Abstract

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Silver nanoparticles (AgNPs) was synthesized using a combination of aqueous extract of Croton zambesicus and silver nitrate (AgNO3) solution to obtain various concentrations of 100mg/ml, 200mg/ml, 300mg/ml and 400mg/ml at 10mM. Characterization of the synthesized silver nanoparticle was done by UV-visible spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). Antimicrobial activity against four bacterial isolates was determined by standard method of agar-well diffusion assay. The activity of two standard antibiotics was compared with the AgNPs of C. zambesicus using the disc diffusion method. The Minimum Inhibitory Concentration (MIC) was achieved using microbroth dilution technique. Test tubes that showed low turbidity in the MIC assays were reinoculated on sterile agar plates and this was taken as Minimum Inhibitory Concentration (MBC). The presence of phytochemical constituent was examined using standard methods. The total yield of the AgNPs of the plant extract was 10.94g. The characterization by UV-visible revealed that at a wavelength of 429.0nm the particle has peak absorbance of 2.003, while the FTIR showed the presence of five (5) functional groupsE. coli demonstrated reduction in activity as concentration increased with zone diameter of 24mm at 100mg/ml and 10mm at 400mg/ml. The analysis of MIC and MBC revealed inhibitory and bactericidal effects at the same concentration of 30mg/ml. The mode of action of the AgNPs at 100mg/ml showed a total cell lysis of all test isolates. Following the results of the phytochemical analysis, the presence of six phytochemicals were observed. It is evident from this study that AgNPs synthesized from extract of leaf of C. zambesicus is a very effective antibacterial agent that can compare favourably with conventional antibiotics, hence considering it as an alternative in the elimination of the tested isolates and infections caused by them.

Abstract

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Phylogenetic analysis of sulphidogenic bacterial isolates from Nigerian Bonny light crude oil and its produce water samples was carried out following preliminary detection of the bacterial species. Samples were enriched in mixed carbon postgate’s (MCP) medium and incubated at 55 ºC for 28 days. DNA was extracted from isolated culture and amplified by Polymerase Chain Reaction (PCR) using 16S rRNA eubacterial primers with a GC–clamp. Successful amplification was confirmed by ethidium bromide fluorescence in 1 % agarose gelafter agarose gel electrophoresis. PCR-amplified DNA was separated by Denaturing Gradient Gel Electrophoresis (DGGE) analysis, to show the relationship between samples based on their GC content. Following successful DGGE analysis, DGGE bands were excised, purified and sequenced to display sequence homology and affiliation to related genera of sulphide producers. The DGGE products sequencing was successful, displaying 98 % and 99 % similarity and homology to Petrotogamexicana (AY125964.1) and Petrotogaolearia (AJ311703.1) respectively. Phylogenetic analysis showed a relationship between the sulphidogenic bacteria with other members of the Thermotogales.

Abstract

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The prevalence of bacteria causing UTI in diabetic patients, as well as their susceptibility to commonly used antibiotics was investigated in Benin City. Bacteriological analysis involved standard biochemical tests and comparison of isolates’ characteristics with known taxa. Species isolated from the urine samples analysed were Escherichia coli, Staphylococcus aureus, Staphylococcus saprophyticus, Proteus mirabilis and Pseudomonas aeruginosa. Gram-negative isolates had a prevalence of 60 %, while Gram-positive isolates had 40 %. E. coli were found to be the most prevalence (44.4 %), while the least prevalent were P. aeruginosa(11.1 %),S. aureus(11.1 %) and S. saprophyticus (11.1 %). Isolates were found to be more in females than males. Three out of the six male diabetics sampled had uropathogens, while six out of the fifteen female diabetics sampled had uropathogens. Susceptibility tests were performed by Bauer-Kirby disc-diffusion method with standard antibiotics. The results were expressed as susceptible or resistant. All the isolates were found to be susceptible to ciprofloxacin and gentamicin. They were also found to be multi-drug resistant. This study showed that diabetic patients had increased risk of urinary tract infections due to the presence of uropathogens.

