The activation of β-galactosidase (E.coli) by Mg2+at lower pH values

1996 ◽  
Vol 74 (2) ◽  
pp. 295-298 ◽  
Author(s):  
Mercedes Martinez-Bilbao ◽  
Reuben E. Huber
Keyword(s):  
Glutamic Acid ◽  
Key Words ◽  
Free Enzyme ◽  
Site Analysis ◽  
E Coli ◽  
Ph Values ◽  
Low Levels ◽  
High Concentrations ◽  
High Level ◽  
Very High

The activation of β-galactosidase (E. coli) by Mg2+at pH values below 7.6 was studied. If the Mg2+concentration was high enough, the kcatvalues at pH values down to 5.0 remained at the same high level as at pH 7 and 7.6 (600–620 s−1with o-nitrophenyl-β-D-galactopyranoside as the substrate). Very high concentrations of Mg2+(greater than 100 mM at pH 5) were, however, needed to saturate the Mg2+site at lower pH values. The Kmvalues at low levels of Mg2+were high at every pH but they decreased and approached the same low value at every pH (about 0.13 mM) as the [Mg2+] was increased. These data indicate that it is difficult to bind Mg2+at lower pH values, but the kcatand Kmvalues of the enzyme, and therefore the rates of galactosylation (k2), degalactosylation (k3), and binding (Ks), do not change substantially as a function of pH provided that a Mg2+is bound to the enzyme. The data also showed that Mg2+and protons compete for the same site. Analysis by plotting log [Mg2+]midvs. pH showed that the binding of Mg2+to the free enzyme involves two groups with pKavalues in the vicinity of 7 and one group with a pKavalue near 5.5. (The values referred to as [Mg2+]midare the Mg2+concentrations that resulted in kcatvalues midway between basal and maximum.) The "apparent" pKavalues of the groups when a Mg2+was bound (at saturating [Mg2+]) all appeared to be below 5.0.Key words: β-galactosidase, magnesium, pH, activation, glutamic acid, histidine, binding.

scholarly journals Identification of Escherichia coli Genes Essential for High-Level, Clinically Relevant, Resistance to Antibiotics

2021 ◽  
Author(s):  
Esmeralda Z Reyes Fernandez ◽  
Noemie Alon Cudkowicz ◽  
Sonia Steiner Mordoch ◽  
Shimon Schuldiner
Keyword(s):  
Escherichia Coli ◽  
Antibiotic Resistance ◽  
Molecular Mechanisms ◽  
E Coli ◽  
Novel Approach ◽  
Public Health Challenges ◽  
High Concentrations ◽  
New Perspective ◽  
High Level ◽  
Very High

Antibiotic resistance is one of the biggest public health challenges of our time. Here we present a novel approach to recognizing molecular mechanisms essential for maintaining high-level clinically relevant antibiotic resistance. To identify essential genes in this context, we subjected Escherichia coli EV18, a strain highly resistant to quinolones, to random transposon mutagenesis. This strain's unique advantage is that the screen is performed at very high concentrations of the antibiotic, non-permissive for most strains. The transposon's insertion affected the transcription of five genes required for the maintenance of resistance in EV18. Three of these genes (YihO, YhdP, and WaaY) have not been previously identified as essential for high-level antimicrobial resistance (AMR). Our work provides a new perspective to identify and characterize novel players crucial for maintaining AMR in E. coli.

Objectives and Review of the International Milk Fluoridation Program

1995 ◽  
Vol 9 (2) ◽  
pp. 110-111 ◽  
Author(s):  
G.N. Pakhomo
Keyword(s):  
Dental Caries ◽  
National Level ◽  
Data Bank ◽  
Epidemiological Studies ◽  
Weighted Mean ◽  
Number Of Children ◽  
The World ◽  
Low Levels ◽  
High Level ◽  
Very High

The WHO Global Oral Data Bank (GODB) demonstrates wide varieties of dental caries levels. During the last 10 years, dental caries prevalence in many countries has decreased from very high and high to moderate and low levels. However, there also are countries where dental caries has increased from very low and low to a moderate level. In total in 1993, of the 158 countries for which the WHO GODB has data available, 16 countries indicate a very low level (69 - low, 53 - moderate, 17 - high), and only three a very high level of dental caries. Very high levels of dental caries have been recorded in Costa Rica, Jamaica, and Uruguay. All these data, based on the weighted mean of DMF in 12-year-old children, have been obtained from national surveys or collected from published papers on oral health surveys conducted in selected areas of the countries. Very often, these papers indicated an increase (or decrease) in dental caries in people living in different areas of a particular country; however, the DMF weighted mean at the national level is still without change. One of the most populated countries in the world, China, shows clear evidence from several recent epidemiological studies that the level of dental caries in the urban population is persistently increasing. Dental caries still remains one of the most common diseases affecting a substantial number of children and adults around the world. There is evidence that water or

scholarly journals Evaluation of an overnight non-culture test for detection of viable Gram-negative bacteria in endoscope channels

