement

AbstractThe solubility of niobium was investigated for Ca and pH conditions relevant for cementequilibrated solutions. For the pH range considered (9.5-13.2), the dissolved Nb concentration decreases with increasing pH. Overall, experiments lead to Nb concentrations between 2·10-5 M and 2·10-9 M. For all pH values, the dissolved Nb concentration also decreases systematically with increasing Ca concentration. X-ray diffraction measurements of selected experiments confirmed the presence of a solid Ca-Nb-oxide phase, with CaNb4O11·8H2O (hochelagaite) being the most likely composition. On the basis of these findings an empirical regression model for the prediction of Nb solubility data as a function of pH and Ca concentration was derived. This empirical relation is consistent with the presence of a solubility limiting Ca-Nb solid phase and permits to predict aqueous Nb solubility values in cementitious environments over a relatively wide range of conditions. Predicted values are in good agreement with independent experimental results.

scholarly journals Does the natural carcinogen ptaquiloside degrade readily in groundwater?

2021 ◽  
Vol 33 (1) ◽  
Author(s):  
Jane S. Wu ◽  
Frederik Clauson-Kaas ◽  
Dan Nybro Lindqvist ◽  
Lars Holm Rasmussen ◽  
Bjarne W. Strobel ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Drinking Water ◽  
Degradation Kinetics ◽  
Low Ph ◽  
Experimental Conditions ◽  
Neutral Ph ◽  
Rate Of Hydrolysis ◽  
Acidic Conditions ◽  
Ph Conditions ◽  
Ph Range

Abstract Background Ptaquiloside (PTA) is a natural carcinogen found in bracken ferns. PTA is released from the plants via soil to surface and groundwaters from where humans can be exposed via drinking water. Primary degradation of PTA is due to hydrolysis with formation of pterosin B (PTB). Temperature and pH determine the rate of hydrolysis under pure experimental conditions. To assess the applicability of the experimental model to natural groundwaters, PTA degradation kinetics were examined in a range of natural groundwaters at environmentally relevant conditions. Results PTA was quantified by UPLC-MS/MS. Over an 80-day study period, PTA half-lives ranged from 6.5 to 47 days (natural pH; 8.0 °C). The fastest degradation was observed for the most alkaline groundwaters with pH of around 8. Rates of degradation were well predicted using an existing mathematical model for hydrolysis. However, deviations from this model were found, especially at the extremes of the examined pH-range (4.7–8.2). The degree of conversion of PTA to PTB was close to unity around neutral pH. However, at slightly acidic conditions, formation of PTB could only count for 9% of the degraded PTA, indicating formation of other products. Conclusions Degradation of PTA in groundwater is determined by pH and temperature, and PTA can prevail for months under slightly acid to neutral pH conditions. The existing laboratory-based model for PTA hydrolysis is generally applicable for groundwaters but needs further validation at high and low pH.

scholarly journals Uji Ketahanan Bakteri Asam Laktat Hasil Fermentasi Kubis Merah ( Brassica oleracea L.) Pada pH 3

Jurnal MIPA ◽  
2018 ◽  
Vol 7 (2) ◽  
pp. 20 ◽  
Author(s):  
Kevin V. Bawole ◽  
Stella D. Umboh ◽  
Trina E. Tallei
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Acid Resistance ◽  
Low Ph ◽  
The Body ◽  
Probiotic Bacteria ◽  
Red Cabbage ◽  
Ph Conditions ◽  
The Right ◽  
Brassica Oleracea L

