scholarly journals Induction of complement sensitivity in Escherichia coli by citric acid and low pH

2001 ◽  
Vol 90 (5) ◽  
pp. 771-778 ◽  
Author(s):  
C. Ocana-Morgner ◽  
J.R. Dankert
Keyword(s):  
Escherichia Coli ◽  
Citric Acid ◽  
Low Ph

Microbial Quality of Hoummos (Chickpea Dip) Commercially Produced in Jordan

1994 ◽  
Vol 57 (5) ◽  
pp. 431-435 ◽  
Author(s):  
MOHAMMED I. YAMANI ◽  
BASIM A. AL-DABABSEH
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Low Ph ◽  
Plate Count ◽  
Microbial Quality ◽  
Aerobic Plate Count ◽  
And Staphylococcus Aureus ◽  
Reference Samples ◽  
Hygienic Conditions

Sixty samples of fresh hoummos (chickpea dip) from 15 restaurants were examined in winter and summer to find out numbers and types of microorganisms present. Five reference samples, produced by the investigators under hygienic conditions, were examined for comparison. The microbial load of commercial hoummos was high, and spherical lactic acid bacteria (LAB) belonging to Lactococcus, Enterococcus and Leuconostoc were the predominant microorganisms. The means of the aerobic plate count (APC) and the counts of LAB and coliforms (1.9 × 108, 1.6 × 108 and 2.9 × 105/g, respectively) in summer samples were significantly higher (p < 0.05) than the averages of the same counts in winter samples (2.7 × 107, 1.6 × 107 and 2.2 × 103/g). The average summer and winter yeast counts were 4.2 × 104 and 1.5 × 104g, respectively. In reference samples of hoummos, APC and LAB counts were < 103/g, while the coliform and yeast counts were < 10/g and 102/g, respectively, indicating lack of hygienic practices during the production of commercial hoummos. Salmonella was not detected in any sample, and Escherichia coli and Staphylococcus aureus counts of all samples were < 10/g. The relatively low pH of hoummos (the average pH of all samples was 5.1) and the rapid growth of LAB, possibly accompanied by production of inhibitory substances, may explain the predominance of these bacteria, and could have contributed to the absence of the pathogens examined.

scholarly journals Characterization and antimicrobial activity of vaginal lactobacillus isolate

2011 ◽  
Vol 63 (1) ◽  
pp. 29-35 ◽  
Author(s):  
Gordana Zavisic ◽  
Zeljka Radulovic ◽  
Valentina Vranic ◽  
Jelena Begovic ◽  
L. Topisirovic ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Activity ◽  
Survival Rate ◽  
Bile Salts ◽  
Antimicrobial Effect ◽  
Low Ph ◽  
Probiotic Potential ◽  
Pathogenic Escherichia Coli

The aim of this study was to investigate the probiotic potential of bacteriocin-producing lactobacilli strain Lactobacillus plantarum G2 isolated from the vaginal mucus of healthy women. The antimicrobial effect of G2 was confirmed in the mixed culture with pathogenic Escherichia coli, Staphylococcus aureus, Salmonella abony and Pseudomonas aeruginosa, while bacteriocine activity was detected against S. aureus and S. abony only. The strain showed an excellent survival rate in low pH and in the presence of bile salts. The percentage of adhered cells of L. plantarum G2 to hexadecane was 63.85?2.0 indicating the intermediate hydrophobicity.

scholarly journals Enhanced citric acid biosynthesis in Pseudomonas fluorescens ATCC 13525 by overexpression of the Escherichia coli citrate synthase gene

Microbiology ◽  
2009 ◽  
Vol 155 (8) ◽  
pp. 2620-2629 ◽  
Author(s):  
Aditi D. Buch ◽  
G. Archana ◽  
G. Naresh Kumar
Keyword(s):  
Escherichia Coli ◽  
Citric Acid ◽  
Acid Secretion ◽  
Pseudomonas Fluorescens ◽  
Phosphoenolpyruvate Carboxylase ◽  
Citrate Synthase ◽  
Acid Biosynthesis ◽  
Acid Yield ◽  
Glucose Catabolism ◽  
Citric Acid Biosynthesis

Citric acid secretion by fluorescent pseudomonads has a distinct significance in microbial phosphate solubilization. The role of citrate synthase in citric acid biosynthesis and glucose catabolism in pseudomonads was investigated by overexpressing the Escherichia coli citrate synthase (gltA) gene in Pseudomonas fluorescens ATCC 13525. The resultant ∼2-fold increase in citrate synthase activity in the gltA-overexpressing strain Pf(pAB7) enhanced the intracellular and extracellular citric acid yields during the stationary phase, by about 2- and 26-fold, respectively, as compared to the control, without affecting the growth rate, glucose depletion rate or biomass yield. Decreased glucose consumption was paralleled by increased gluconic acid production due to an increase in glucose dehydrogenase activity. While the extracellular acetic acid yield increased in Pf(pAB7), pyruvic acid secretion decreased, correlating with an increase in pyruvate carboxylase activity and suggesting an increased demand for the anabolic precursor oxaloacetate. Activities of two other key enzymes, glucose-6-phosphate dehydrogenase and isocitrate dehydrogenase, remained unaltered, and the contribution of phosphoenolpyruvate carboxylase and isocitrate lyase to glucose catabolism was negligible. Strain Pf(pAB7) demonstrated an enhanced phosphate-solubilizing ability compared to the control. Co-expression of the Synechococcus elongatus PCC 6301 phosphoenolpyruvate carboxylase and E. coli gltA genes in P. fluorescens ATCC 13525, so as to supplement oxaloacetate for citrate biosynthesis, neither significantly affected citrate biosynthesis nor caused any change in the other physiological and biochemical parameters measured, despite approximately 1.3- and 5-fold increases in citrate synthase and phosphoenolpyruvate carboxylase activities, respectively. Thus, our results demonstrate that citrate synthase is rate-limiting in enhancing citrate biosynthesis in P. fluorescens ATCC 13525. Significantly low extracellular citrate levels as compared to the intracellular levels in Pf(pAB7) suggested a probable limitation of efficient citrate transport.