Abstract

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Moringa oleiferahas been found very useful in a lot of health related problems owing to its medicinal components and values, these has led to research on its antibacterial activity against food borne pathogens. Aqueous and acetone extracts of Moringa oleifera seed kernel and leaf were evaluated for antibacterial activity against Bacillus cereus, Staphylococcus aureus and Escherichia coli isolated from raw cow milk. The antibacterial assay was carried out at concentrations of 250, 125, 62.5 and 31.25mg/ml using modified agar well diffusion method. Aqueous extract inhibited the growth of test isolates at varying degrees. Aqueous extract of seed kernel was highly inhibitory on Staphylococcus aureus with a zone of inhibition (23.33±1.20mm) at concentration of 250mg/ml. Minimum Inhibitory Concentration showed that both extracts inhibited the growth of Bacillus cereus, Staphylococcus aureus and Escherichia coli at concentrations ranging from 125 to 21.25mg/ml. The antibacterial effect of standard antibiotics was performed and it was observed that Gentamycin inhibited growth of the three test isolates. Preliminary phytochemical screening revealed the presence of alkaloids, flavonoids, steroids, saponin, tannin, phenols, glycosides and carbohydrates compound in the extracts. From the present study, Moringa oleifera seed kernel and leaf can be a promising source of phytochemical components and further studies is therefore recommended.

Abstract

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Silver nanoparticles (SNPs) are nanoparticles of silver that are in the range of 1.0 and 100nm in size. They have unique antimicrobial properties which help in water sanitation and medical industries, but their potentials in agriculture have not been utilized. This study was conducted to investigate the effectiveness of SNPs synthesized using different concentrations of bitter leaf (Vernonia amygdalina) extracts in inhibiting the growth of three plant pathogenic fungi; Fusarium oxysporum, F. solani and Cercospora canescens isolated from diseased plants and identified using molecular method. Synthesized SNPs were characterized using UV-Vis absorption spectroscopy. The antifungal activity of SNPs synthesized at 0, 2, 5 and 10 mins using 0.10g/ml and 0.20g/ml of bitter leaf extracts were evaluated on the basis of colony formation by in-vitro assays. UV-visible spectroscopic analyses revealed rapid reduction of silver ions (Ag+) by bitter leaf extracts where surface Plasmon absorption maxima were observed from the UV-vis spectra. The growth of pathogenic fungi on agar plates were significantly decreased or totally inhibited by treatment with the SNPs depending on the concentrations of the plant extracts and the time of reaction. SNPs synthesized with 0.20g/ml of the extract for 10 mins completely inhibited the growth of the tested fungal pathogens while other SNPs significantly reduced their growth (60 – 90% reduction). The results of this study indicated that the silver nanoparticles synthesized using bitter leaf extracts have potentials to be used as control agents against fungal plant diseases to replace the use of chemical fungicides.

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Optimization of fermentation process for 72 h was carried out to determine the effect of pH (3 – 8), temperature (30°C – 50°C) and agitation rate (200 rpm – 500 rpm) on bioethanol production and microbial count using cassava variety samples. Bioethanol yield and microbial count were highest at pH 6, temperature 35°C and agitation rate of 300 rpm. The bacterial species had highest population counts of 5. 21 x 105 cfu/g at pH 6, 4.62 x 105 cfu/g at temperature 35°C and 4.84 x 105 cfu/g at pH 6, 3.94 x 105 cfu/g at temperature 35 °C for sweet and bitter cassava varieties respectively. The fungal species had highest counts of 5.60 x 104 cfu/g at pH 6, 2.53 x 104 cfu/g at temperature 35°C and 5.20 x 104 cfu/g at pH 6, 2.11 x 104 cfu/g at temperature 35°C for sweet and bitter cassava varieties. Bioethanol yield was 56% and 44% resulting in a significant increase of 75% and 63% for the sweet and bitter cassava varieties respectively. The optimization of the fermentation process yielded maximum bioethanol and also detoxified the cassava processing wastes which are environmental pollutants.