MALAYSIAN JOURNAL OF MICROBIOLOGY
Aims: Phenolic compounds with various biological activities such as antimicrobial, anti-inflammatory and antioxidative activity are considered as key compounds in propolis. In this study, propolis was obtained in Kuantan, Pahang and is known to be collected from stingless honey bee Trigona thoracica. The objective of this study is to extract propolis using surfactant vitamin E d-α-Tocopheryl polyethylene glycol 1000 succinate (Vitamin E TPGS) and evaluate its antimicrobial activity compared to water and ethanolic propolis extracts.
Methodology and results: Quantitative determinations of phenolic acid and flavonoid such as caffeic acid and quercetin, respectively in propolis extracts were conducted by using High Performance Liquid Chromatography (HPLC). As a result, 70% ethanol extracted propolis (EEP), water extracted propolis (WEP) and 0.02% vitamin E TPGS extracted propolis successfully demonstrate the presence of hydrophilic caffeic acid, while only 70% EEP and 0.02% vitamin E TPGS extracted propolis show the presence of hydrophobic quercetin. Lastly, antimicrobial testing was conducted towards Staphylococcus aureus by using all three different propolis extracts.
Conclusion, significance and impact of study: The results showed EEP and vitamin E TPGS propolis extracts exhibit higher antimicrobial activity compared to the WEP.
Aims: Water is described as safe and wholesome when it is free from pathogenic microorganisms and chemical substances that are hazardous to human health. This study aimed to investigate the microbial quality of water used for drinking, cooking, bathing and other purposes at universities in Nigeria.
Methodology and results: Water samples were collected from forty-four storage tanks across four selected universities. Total viable bacteria in the water samples were cultivated using the plate count agar. The isolation of total coliform and Escherichia coli were carried out on Harlequin™ E. coli/coliform agar (HA) medium, while media-faecal coliform was used for faecal coliform employing the membrane filtration technique. Physicochemical parameters such as alkalinity, pH, total alkalinity, total dissolved solid, total suspended solid, electrical conductivity, total hardness, fluoride and chloride ion concentrations, were evaluated in accordance with standard procedures. Data were compared statistically using MedCalc statistical software. Considering the heterotrophic bacterial counts, all water samples were unsatisfactory. For the total coliform counts, 50% of samples were satisfactory but suspicious, while remaining 50% were unsatisfactory. Faecal coliforms results showed that 50% of samples gave excellent quality, 25% showed satisfactory but suspicious quality, while 25% showed unsatisfactory result. There were no significant differences in the total viable, total coliform and E. coli counts of water sampled from universities A and D (p>0.05). The predominant bacterial species was Pseudomonas aeruginosa (23.17%), while the least encountered was Salmonella typhimurium (2.44%). All physicochemical parameters tested were within the acceptable limit.
Conclusion, significance and impact of study: This study revealed that the water used by students of studied universities was contaminated with potential bacterial pathogens. However, all physicochemical parameters tested were within the permissible standard limits and satisfied the requirements for domestic utility.
Aims: Bacterial lysate has been reported to possess many health-care-related benefits. This study aimed to determine the optimum conditions for producing Weissella confusa MBF8-1 lysate in two plant-based modified De Man, Rogosa, and Sharpe (MRS) media using the response surface methodology (RSM). In this study, we applied several condition factors and compared them to standard MRS media.