Probiotik merupakan mikroorganisme hidup yang jika dikonsumsi dalam jumlah yang tepat dapat memberikan manfaat bagi tubuh. Sebagian besar bakteri asam laktat merupakan bakteri probiotik. Untuk dapat memberikan manfaat yang maksimal bagi tubuh, salah satu kriteria yang harus dipenuhi yaitu mampu bertahan hidup pada kondisi pH yang rendah. Hal ini dikarenakan bakteri probiotik akan menghadapi kondisi pH rendah yang terdapat di lambung. Penelitian ini bertujuan untuk menguji kemampuan isolat BAL hasil fermentasi kubis merah untuk bertahan hidup pada pH 3. Bakteri asam laktat ditumbuhkan pada media MRS agar yang ditambahkan 1% CaCO3 dengan menggunakan metode sebar (spread) dan dimurnikan menggunakan metode gores (streak). Uji ketahanan asam dilakukan dengan cara isolat diinkubasi pada kondisi pH 3 dalam media NB kemudian ditumbuhkan kembali pada media NA dengan menggunakan metode spread. Uji dilakukan juga untuk mengamati aktivitas enzim katalase. Hasil penelitian menunjukkan bahwa isolat yang diperoleh dari hasil fermentasi kubis merah mampu bertahan pada pH 3.Probiotics is a livinng microorganism that if consumed in the right amount can provide  benefits to the body. Most lactic acid bacteria are probiotic bacteria. To be able to provide maximum benefits for the body, one of the criteria that must be met is able to survive at low pH. This is because probiotic bacteria will face low pH conditions found in the stomach. This study aims to test the effectiveness of BAL isolates from red cabbage fermentation to survie at pH 3.  Lactic acid bacteria grown on MRSA media added 1% CaCO3 by using spread method and purified by using streak method. The acid resistance test was performed by isolate incubated at pH 3 condition in NB medium by using spread method. Test were also conducted to observe the activity of catalase enzymes. The result showed that isolates obtained from red cabbage fermentation were able to survive at pH 3.

Investigation of the Range of a Plastic pH Sensor Based on a Dibasic Ionophore

1992 ◽  
Vol 45 (2) ◽  
pp. 435 ◽  
Author(s):  
TJ Cardwell ◽  
RW Cattrall ◽  
LW Deady ◽  
KA Murphy
Keyword(s):  
Positive Charge ◽  
Ph Sensor ◽  
Low Ph ◽  
Membrane Electrode ◽  
Neutral Carrier ◽  
Ph Values ◽  
Response Range ◽  
Ph Scale ◽  
Ph Range ◽  
Sensitive Membrane

A study is reported of the use of a neutral carrier reagent containing two nitrogen atoms with very different basicities in a pH-sensitive membrane electrode with a view to obtaining a broad response range. This electrode responds well in the pH region of 6-12 but suffers anion interference in the region of pH 2-6. A study is included of the effect of adding various amounts of potassium tetrakis(4-chloropheny1)borate as an anion suppressing reagent to the membrane in order to reduce the anion interference at low pH values. The conclusion is drawn that an extension to the working pH range is not possible with this approach unless controlled amounts of anion suppressing reagent can be provided to approximately balance the positive charge of the carrier in each region of the pH scale.

Antibacterial Protection by Enterocin AS-48 in Sport and Energy Drinks with Less Acidic pH Values

2009 ◽  
Vol 72 (4) ◽  
pp. 881-884 ◽  
Author(s):  
PILAR MARTINEZ VIEDMA ◽  
HIKMATE ABRIOUEL ◽  
NABIL BEN OMAR ◽  
ROSARIO LUCAS LÓPEZ ◽  
EVA VALDIVIA ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Pathogenic Bacteria ◽  
Dental Health ◽  
Energy Drinks ◽  
Low Ph ◽  
Final Concentration ◽  
Acidic Ph ◽  
Time Increase ◽  
Natural Preservative ◽  
Ph Values

The low pH and acid content found in sports and energy drinks are a matter of concern in dental health. Raising the pH may solve this problem, but at the same time increase the risks of spoilage or presence of pathogenic bacteria. In the present study, commercial energy drinks were adjusted to pH 5.0 and challenged with Listeria monocytogenes (drinks A to F), Staphylococcus aureus, Bacillus cereus, and Bacillus licheniformis (drink A) during storage at 37°C. L. monocytogenes was able to grow in drink A and survived in drinks D and F for at least 2 days. Addition of enterocin AS-48 (1 μg/ml final concentration) rapidly inactivated L. monocytogenes in all drinks tested. S. aureus and B. cereus also survived quite well in drink A, and were completely inactivated by 12.5 μg/ml enterocin AS-48 after 2 days of storage or by 25 μg/ml bacteriocin after 1 day. B. licheniformis was able to multiply in drink A, but it was completely inactivated by 5 μg/ml enterocin AS-48 after 2 days of storage or by 12.5 μg/ml bacteriocin after 1 day. Results from the present study suggest that enterocin AS-48 could be used as a natural preservative against these target bacteria in less acidic sport and energy drinks.

