Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

<span style="font-size:11.0pt;mso-bidi-font-size: 10.0pt;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-bidi-font-family:"Times New Roman";mso-ansi-language:EN-GB;mso-fareast-language: EN-US;mso-bidi-language:AR-SA" lang="EN-GB">Thermostable, alkaline and detergent-tolerant lipase from a newly isolated thermophilic <i>Bacillus</i> <i>stearothermophilus</i> </span>

179-188Lipases are the enzymes of choice for laundry detergent industries, owing to their triglyceride removing ability from the soiled fabric, which eventually reduces the usage of phosphate-based chemical cleansers in the detergent formulation. In this study, a novel thermo-alkaline lipase-producing strain identified as Bacillus stearothermophilus was isolated from the soil samples of olive oil mill. Enhanced lipase production was observed at 55°C, pH 11 and after 48 h of incubation. Among the substrates tested, xylose (a carbon source), peptone (a nitrogen source) and olive oil at a concentration of 1% were suitable substrates for enhancing lipase production. MgSO4 and Tween-80 were suitable substrates for maximizing lipase production. The enzyme was purified to homogeneity by a single CM-Sephadex column chromatography and revealed molecular mass of 67 kDa. The enzyme (BL1) was active over a wide range of pH from 9.0 to 13.0, with an optimum at pH 11.0, exhibited maximal activity at 55°C and retained more than 70% of its activity after incubation at 70°C or pH 13 for 0.5 h or 24 h, respectively. The enzyme hydrolyzed both short and long-chain triacylglycerols at comparable rates. BL1 was studied in a preliminary evaluation for use in detergent formulation solutions. This novel lipase showed extreme stability towards non-ionic and anionic surfactants after pre-incubation for 1 h at 40°C, and good stability towards oxidizing agents. Additionally, the enzyme showed excellent stability and compatibility with various commercial detergents, suggesting its potential as an additive in detergent formulations

Bacterial quality control of domestic and imported brands of bottled water in Saudi Arabia

Water is one of the most abundant and essential commodities of man occupying about 70% of the earth&apos;s surface and 60% of the human body therefore it should be continuously protected against microbial infections. Also, the mineral content in drinking water should be maintained within the acceptable range. Quality control of drinking water emerged with the invention of bottled drinking water. In this study, samples of bottled drinking water from Saudi markets were compared with tap water samples collected from different areas in Riyadh; both samples were tested for the presence of pathogenic bacteria. The bacterial isolates identified by the Biolog system (Hayward, CA, USA) include Bacillus cereus, Staphylococcus sp. and Pseudomonas aeruginosa in bottled drinking water, whereas tap water was mainly contaminated by P. aeruginosa. Bacterial contamination was highly observed in tap water samples and higher mineral content, determined by inductively coupled plasma-mass spectrometry (ICP-MS) was also observed in tap water. Bacterial cell count determined as CFU/ml was observed in bottled drinking water. Decreased water bacterial number was achieved with the solar disinfection system (SODIS) for one day with direct exposure to sunlight in polyethylene terephthalate (PET) plastic bottles. Thus water considered to be consumed by humans must maintain good microbial and mineral qualities within the acceptable ranges and must undergo effective treatment in order to reduce bacterial count and infection

New quinoxalinone inhibitors targeting secreted phospholipase A2 and α-glucosidase

Elevated blood glucose and increased activities of secreted phospholipase A2 (sPLA2) are strongly linked to coronary heart disease. In this report, our goal was to develop small heterocyclic compound that inhibit sPLA2. The title compounds were also tested against α-glucosidase and α-amylase. This array of enzymes was selected due to their implication in blood glucose regulation and diabetic cardiovascular complications. Therefore, two distinct series of quinoxalinone derivatives were synthesised; 3-[N′-(substituted-benzylidene)-hydrazino]-1H-quinoxalin-2-ones 3a–f and 1-(substituted-phenyl)-5H-[1,2,4]triazolo[4,3-a]quinoxalin-4-ones 4a–f. Four compounds showed promising enzyme inhibitory effect, compounds 3f and 4b–d potently inhibited the catalytic activities of all of the studied proinflammatory sPLA2. Compound 3e inhibited α-glucosidase (IC50 = 9.99 ± 0.18 µM); which is comparable to quercetin (IC50 = 9.93 ± 0.66 µM), a known inhibitor of this enzyme. Unfortunately, all compounds showed weak activity against α-amylase (IC50 > 200 µM). Structure-based molecular modelling tools were utilised to rationalise the SAR compared to co-crystal structures with sPLA2-GX as well as α-glucosidase. This report introduces novel compounds with dual activities on biochemically unrelated enzymes mutually involved in diabetes and its complications

Arabia

Postharvest fruit spoilage bacteria and fungi associated with date palm (Phoenix dactylifera L) from Saud

Biogenic green synthesis of MgO nanoparticles using Saussurea costus biomasses for a comprehensive detection of their antimicrobial, cytotoxicity against MCF-7 breast cancer cells and photocatalysis potentials.