Methodology and results: W. confusa MBF8-1 was grown in two modified MRS media, which are MRS Vegitone and soy peptone modified-MRS. The optimized fermentation condition factors such as nitrogen sources (i.e., soy peptone, proteose peptone), dextrose concentrations, and fermentation time were measured, and the responses, such as bacteriocin-like inhibitory substance (BLIS) activity and lysate pH were observed. RSM results showed the diameter of BLIS activity-inhibition zone and pH decreases of the lysate produced in MRS Vegitone containing 1.50% dextrose, 0.75% proteose peptone for 11.75 h fermentation and in soy peptone modified-MRS containing 2.05% dextrose, 1.05% soy peptone for 7.53 h fermentation, i.e., 7.41 mm at 7.36, and 7.80 mm at 7.30, respectively. Whereas, lysate produced in standard MRS medium containing 2% dextrose, 1% peptone for 8 h fermentation showed 7.85 mm diameter of BLIS activity-inhibition zone at pH 7.26. W. confusa MBF8-1 lysate showed slightly lower pH, but higher BLIS activity when grown in standard MRS media compared to those of the two modified MRS media.
Conclusion, significance and impact of study: The data obtained provide the optimum condition of W. confusa MBF8-1 lysate production in plant-based media. The pH and BLIS activity possessed by W. confusa MBF8-1 lysate produced in soy peptone modified-MRS showed a more similar result as the standard one than the other modified one. Thus, the soy peptone modified-MRS is recommended as a plant-based alternative medium replacing standard MRS.
Aims: The objective of the present study is to evaluate the possibility of reversing the resistance of pathogens to antibiotics using phytochemicals from plant extracts as antibiotic-adjuvant.
Methodology and results: Twenty-one plants were collected from Podhigai Hills, Tamil Nadu, India and tested in this study. The susceptibility of burn wound isolates (Pseudomonas aeruginosa and Staphylococcus aureus) to antibiotics and the adjuvant activity of the aqueous plant extracts were tested using well diffusion assay. The impact of the plant extracts on quorum sensing was assessed using Chromobacterium violaceum as the model organism. The antibiofilm activity of the adjuvant and antibiotics was determined by crystal violet assay. The isolates which were resistant to more than one class of antibiotics (aminoglycoside, cephalosporin, fluoroquinolone and penicillin) were designated as multi-drug resistant bacteria. Combination of cefdinir-Citrullus colocynthis showed 17 mm inhibition zone which is greater than cefdinir (0 mm) against P. aeruginosa. The combination reduced quorum sensing with an inhibition zone of 30 mm. The same combination reduced 96% and 95% of the biofilm formed by P. aeruginosa and S. aureus, respectively at 16 h. Besides, cefdinir with Leucas aspera reduced quorum sensing with an inhibition zone of 28 mm. The combination reduced 94% and 95% of biofilm formed by P. aeruginosa and S. aureus, respectively at 16 h. The aqueous extract of C. colocynthis and L. aspera revealed the presence of flavonoids that possess adjuvant activity.
Conclusion, significance and impact of study: Cefdinir-C. colocynthis and cefdinir-L. aspera reversed the resistance of multi drug resistant bacteria to cefdinir. The flavonoids of C. colocynthis and L. aspera served as an adjuvant that potentiates the activity of cefdinir.
Aims: The oriental-based herbs Acalypha indica (AI), Centella asiatica (CA), and Sesbania grandiflora (SG) possess a broad range of undisclosed therapeutic activities which are edible and easily available throughout the year. To convert the herb extracts into a potential drug form, aqueous (A) and methanol (M) extracts of herbs were assessed alone and in combination for their antifungal-demelanising activity and nitric oxide (NO) immunomodulatory responses. A new bioactive synergistic and antagonistic assessments approach was made on these herbs to identify which extract combination qualifies as a natural drug candidate.
Methodology and results: Via micro-dilution technique, methanol extract of A. indica (AI-M) showed the strongest antifungal activity against Aspergillus niger, with a minimum inhibitory concentration (MIC) of 50 mg/mL and a minimum fungicidal concentration (MFC) of 100 mg/mL. Sublethal (50 mg/mL) and subinhibitory (25 mg/mL) doses of AI-M produced the optimal black pigmentation reduction to demelanise A. niger. The combinations AI-M+CA-M, AI-M+SG-M, and CA-M+SG-M showed similar antifungal activities (MIC = 100 mg/mL). At 500 µg/mL, CA-A and the combination CA-A+SG-A successfully induced RAW264.7 cells to produce NO at 17.85 µM and 40.84 µM, respectively. The combination of herbs extract showed synergistic interaction towards stimulation of NO production. In contrast, they demonstrated antagonism towards antifungal-demelanising properties. Compound identification of AI-M, SG-M, and SG-A were performed using a UHPLC-QTrap-MS/MS system, which detected phenolic compounds from various groups (cinnamic acids, benzoic acids, and flavonoids).