Formate and potassium ions affect Escherichia coli proton ATPase activity at low pH during mixed carbon fermentation

IUBMB Life ◽  
2020 ◽  
Vol 72 (5) ◽  
pp. 915-921 ◽  
Author(s):  
Heghine Gevorgyan ◽  
Armen Trchounian ◽  
Karen Trchounian
Keyword(s):  
Escherichia Coli ◽  
Atpase Activity ◽  
Low Ph ◽  
Potassium Ions ◽  
Proton Atpase

Influence of Sodium Chloride on Growth of Lactic Acid Bacteria and Subsequent Destruction of Escherichia coli O157:H7 during Processing of Lebanon Bologna

2001 ◽  
Vol 64 (8) ◽  
pp. 1145-1150 ◽  
Author(s):  
NAVEEN CHIKTHIMMAH ◽  
RAMASWAMY C. ANANTHESWARAN ◽  
ROBERT F. ROBERTS ◽  
EDWARD W. MILLS ◽  
STEPHEN J. KNABEL
Keyword(s):  
Escherichia Coli ◽  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Low Ph ◽  
Escherichia Coli O157 ◽  
Quality Changes ◽  
E Coli ◽  
Fermented Product ◽  
Nacl Concentration ◽  
Different Levels

Due to undesirable quality changes, Lebanon bologna is often processed at temperatures that do not exceed 48.8°C (120°F). Therefore, it is important to study parameters that influence the destruction of Escherichia coli O157:H7 in Lebanon bologna. The objective of the present study was to determine the influence of curing salts (NaCl and NaNO2) on the destruction of E. coli O157:H7 during Lebanon bologna processing. Fermentation to pH 4.7 at 37.7°C reduced populations of E. coli O157:H7 by approximately 0.3 log10, either in the presence or absence of curing salts. Subsequent destruction of E. coli O157:H7 during heating of fermented product to 46.1°C was significantly reduced by the presence of 3.5% NaCl and 156 ppm NaNO2, compared to product without curing salts (P < 0.01). The presence of a higher level of NaCl (5%) in Lebanon bologna inhibited the growth of lactic acid bacteria (LAB), which yielded product with higher pH (~5.0) and significantly reduced the destruction of E. coli O157:H7 even further (P < 0.05). Lower concentrations of NaCl (0, 2.5%) yielded Lebanon bologna with higher LAB counts and lower pHs, compared to product with 5% NaCl. When lactic acid was used to adjust pH in product containing different levels of NaCl, it was determined that low pH was directly influencing destruction of E. coli O157:H7, not NaCl concentration.

10-Minute Assay for Detecting Escherichia coli O157:H7 in Ground Beef Samples Using Piezoelectric-Excited Millimeter-Size Cantilever Sensors

2007 ◽  
Vol 70 (7) ◽  
pp. 1670-1677 ◽  
Author(s):  
DAVID MARALDO ◽  
RAJ MUTHARASAN
Keyword(s):  
Escherichia Coli ◽  
Sample Preparation ◽  
Ground Beef ◽  
Low Ph ◽  
Frequency Change ◽  
Escherichia Coli O157 ◽  
Label Free ◽  
Cantilever Sensors ◽  
Ph Buffer ◽  
Phosphate Buffered Saline

We detected Escherichia coli O157:H7 (EC) at approximately 10 cells per ml in spiked ground beef samples in 10 min using piezoelectric-excited millimeter-size cantilever (PEMC) sensors. The composite PEMC sensors have a sensing area of 2mm2 and are prepared by immobilizing a polyclonal antibody specific to EC on the sensing surface. Ground beef (2.5 g) was spiked with EC at 10 to 10,000 cells per ml in phosphate-buffered saline (PBS). One milliliter of supernatant was removed from the blended samples and used to perform the detection experiments. The total resonant frequency change obtained for the inoculated samples was 138 ± 9, 735 ± 23, 2,603 ± 51, and 7,184 ± 606 Hz, corresponding to EC concentrations of 10, 100, 1,000, and 10,000 cells per ml, respectively. EC was detected in the sample solution within the first 10 min. The responses of the sensor to positive, negative, and buffer controls were 36 ± 6, 27 ± 2, and 2 ± 7 Hz, respectively. Verification of EC attachment was confirmed by low-pH buffer release (PBS-HCl, pH 2.2), microscopy, and second antibody EC binding postdetection. The results indicate that PEMC sensors can reliably detect EC at less than 10 cells per ml in 10 min without sample preparation and with label-free reagents.

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