Scholarly

Characterization of Silica Nanoparticles in Interaction with Escherichia coli Bacteria

Year: 2013 Volume: 7 Issue: 7 536 - 542 Pages

Abstract: The objective of the present investigation was to evaluate the morphology of Escherchia coli bacteria in interaction with SiO2 nanoparticles. This study was made by atomic force microscopy and quartz crystal microbalance using SiO2 nanoparticles with 10nm, 50nm and 100nm diameter and bacteria immobilized on polyelectrolyte multilayer films obtained by spin coating or by “layer by layer” (LbL) method.

Construction of Recombinant E.coli Expressing Fusion Protein to Produce 1,3-Propanediol

Year: 2011 Volume: 5 Issue: 4 217 - 223 Pages

Abstract: In this study, a synthetic pathway was created by assembling genes from Clostridium butyricum and Escherichia coli in different combinations. Among the genes were dhaB1 and dhaB2 from C. butyricum VPI1718 coding for glycerol dehydratase (GDHt) and its activator (GDHtAc), respectively, involved in the conversion of glycerol to 3-hydroxypropionaldehyde (3-HPA). The yqhD gene from E.coli BL21 was also included which codes for an NADPHdependent 1,3-propanediol oxidoreductase isoenzyme (PDORI) reducing 3-HPA to 1,3-propanediol (1,3-PD). Molecular modeling analysis indicated that the conformation of fusion protein of YQHD and DHAB1 was favorable for direct molecular channeling of the intermediate 3-HPA. According to the simulation results, the yqhD and dhaB1 gene were assembled in the upstream of dhaB2 to express a fusion protein, yielding the recombinant strain E. coliBL21 (DE3)//pET22b+::yqhD-dhaB1_dhaB2 (strain BP41Y3). Strain BP41Y3 gave 10-fold higher 1,3-PD concentration than E. coliBL21 (DE3)//pET22b+::yqhD-dhaB1_dhaB2 (strain BP31Y2) expressing the recombinant enzymes simultaneously but in a non-fusion mode. This is the first report using a gene fusion approach to enhance the biological conversion of glycerol to the value added compound 1,3- PD.

Synthesis of Silver Nanoparticles by Chemical Reduction Method and Their Antibacterial Activity

Year: 2008 Volume: 2 Issue: 7 107 - 114 Pages

Abstract: Silver nanoparticles were prepared by chemical reduction method. Silver nitrate was taken as the metal precursor and hydrazine hydrate as a reducing agent. The formation of the silver nanoparticles was monitored using UV-Vis absorption spectroscopy. The UV-Vis spectroscopy revealed the formation of silver nanopart├¡cles by exhibing the typical surface plasmon absorption maxima at 418-420 nm from the UV–Vis spectrum. Comparison of theoretical (Mie light scattering theory) and experimental results showed that diameter of silver nanoparticles in colloidal solution is about 60 nm. We have used energy-dispersive spectroscopy (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and, UV–Vis spectroscopy to characterize the nanoparticles obtained. The energy-dispersive spectroscopy (EDX) of the nanoparticles dispersion confirmed the presence of elemental silver signal no peaks of other impurity were detected. The average size and morphology of silver nanoparticles were determined by transmission electron microscopy (TEM). TEM photographs indicate that the nanopowders consist of well dispersed agglomerates of grains with a narrow size distribution (40 and 60 nm), whereas the radius of the individual particles are between 10 and 20 nm. The synthesized nanoparticles have been structurally characterized by X-ray diffraction and transmission high-energy electron diffraction (HEED). The peaks in the XRD pattern are in good agreement with the standard values of the face-centered-cubic form of metallic silver (ICCD-JCPDS card no. 4-0787) and no peaks of other impurity crystalline phases were detected. Additionally, the antibacterial activity of the nanopart├¡culas dispersion was measured by Kirby-Bauer method. The nanoparticles of silver showed high antimicrobial and bactericidal activity against gram positive bacteria such as Escherichia Coli, Pseudimonas aureginosa and staphylococcus aureus which is a highly methicillin resistant strain.