Conclusion, significance and impact of study: The combination of herb extracts showed better stimulation of NO production while the single herb extracts demonstrated good antifungal-demelanising activity. These findings help in the selection of herbs combination for potential natural drug discovery. A good combination of herbs demonstrated synergism to execute better bioactivities compared to individual herb extracts.
Aims: This present study focused on purification of fungal β-mannanase produced by Aspergillus niger USM F4 and also physicochemical characterisation of the purified enzyme.
Methodology and results: The purified β-mannanase with a molecular mass of ~47.4 kDa was demonstrated on SDS-PAGE gel. The enzyme signified a purification degree of 4-fold, with final specific activity of 196.42 U/mg. It reached an optimum catalytic activity at pH 4.0 and 60 °C. The thermal stability of the enzyme was up to 70 °C and maintained the 50% activity after 30 min at 80 °C. Meanwhile, the pH stability was in the range of pH 3.0 - 9.0 and a 30 min half-life at pH 10.0. All chemical substances manifested an inhibitory effect on purified β-mannanase, with SDS (28.16 ± 0.05% residual activity) as the strongest inhibitor, followed by cupric ion (Cu2+) (49.51 ± 0.09% residual activity). As a whole, the enzyme displayed a substrate specificity in the order of locust bean gum (LBG) > carboxymethylcellulose > soluble starch > xylan from oat spelt > α-cellulose. Its preference for LBG has generated the Km and Vmax values of 0.20 mg/mL and 9.82 U/mL, respectively.
Conclusion, significance and impact of study: The outcomes of our study offer potential for use at industrial scales, particularly in the oligosaccharides production that involve acid-related activity, wide-ranging temperature and pH stability.
Aims: Cruciferae crops failure such as cabbage generally due to heavy attacks by of Crocidolomia pavonana larvae. Metarhizium anisopliae is a species of fungus that can infect more than 200 insect pests including C. pavonana larvae. However, the direct application of M. anisopliae spore in the field is susceptible to UV rays from the sun, which can decrease the efficiency of M. anisopliae. Thus, this study aims to investigate the encapsulation performance of M. anisopliae spore with zeolite and magnesium silicate nanoparticles in terms of mortality and lethal time against 3rd instar C. pavonana larvae.
Methodology and results: Zeolite and magnesium silicate nanoparticles were chosen because they are non-toxic, environmentally friendly and able to maintain moisture, so that they are best used as protective materials for spores. The experiment was designed by Randomized Block Design (RBD) with a single factor. The obtained results showed that encapsulation of M. anisopliae spores with zeolite nanoparticles coating agent increased the mortality rate to 92.5% and accelerated the lethal time up to 1.075 days compared to only spore correspondingly 27.5% and 2.235 days. The M. anisopliae spores encapsulated with magnesium silicate nanoparticles also increased the mortality to 85.0% and accelerated the larval lethal time up to 1.150 days.
Conclusion, significance and impact of study: M. anisopliae spores that encapsulated with zeolite nanoparticles coating received higher mortality and faster lethal time to C. pavonana compared to those encapsulated with magnesium silicate nanoparticles. The encapsulation formulation of these two coatings can be used as bioinsecticide in controlling C. pavonana larvae.