2019 ◽  
Vol 07 (02) ◽  
pp. E268-E273 ◽  
Author(s):  
Harminder Singh ◽  
Donald Duerksen ◽  
Gale Schultz ◽  
Carol Reidy ◽  
Pat DeGagne ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Rapid Test ◽  
Gram Negative Bacteria ◽  
Clinical Workflow ◽  
Gram Negative ◽  
E Coli ◽  
Test Kit ◽  
Viable Bacteria ◽  
Low Levels ◽  
High Level

Abstract Background and study aims Prevention of infection transmission from contaminated endoscopes would benefit from a rapid test that could detect low levels of viable bacteria after high level disinfection. The aim of this study was to evaluate the rapid NOW! (RN) test’s ability to detect endoscope contamination. Materials and methods The RN test kit and the accompanying fluorometer were evaluated. The manufacturer states that a fluorometer signal > 300 units is indicative of viable Gram-negative bacteria. Suspension testing of varying concentrations of Escherichia coli, Pseudomonas aeruginosa and Enterococcus faecalis were used to determine the RN test limit of detection. Simulated-use testing was done using a duodenoscope inoculated with 10 % blood containing approximately 35 CFU E. coli per channel. Samples were extracted from the duodenoscope instrument channel and tested using the manufacturer’s instructions. Results The RN test could consistently detect 10 CFU of E. coli and P. aeruginosa (fluorescent signal of 9,000 to 11,000 units) but not E. faecalis. Sensitivity and specificity for Gram-negative bacteria were 93 % and 90 %, respectively, using all of the suspensions in the study. Extraction of E. coli from an inoculated duodenoscope instrument channel repeatedly provided a positive signal (i. e. > 2,000 units). Conclusions The RN test can reliably detect low levels of Gram-negative bacteria in suspension as well as from samples extracted from endoscope channels. These preliminary findings are encouraging but further assessment of extraction efficacy, impact of organic residuals and clinical workflow are still needed.

A Mechanism of Resistance to Hydrogen Peroxide inVibrio rumoiensis S-1

1999 ◽  
Vol 65 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Nobutoshi Ichise ◽  
Naoki Morita ◽  
Tamotsu Hoshino ◽  
Kosei Kawasaki ◽  
Isao Yumoto ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Catalase Activity ◽  
Processing Plant ◽  
Spontaneous Mutant ◽  
Gene Encoding ◽  
E Coli ◽  
Mechanism Of Resistance ◽  
High Concentrations ◽  
Almost All ◽  
Very High

ABSTRACT A possible mechanism of resistance to hydrogen peroxide (H2O2) in Vibrio rumoiensis, isolated from the H2O2-rich drain pool of a fish processing plant, was examined. When V. rumoiensiscells were inoculated into medium containing either 5 mM or no H2O2, they grew in similar manners. A spontaneous mutant strain, S-4, derived from V. rumoiensisand lacking catalase activity did not grow at all in the presence of 5 mM H2O2. These results suggest that catalase is inevitably involved in the resistance and survival of V. rumoiensis in the presence of H2O2. Catalase activity was constitutively present in V. rumoiensis cells grown in the absence of H2O2, and its occurrence was dependent on the age of the cells, a characteristic which is observed for the HP II-type catalase of Escherichia coli. The presence of the HP II-type catalase in V. rumoiensis cells was evidenced by partial sequencing of the gene encoding the HP II-type catalase from this organism. A notable difference between V. rumoiensisand E. coli is that catalase is accumulated at very high levels (∼2% of the total soluble proteins) in V. rumoiensis, in contrast to the case for E. coli. WhenV. rumoiensis cells which had been exposed to 5 mM H2O2 were centrifuged, most intracellular proteins, including catalase, were recovered in the medium. On the other hand, when V. rumoiensis cells were grown on plates containing various concentrations of H2O2, individual cells had a colony-forming ability inferior to those ofE. coli, Bacillus subtilis, and Vibrio parahaemolyticus. Thus, it is suggested that when V. rumoiensis cells are exposed to high concentrations of H2O2, most cells will immediately be broken by H2O2. In addition, the cells which have had little or no damage will start to grow in a medium where almost all H2O2 has been decomposed by the catalase released from broken cells.