Interaction of dimethyltin(IV)dichloride with 5′-AMP and 5′-GMP

2006 ◽  
Vol 84 (11) ◽  
pp. 1534-1540 ◽  
Author(s):  
Farrokh Gharib ◽  
Elnaz Farzad ◽  
Mostafa Mohammadpour Amini
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Ftir Spectroscopy ◽  
Constant Temperature ◽  
Elemental Analysis ◽  
Formation Constants ◽  
Low Ph ◽  
Ph Values ◽  
Species Formation ◽  
Ph Range

The formation constants of the species formed in the systems H+ + dimethyltin(IV) + 5′-AMP and 5′-GMP, H+ + 5′-AMP, and H+ + 5′-GMP have been determined in aqueous solution in the pH range of 1.5–9 at constant temperature (25 °C) and constant ionic strength (0.1 mol dm–3, NaClO4) using spectrophotometric and potentiometric techniques. 1H and 31P NMR investigations in aqueous solution confirmed the species formation and led us to propose their structures. The precipitated complexes of AMP and GMP by Me2Sn(IV)2+ at low pH values were characterized by elemental analysis and FTIR spectroscopy, which ruled out purine moiety (N-1 and N-7) coordination and a bidentated coordination of the phosphate group is concluded in both cases.Key words: dimethyltin(IV)dichloride, guanosine 5′-monophosphate, adenosine 5′-monophosphate, stability and protonation constants.

scholarly journals Does the Natural Carcinogen Ptaquiloside Degrade Readily in Groundwater?

2020 ◽  
Author(s):  
Jane S. Wu ◽  
Frederik Clauson-Kaas ◽  
Dan Nybro Lindqvist ◽  
Lars Holm Rasmussen ◽  
Bjarne W. Strobel ◽  
...  
Keyword(s):  
Drinking Water ◽  
Rate Equation ◽  
Degradation Kinetics ◽  
Low Ph ◽  
Experimental Conditions ◽  
Neutral Ph ◽  
Rate Of Hydrolysis ◽  
Acidic Conditions ◽  
Ph Conditions ◽  
Ph Range

Abstract Background: Ptaquiloside (PTA) is a natural carcinogen found in bracken ferns. PTA is released from the plants via soil to surface and groundwaters from where humans can be exposed via drinking water. Primary degradation of PTA is due to hydrolysis with formation of pterosin B (PTB). Temperature and pH determine the rate of hydrolysis under pure experimental conditions. To assess the applicability of the experimental model to natural groundwaters, PTA degradation kinetics were examined in a range of natural groundwaters at environmentally relevant conditions.Results: PTA was quantified by UPLC-MS/MS. Over an 80-day study period, PTA half-lives ranged from 6.5 to 47 days (natural pH; 8.0oC). The fastest degradation was observed for the most alkaline groundwaters with pH of around 8. Rates of degradation was well predicted using an existing rate equation for hydrolysis. However, deviations from this model were found, especially at the extremes of the examined pH-range (4.7-8.2). The rate of conversion of PTA to PTB was close to unity around neutral pH. However, at slightly acidic conditions, formation of PTB could only count for 9% of the degraded PTA, indicating formation of other products.Conclusions: Degradation of PTA in groundwater is determined by pH and temperature, and PTA can prevail for months under slightly acid to neutral pH conditions. The existing laboratory-based model for PTA hydrolysis is generally applicable for groundwaters but needs further validation at high and low pH.

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