Studies on the surface plate method of counting bacteria

1971 ◽  
Vol 17 (7) ◽  
pp. 943-946 ◽  
Author(s):  
D. S. Clark
Keyword(s):  
Escherichia Coli ◽  
Weight Loss ◽  
Pseudomonas Fluorescens ◽  
Good Recovery ◽  
Plate Method ◽  
Spreading Time ◽  
Inoculum Volume ◽  
Time Required ◽  
Surface Plate

A study of plate preparation, inoculum volume, and technique of spreading in the surface plate method showed that predrying plates to a weight loss of 3–4 g/15-ml plate allowed the use of inoculum volumes of up to 1 ml without affecting recovery of bacteria. Satisfactory drying was achieved at 24–50 °C with the plates positioned upside down separately or in stacks. Equally good recovery of bacteria was obtained either by spreading the inoculum until it had been completely absorbed, or by spreading it for only 15 s and waiting for absorption and evaporation of excess liquid before inverting the plate. The former technique was limited to about 0.5 ml of inoculum because of the length of the spreading time required for volumes greater than this, whereas the latter method was satisfactory for volumes up to at least 1 ml as shown in recovery tests with Escherichia coli and Pseudomonas fluorescens.

Finite Element Model to Predict the Bioconversion Rate of Glucose to Fructose using Escherichia coli K12 for Sugar Production from Date

2015 ◽  
Vol 11 (1) ◽  
pp. 105-113 ◽  
Author(s):  
Maher Trigui ◽  
Karim Gabsi ◽  
Walid Zneti ◽  
Suzelle Barrington ◽  
Ahmed Noureddine Helal
Keyword(s):  
Escherichia Coli ◽  
Induction Time ◽  
Volume Fraction ◽  
Element Model ◽  
Initial Concentration ◽  
Computational Fluids Dynamics ◽  
Date Syrup ◽  
Computational Fluids ◽  
Two Phases ◽  
Inoculum Volume

Abstract In this study, Bioconversion process of glucose to fructose from date syrup using Escherichia coli K12 is modeled using a commercial computational fluids dynamics (CFD) code fluent FLUENT 6.3.23 [8] which we implemented a user-defined functions (UDF) to simulate the interrelationships at play between various phases. A two phases CFD model was developed using an Eulerian – Eulerian approach to calculate the fructose volume fraction produced during time. The bioconversion process was studied as function of three initial concentration of glucose (0.14, 0.242 and 0.463gL–1), three induction time (60, 120 and 180 mn) and three inoculum volume (100, 120 and 150mL). The numerical results are compared with experimental data for bioconversion rate and show good agreement (R2= 0.894). The optimal condition of diffusion was obtained by applying an initial concentration of glucose less than 0.2gL–1 and induction time great than 100 minutes.

scholarly journals Encapsulation of bacteriophage cocktail into chitosan for the treatment of bacterial diarrhea

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Golnar Rahimzadeh ◽  
Majid Saeedi ◽  
Mahmood Moosazadeh ◽  
Seyyed Mohammad Hassan Hashemi ◽  
Amirhossein Babaei ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Weight Loss ◽  
Biocontrol Agent ◽  
Shigella Flexneri ◽  
Treated Group ◽  
Therapeutic Effectiveness ◽  
Gastrointestinal Infection ◽  
Weight Changes ◽  
Gastrointestinal Infections ◽  
Lower Group

AbstractThe therapeutic effectiveness of a chitosan encapsulated bacteriophage cocktail as a smart biocontrol agent was evaluated in this study to be used as a preventative and treatment option for gastrointestinal infections. To evaluate the effect of the bacteriophage formulation on the treatment of gastrointestinal infection, rats were infected with Salmonella enterica, Shigella flexneri, and Escherichia coli. The rats were weighed and their stools cultured. The results showed that the group which had the chitosan encapsulated bacteriophage cocktail did not lose weight after 3 days and had significantly lower group weight changes. Weight loss was significant in the rats that had cefixime administered instead. Positive cultured stools were reduced after 4 days compared to 2 days in the treated group with the chitosan encapsulated bacteriophage cocktail. The chitosan encapsulated bacteriophage cocktail can therefore be effective in the treatment of gastrointestinal infections.

A modified bioassay for heat-stable Escherichia coli enterotoxin

1977 ◽  
Vol 23 (3) ◽  
pp. 331-336 ◽  
Author(s):  
S. Stavric ◽  
D. Jeffrey
Keyword(s):  
Escherichia Coli ◽  
Body Weight ◽  
Incubation Time ◽  
Evans Blue ◽  
Room Temperature ◽  
Blue Dye ◽  
Evans Blue Dye ◽  
Heat Stable ◽  
Stomach Distention ◽  
Time Required

Infant mice were injected orally with preparations containing Escherichia coli heat-stable enterotoxin (ST) and Evans blue dye, and incubated at 22 °C. With enterotoxin-positive samples, the stomach was distended and contained essentially all of the dye. With enterotoxin-negative samples, the stomach remained normal in size and the dye passed freely into the intestines. The time required to obtain the maximum ratio of gut weight to body weight varied from 30 to 90 min and was dependent upon the concentration of enterotoxin. Heat-labile enterotoxin (LT) had no effect during this period.Based on these findings, the mouse incubation time was reduced from 4 h to 90 min, and the heating of test samples was retained only for confirmation of ST. The location of the dye and stomach distention served as an indicator of positive responses to ST. Incubation of the mice at room temperature (22 °C) was found satisfactory.

scholarly journals Antifungal and Antibacterial Activities of Apple Vinegar of Different Cultivars

2021 ◽  
Vol 2021 ◽  
pp. 1-6
Author(s):  
Driss Ousaaid ◽  
Hassan Laaroussi ◽  
Meryem Bakour ◽  
Hayat Ennaji ◽  
Badiaa Lyoussi ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Total Phenolic Content ◽  
Phenolic Content ◽  
Antimicrobial Effect ◽  
Antibacterial Activities ◽  
Antimicrobial Activities ◽  
Total Phenolic ◽  
Plate Method ◽  
Golden Delicious ◽  
Pathogenic Microbes

This study was designed to assess the antimicrobial potencies of apple vinegar against pathogenic microbes. The acidity and total phenolic content were carried out by titration with NaOH 0.1 N and the Folin–Ciocalteu method, respectively, while the spread plate method, agar well diffusion, and MIC assays were used to determine the antimicrobial activities of different vinegar samples. Acidity and phenolic content were dependent on the variety, where the highest values were observed in S2 with 4.02 ± 0.04% and 1.98 ± 0.05 mg GAE/mL for acidity and total phenolic content, respectively. The spread plate method revealed that samples S1 and S2 obtained from the Red delicious variety and Golden delicious variety, respectively, inhibit the growth of all tested strains, while S3 obtained from different varieties and S4 obtained from the Gala royal variety inhibit only two microbes (Escherichia coli and Vibrio cholerae). Sample S1 presented moderate antimicrobial effect against all examined strains with a diameter of inhibition ranging from 11 ± 0.7 to 19 ± 0.5 mm and with MIC values ranging between 1/2 and 1/100. The findings of the current study confirm the usefulness of apple vinegar as a natural sanitizer that inhibits the growth of pathogenic microbes.

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.

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