Novel Inhibitor of E. coli DNA Adenine Methyltransferase (Ecodam)

Year: 2013 Volume: 7 Issue: 1 32 - 34 Pages

Abstract: EcoDam is an adenine-N6 DNA methyltransferase that methylates the GATC sites in the Escherichia coli genome. DNA-adenine methylation is not present in higher eukaryotes including humans. These observations raise the possibility that dam inhibitors may be used as anti-microbial agents. Polyphosphate (Poly(P)) is an important metabolite and signaling molecule in prokaryotes and eukaryotes. Here, by using gel retardation experiments to investigate the competition of DNA binding by EcoDam in the presence of polyphosphate, we found that Poly (P) strongly interferes with DNA binding by EcoDam, while same concentration of monophosphate does not. In addition, we demonstrated that Poly (P) binding inhibits the activity of EcoDam and our results suggest that Poly (P) led to strong inhibition of the EcoDam catalytic activity, while monophosphate had only moderate effect.

Antibacterial Capacity of Plumeria alba Petals

Year: 2010 Volume: 4 Issue: 8 324 - 327 Pages

Abstract: Antibacterial activity of Plumeria alba (Frangipani) petals methanolic extracts were evaluated against Escherichia coli, Proteus vulgaris,Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus saprophyticus, Enterococcus faecalis and Serratia marcescens by using disk diffusion method. Concentration extracts (80 %) showed the highest inhibition zone towards Escherichia coli (14.3 mm). Frangipani extract also showed high antibacterial activity against Staphylococcus saprophyticus, Proteus vulgaris and Serratia marcescens, but not more than the zones of the positive control used. Comparison between two broad specrum antibiotics to frangipani extracts showed that the 80 % concentration extracts produce the same zone of inhibition as Streptomycin. Frangipani extracts showed no bacterial activity towards Klebsiella pneumoniae, Pseudomonas aeruginosa and Enterococcus faecalis. There are differences in the sensitivity of different bacteria to frangipani extracts, suggesting that frangipani-s potency varies between these bacteria. The present results indicate that frangipani showed significant antibacterial activity especially to Escherichia coli.

X-ray Crystallographic Analysis of MinC N-Terminal Domain from Escherichia coli

Year: 2010 Volume: 4 Issue: 8 560 - 563 Pages

Abstract: MinC plays an important role in bacterial cell division system by inhibiting FtsZ assembly. However, the molecular mechanism of the action is poorly understood. E. coli MinC Nterminus domain was purified and crystallized using 1.4 M sodium citrate pH 6.5 as a precipitant. X-ray diffraction data was collected and processed to 2.3 Å from a native crystal. The crystal belonged to space group P212121, with the unit cell parameters a = 52.7, b = 54.0, c = 64.7 Å. Assuming the presence of two molecules in the asymmetric unit, the Matthews coefficient value is 1.94 Å3 Da-1, which corresponds to a solvent content of 36.5%. The overall structure of MinCN is observed as a dimer form through anti-parallel ß-strand interaction.

Antioxydant and Antibacterial Activity of Alkaloids and Terpenes Extracts from Euphorbia granulata

Year: 2013 Volume: 7 Issue: 3 186 - 189 Pages

Abstract: In order to enhance the knowledge of certain phytochemical Algerian plants that are widely used in traditional medicine and to exploit their therapeutic potential in modern medicine, we have done a specific extraction of terpenes and alkaloids from the leaves of Euphorbia granulata to evaluate the antioxidant and antibacterial activity of this extracts. After the extraction it was found that the terpene extract gave the highest yield 59.72% compared with alkaloids extracts. The disc diffusion method was used to determine the antibacterial activity against different bacterial strains: Escherichia coli (ATCC25922), Pseudomonas aeruginosa (ATCC27853) and Staphylococcus aureus (ATCC25923). All extracts have shown inhibition of growth bacteria. The different zones of inhibition have varied from (7 -10 mm) according to the concentrations of extract used. Testing the antiradical activity on DPPH-TLC plates indicated the presence of substances that have potent anti-free radical. As against, the BC-TLC revealed that only terpenes extract which was reacted positively. These results can validate the importance of Euphorbia granulata in traditional medicine.