scholarly journals Constitutive High Level Expression of an Endoxylanase Gene from the Newly IsolatedBacillus subtilisAQ1 inEscherichia coli

2010 ◽  
Vol 2010 ◽  
pp. 1-12 ◽  
Author(s):  
Is Helianti ◽  
Niknik Nurhayati ◽  
Maria Ulfah ◽  
Budiasih Wahyuntari ◽  
Siswa Setyahadi
Keyword(s):  
Specific Activity ◽  
Biochemical Properties ◽  
Extracellular Expression ◽  
High Level Expression ◽  
Periplasmic Fraction ◽  
16S Rdna Sequence ◽  
E Coli ◽  
Encoding Gene ◽  
High Level ◽  
Very High

A xylanolytic bacterium was isolated from the sediment of an aquarium. Based on the 16S rDNA sequence as well as morphological and biochemical properties the isolate was identified and denoted asBacillus subtilis(B. subtilis) AQ1 strain. An endoxylanase-encoding gene along with its indigenous promoter was PCR amplified and after cloning expressed inE. coli. InE. colithe recombinant enzyme was found in the extracellular, in the cytoplasmic, and in the periplasmic fraction. The specific activity of the extracellular AQ1 recombinant endoxylanase after 24-hour fermentation was very high, namely,2173.6 ± 51.4and2745.3 ± 11 U/mg in LB and LB-xylan medium, respectively. This activity was clearly exceeding that of the nativeB. subtilisAQ1 endoxylanase and that of 95% homologous recombinant one fromB. subtilisDB104. The result shows that the original AQ1 endoxylanase promoter and the signal peptide gave a very high constitutive extracellular expression inE. coliand hence made the production inE. colifeasible.

scholarly journals Effect of Shatt Al-Arab Salinity on the Groundwater of Al-Fao and Al-Siba in Southern Iraq

2021 ◽  
Vol 54 (1E) ◽  
pp. 114-122
Author(s):  
Shahad Abdul-Hameed ◽  
Amal Jabbar Hatem
Keyword(s):  
Electrical Conductivity ◽  
High Salinity ◽  
Saline Water ◽  
Arabian Gulf ◽  
Karun River ◽  
Ph Values ◽  
High Concentrations ◽  
Extent Of Damage ◽  
Southern Iraq ◽  
Very High

This study was conducted to estimate the extent of damage to the population in Basra, southern Iraq, specifically the areas adjacent to the Shatt al-Arab and the Arabian Gulf, which are the Al-Fao district and the Al-Siba region. They are affected by the progression of saline water resulting from the lack of water imports and the Karun River interruption, which led to high concentrations of salts in the Shatt Al-Arabs. Consequently, its effect on lands and all life types in these areas requires correcting a map of the study area to drop the groundwater sites as well as calculate the total dissolved salts, electrical conductivity and pH. This study concluded that the groundwater contains very high percentages of total dissolved solids (2880–10415 mg/l) and electrical conductivity (4450–14190 µs/cm). As it has very high salinity, so it is not suitable for drinking, irrigation, or industry. The values of the pH values (7.1-7.5) indicate that it is a light alkaline.

Microbiology of Commercial Depuration of the Sydney Rock Oyster, Crassostrea commercialis

1984 ◽  
Vol 47 (9) ◽  
pp. 703-706 ◽  
Author(s):  
MICHAEL J. EYLES ◽  
GEORGE R. DAVEY
Keyword(s):  
Vibrio Parahaemolyticus ◽  
Geometric Mean ◽  
Pathogenic Microorganisms ◽  
Purification Process ◽  
E Coli ◽  
Rock Oyster ◽  
Plate Counts ◽  
Low Levels ◽  
High Concentrations ◽  
Pathogenic Vibrios

Paired batches of unpurified and commercially purified oysters from a polluted estuary were examined for a range of indicator and pathogenic microorganisms on 16 occasions over a period of 1 year. Aerobic plate counts of purified oysters (geometric mean of all samples 4.8 × 102/g) were generally lower than those of unpurified oysters (geometric mean of all samples 1.2 × 103/g). Coliforms and Escherichia coli were detected considerably less frequently, and usually at lower levels in purified than in unpurified oysters. Three batches of purified oysters contained unacceptably high concentrations of E. coli. The purification process had little impact on the incidence or concentration of Vibrio parahaemolyticus, which was present at low levels (up to 48/g) in 12 batches of both unpurified and purified oysters. Non-01 serotypes of V. cholerae were also present in purified oysters. Viruses were not detected. In a subsequent survey, 54 oyster samples from 25 different purification plants and 5 estuaries were examined. Twenty one samples contained V. parahaemolyticus at levels up to 48/g and one contained V. cholerae (non-01). Ten samples contained E. coli. The results indicate that small numbers of potentially pathogenic vibrios are frequently a part of the microflora of purified oysters.