Distinct morphological MgO nanoparticles (MgONPs) were synthesized using biomasses of Saussurea costus roots. The biomass of two varieties of Saussurea costus (Qustal hindi and Qustal bahri) were used in the green synthesis of MgONPs. The physical and chemical features of nanoparticles were confirmed by spectroscopic and microscopic techniques. The surface morphology of the obtained nanoparticles was detected at different magnifications by SEM and TEM microscopy and the size of nanoparticles were found to be 30 and 34 nm for Qustal hindi and Qustal bahri, respectively. The antimicrobial activity of the prepared MgONPs was screened against six pathogenic strains. The synthesized nanoparticles by Qustal bahri biomass exerted significant inhibition zones 15, 16, 18, 17, 14, and 10 mm against E. coli, P. aeruginosa, C. tropicalis and C. glabrata, S. aureus and B. subtilis as compared to those from Qustal hindi 12, 8 and 17 mm against B. subtilis, E. coli and C. tropicalis, respectively. MgONPs showed a potential cytotoxicity effect against MCF-7 breast cancer cell lines. Cellular investigations of MgONPs revealed that the prepared nanoparticles by Qustal bahri exhibited high cytotoxicity against MCF-7 cancer cell lines. IC50 values in MCF-7 cells were found to be 67.3% and 52.1% for MgONPs of Saussurea costus biomasses, respectively. Also, the photocatalytic activity of MgONPs of each Saussurea costus variety was comparatively studied. They exhibited an enhanced photocatalytic degradation of methylene blue after UV irradiation for 1 h as 92% and 59% for those prepared by Qustal bahri and Qustal hindi, respectively. Outcome of results revealed that the biosynthesized MgONPs showed promising biomedical potentials

Bariatric Surgery as Treatment Strategy of Obesity in Saudi People: Effects of Gut Microbiota

Obesity prevalence is rising globally, as are the number of chronic disorders connected with obesity, such as diabetes, non-alcoholic fatty liver disease, dyslipidemia, and hypertension. Bariatric surgery is also becoming more common, and it remains the most effective and long-term treatment for obesity. This study will assess the influence of Laparoscopic Sleeve Gastrectomy (LSG) on gut microbiota in people with obesity before and after surgery. The findings shed new light on the changes in gut microbiota in Saudi people with obesity following LSG. In conclusion, LSG may improve the metabolic profile, resulting in decreased fat mass and increased lean mass, as well as improving the microbial composition balance in the gastrointestinal tract, but this is still not equivalent to normal weight microbiology. A range of factors, including patient characteristics, geographic dispersion, type of operation, technique, and nutritional and caloric restriction, could explain differences in abundance between studies. This information could point to a novel and, most likely, tailored strategy in obesity therapy, which could eventually be incorporated into health evaluations and monitoring in preventive health care or clinical medicine

Isochlorogenic Acid Glucosides from the Arabian Medicinal Plant <i>Artemisia sieberi</i> and Their Antimicrobial Activities

A phytochemical investigation of the stems of the Arabian plant Artemisia sieberi afforded three new isochlorogenic acid derivatives, namely isochlorogenic acid A-3′-O-β-glucopyranoside (1), isochlorogenic acid A-3′-O-β-glucopyranoside methyl ester (2), and isochlorogenic acid C-3′-O-β-glucopyranoside (3), obtained along with thirteen known secondary metabolites belonging to distinct structural classes. The structures of the new metabolites were elucidated by modern spectroscopic techniues based on high-resolution mass spectrometry (HR-ESIMS) and 1D/2D nuclear magnetic resonance (NMR). All isolated compounds were tested for their potential antimicrobial activity against four different bacterial strains (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa), in addition to a fungal strain (Candida tropicalis), The results were expressed as the diameter of the clear zone (in millimetres) around each well. Compounds 1 and 3 (isochlorogenic acid A-3′-O-β-glucopyranoside and isochlorogenic acid C-3′-O-β-glucopyranoside, respectively) displayed remarkable antifungal effect and potent antibacterial activities against B. subtilis and S. aureus, respectively. 3α,4α-10β-trihydroxy-8α-acetyloxyguaian-12,6α-olide (6) and angelicoidenol 2-O-β-d-glucopyranoside (9) emerged as interesting dual antibacterial (selective on P. aeruginosa)/antifungal agents