Aims: The former Mamut Copper Mine, acid mine drainage site represents an anthropogenic altered landscape characterized by its acidic topsoil which is contaminated primarily with copper. Even though the mining operation was ceased at 1999, the bacterial diversity in this area has never been investigated. This study was conducted to ascertain the bacterial diversity of this abandoned copper mine and correlate it to the copper concentration in the soil.
Methodology and results: Soil samples were collected from 7 sites near the mine pit and the vicinity. Soil samples were assessed for soil copper elemental concentration using inductively coupled plasma optical emission spectrometry and bacteria were isolated via serial dilution followed by culture on nutrient agar plates. Phylogenetic analysis was done based on the full-length sequences of 16S rRNA gene. Twenty-four phylotypes were obtained from the 7 locations which originated from the phyla Firmicutes, Actinobacteria, Bacteroidetes and Proteobacteria. The results of the study indicated that site 2 (6.030223°; 116.658030°), located in between the mine pit and the mine factory with a copper concentration of 88.96 ppm, possessed the most diverse bacterial community with a Shannon diversity index (H) of 1.68, evenness (EH) of 0.94 and richness (S) of 6.
Conclusion, significance and impact of study: Current study revealed that there was a positive correlation between the copper concentration and the H index and the richness, but this was not reflected in the evenness. This is the first report of bacterial diversity from the former Mamut Copper Mine site. The data provided a valuable insight for the future monitoring of the bacterial community in this ecologically important niche.
Aim: DNA molecular size markers or DNA ladders play a vital role in molecular biology laboratories where DNA electrophoresis experiments are usually conducted. This study aimed to produce a 100 bp DNA ladder at laboratory scale, which could be applied to determine the size of DNA fragments in molecular biology experiments.
Methodology and results: In this study, 14 primers including 4 forwards and 10 reverses were designed based on the 16S rRNA gene sequence of Bacillus subtilis. These primers were able to amplify 10 DNA fragments with accurate sizes from 100 to 1000 bp. Furthermore, touchdown PCR was involved to maximize the specificity and yield of PCR products. Ten DNA fragments with the sizes including 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 bp were synthesized, and such bands were equivalent with commercial DNA ladders. Moreover, the quantity and quality of PCR products were measured using a nanodrop spectrophotometer. The optimal concentration ratios between such fragments (100-1000 bp) were 800, 300, 150, 150, 500, 50, 50, 50, 50 and 50 (ng/µL), respectively. These ratios showed the clear and high resolution on 1.5% agarose gel.
Conclusion, significance and impact of the study: The results indicated that 16S rRNA gene of B. subtilis was a potential material for DNA ladder preparation due to the multiple copies number of this gene. Furthermore, in combination with touchdown PCR, the nonspecific bands were reduced, and the products could be used directly without the need of purification step.
Aim: A novel endophyte, Streptomyces kebangsaanensis was isolated from the stem of a Malaysian ethnomedicinal plant, Portulaca oleracea in 2013. Studies on S. kebangsaanensis crude extract showed that it had antifungal activities and further work led to isolation of a novel compound, phenazine-1-carboxylic acid (PCA). This study investigated the combinatorial effect of PCA isolated from S. kebangsaanensis with amphotericin B on the growth of four clinical Fusarium solani isolates.
Methodology and results: Disk diffusion assay showed that the crude extract of S. kebangsaaneesis inhibited growth of all four F. solani isolates. Whereas, the compound PCA from this extract inhibited two of the tested F. solani isolates, UZ541/12, and UZ667/13 at minimum inhibitory concentration of 18.00 µg/mL Combinations of this compound with amphotericin B, reduced the minimum inhibitory concentration of amphotericin B for these two isolates from 8 to 0.13 µg/mL and 4 to 0.03 µg/mL respectively. Analysis of fractional inhibitory concentration index showed that a borderline synergism is present between the compound and amphotericin B.
Conclusion, significance and impact of the study: These results indicate PCA may be useful in improving actions of available drugs against antimicrobial resistant microorganisms.