scholarly journals Impact of mcr-1 on the Development of High Level Colistin Resistance in Klebsiella pneumoniae and Escherichia coli

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiao-Qing Zhu ◽  
Yi-Yun Liu ◽  
Renjie Wu ◽  
Haoliang Xun ◽  
Jian Sun ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Klebsiella Pneumoniae ◽  
Bacterial Species ◽  
Survival Rates ◽  
Genetic Alterations ◽  
Colistin Resistance ◽  
E Coli ◽  
High Concentrations ◽  
High Level ◽  
The Impact

Plasmid-mediated colistin resistance gene mcr-1 generally confers low-level resistance. The purpose of this study was to investigate the impact of mcr-1 on the development of high-level colistin resistance (HLCR) in Klebsiella pneumoniae and Escherichia coli. In this study, mcr-1-negative K. pneumoniae and E. coli strains and their corresponding mcr-1-positive transformants were used to generate HLCR mutants via multiple passages in the presence of increasing concentrations of colistin. We found that for K. pneumoniae, HLCR mutants with minimum inhibitory concentrations (MICs) of colistin from 64 to 1,024 mg/L were generated. Colistin MICs increased 256- to 4,096-fold for mcr-1-negative K. pneumoniae strains but only 16- to 256-fold for the mcr-1-harboring transformants. For E. coli, colistin MICs increased 4- to 64-folds, but only 2- to 16-fold for their mcr-1-harboring transformants. Notably, mcr-1 improved the survival rates of both E. coli and K. pneumoniae strains when challenged with relatively high concentrations of colistin. In HLCR K. pneumoniae mutants, amino acid alterations predominately occurred in crrB, followed by phoQ, crrA, pmrB, mgrB, and phoP, while in E. coli mutants, genetic alterations were mostly occurred in pmrB and phoQ. Additionally, growth rate analyses showed that the coexistence of mcr-1 and chromosomal mutations imposed a fitness burden on HLCR mutants of K. pneumoniae. In conclusion, HLCR was more likely to occur in K. pneumoniae strains than E. coli strains when exposed to colistin. The mcr-1 gene could improve the survival rates of strains of both bacterial species but could not facilitate the evolution of high-level colistin resistance.

scholarly journals Studying the personality traits of students within the framework of the poles splitting of the cognitive style analyticity/synthetic

2021 ◽  
Vol 27 (1) ◽  
pp. 59-64
Author(s):  
Svetlana A. Dupina
Keyword(s):  
Personality Traits ◽  
Cognitive Style ◽  
Trait Anxiety ◽  
State Trait Anxiety Inventory ◽  
Research Results ◽  
Empathy Development ◽  
Low Levels ◽  
High Level ◽  
Very High

This article examines the problem of studying anxiety and empathy within the framework of the splitting of the poles of the cognitive style of analyticity/synthetics in subjects aged 17-18. The study was carried out using the following methods – “Free sortingˮ by Riley W. Gardner modified by Voldemar Kolga, “Diagnostics of the level of empathyˮ by Il’dar Yusupov, “State-Trait Anxiety Inventoryˮ by Charles Donald Spielberger and Juri Hanin. The study involved 80 students. Using the methodology “Free sortingˮ by R.W. Gardner, modified by V.A. Kolga, the following groups were identified in the sample of subjects: synthetics/categorisers, synthetics/globalists, analysts/differentiators and analysts/detailisers. Diagnostics according to the methodology “State-Trait Anxiety Inventory” by Ch.D. Spielberger and J. Hanin made it possible to identify high, medium, and low levels of anxiety. Analysis of the research results using the methodology “Diagnostics of the level of empathyˮ by I.M. Yusupov determined the presence in the sample of students of very high, high, medium and low levels of development of empathy. The group of synthetics/categorisers and analysts/differentiators were distinguished by low and medium levels of anxiety, high and medium levels of empathy development. The group of synthetics/globalists and analysts/detailisers was characterised by a high level of anxiety, low and medium levels of development of empathy.

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