Effectiveness of Moringa oleifera Coagulant Protein as Natural Coagulant aid in Removal of Turbidity and Bacteria from Turbid Waters

Year: 2010 Volume: 4 Issue: 7 281 - 283 Pages

Abstract: Coagulation of water involves the use of coagulating agents to bring the suspended matter in the raw water together for settling and the filtration stage. Present study is aimed to examine the effects of aluminum sulfate as coagulant in conjunction with Moringa Oleifera Coagulant Protein as coagulant aid on turbidity, hardness, and bacteria in turbid water. A conventional jar test apparatus was employed for the tests. The best removal was observed at a pH of 7 to 7.5 for all turbidities. Turbidity removal efficiency was resulted between % 80 to % 99 by Moringa Oleifera Coagulant Protein as coagulant aid. Dosage of coagulant and coagulant aid decreased with increasing turbidity. In addition, Moringa Oleifera Coagulant Protein significantly has reduced the required dosage of primary coagulant. Residual Al+3 in treated water were less than 0.2 mg/l and meets the environmental protection agency guidelines. The results showed that turbidity reduction of % 85.9- % 98 paralleled by a primary Escherichia coli reduction of 1-3 log units (99.2 – 99.97%) was obtained within the first 1 to 2 h of treatment. In conclusions, Moringa Oleifera Coagulant Protein as coagulant aid can be used for drinking water treatment without the risk of organic or nutrient release. We demonstrated that optimal design method is an efficient approach for optimization of coagulation-flocculation process and appropriate for raw water treatment.

Incidence of Pathogenic Bacteria in Cakes and Tarts Displayed for Sale in Tripoli, Libya

Year: 2013 Volume: 7 Issue: 3 181 - 185 Pages

Abstract: This study was conducted to investigate the incidence of pathogenic bacteria: Salmonella, Shigella, Escherichia coli O157 and Staphylococcus aureus in cakes and tarts collected from thirtyfive confectionery producing and selling premises located within Tripoli city, Libya. The results revealed an incidence of S. aureus with 94.4 and 48.0 %, E. coli O157 with 14.7 and 4.0 % and Salmonella sp. with 5.9 and 8.0 % in cakes and tarts samples respectively; while Shigella was not detected in all samples. In order to determine the source of these pathogenic bacteria, cotton swabs were taken from the hands of workers on the production line, the surfaces of preparation tables and cream whipping instruments. The results showed that the cotton swabs obtained from the hands of workers contained S. aureus and Salmonella sp. with an incidence of 42.9 and 2.9 %, the cotton swabs obtained from the surfaces of preparation tables 22.9 and 2.9 % and the cotton swabs obtained from the cream whipping instruments 14.3 and 0.0 % respectively; while E. coli O157 and Shigella sp. were not detected in all swabs. Additionally, other bacteria were isolated from the hands of workers and the Surfaces of producing equipments included: Aeromonas sp., Pseudomonas sp., E. coli, Klebsiella sp., Enterobacter sp., Citrobacter sp., Proteus sp., Serratia sp. and Acinetobacter sp. These results indicate that some of the cakes and tarts might pose threat to consumer's health. Meanwhile, occurrences of pathogenic bacteria on the hands of those who are working in production line and the surfaces of equipments reflect poor hygienic practices at most confectionery premises examined in this study. Thus, firm and continuous surveillance of these premises is needed to insure the consumer's health and safety.

Keywords:
Pathogenic bacteria
Cakes
Tarts
Confectionery producing and selling premises.

In Vitro Antibacterial and Antifungal Effects of a 30 kDa D-Galactoside-Specific Lectin from the Demosponge, Halichondria okadai

Year: 2010 Volume: 4 Issue: 1 17 - 23 Pages

Abstract: The present study has been taken to explore the screening of in vitro antimicrobial activities of D-galactose-binding sponge lectin (HOL-30). HOL-30 was purified from the marine demosponge Halichondria okadai by affinity chromatography. The molecular mass of the lectin was determined to be 30 kDa with a single polypeptide by SDS-PAGE under non-reducing and reducing conditions. HOL-30 agglutinated trypsinized and glutaraldehydefixed rabbit and human erythrocytes with preference for type O erythrocytes. The lectin was subjected to evaluation for inhibition of microbial growth by the disc diffusion method against eleven human pathogenic gram-positive and gram-negative bacteria. The lectin exhibited strong antibacterial activity against gram-positive bacteria, such as Bacillus megaterium and Bacillus subtilis. However, it did not affect against gram-negative bacteria such as Salmonella typhi and Escherichia coli. The largest zone of inhibition was recorded of Bacillus megaterium (12 in diameter) and Bacillus subtilis (10 mm in diameter) at a concentration of the lectin (250 μg/disc). On the other hand, the antifungal activity of the lectin was investigated against six phytopathogenic fungi based on food poisoning technique. The lectin has shown maximum inhibition (22.83%) of mycelial growth of Botrydiplodia theobromae at a concentration of 100 μg/mL media. These findings indicate that the lectin may be of importance to clinical microbiology and have therapeutic applications.

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