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Outdoor Air Sampling Techniques
Published in Christopher S. Cox, Christopher M. Wathes, Bioaerosols Handbook, 2020
Media for isolation and enumeration of bacteria have ranged from non-selective nutrient, casitone and trypticase soy agars, often with the addition of 0.1–0.2%) cycloheximide to suppress fungi, to media selective for coliforms, such as Endo and eosin methylene blue agars.2,70,102,124,160,256 However, selective media in the Andersen sampler have sometimes recovered coliforms less well than nutrient agar, even when colonies on nutrient agar were replica plated onto clean plates of the same selective media.70 OED monolayers sometimes have been added to prevent desiccation of the medium70,102 but this can result in wet plates with the agar surface broken by the force of the sampling jets, and greater contamination than with untreated plates.70 Media have been supplemented in winter with 2.5% carboxyl methyl cellulose or 3% corn starch to prevent freezing. Bacteria have been detected 1.2 km downwind of the source, especially at night, with nearly half of the particles respirable (<5 μm).2,256
Biological hazards
Published in Sue Reed, Dino Pisaniello, Geza Benke, Principles of Occupational Health & Hygiene, 2020
Margaret Davidson, Ryan Kift, Sue Reed
Commonly used agars include non-selective nutrient or tryptic soy agar (TSA) for bacteria (Figure 16.4a) and malt extract agar (MEA) for fungi (Atlas, 2010); other selective agars, such as Endo, eosin methylene blue (EMB) and MacConkey agars, can be used. Differential media such as blood agar can be used to help presumptively identify bacteria through their growth morphology and ability to lyse red blood cells (Figure 16.4b). Some agars can be both differential and selective; examples include EMB agar on which E. coli develop a gold sheen (Figure 16.4c), and chromogenic agars, which are used to select for and presumptive identification of specific micro-organisms such as Salmonella colonies that form mauve colonies when cultured on chromagar (Figure16.4d). However, chromogenic agars are expensive compared with other types, as well as being prone to false positive results. Presumptive samples must be verified by more advanced identification methods.
Practical Considerations During Bioremediation
Published in Donald L. Wise, Debra J. Trantolo, Remediation of Hazardous Waste Contaminated Soils, 2018
Another interesting case was the isolation of a strain of bacteria from a crude oil spill in western Pennsylvania. This gram negative rod formed colonies that were tan in color and about 1 mm in diameter. The microorganism was characterized by cell membrane analyses of its fatty acids using gas chromatography.4 The results were confusing, because the fatty acid profile fit that of a Citrobacter species, a Shigella species, or a Salmonella species. Because this organism was isolated from crude oil contaminated soil at an industrial site and grew optimally at 20°C, it was expected of the three possibilities to be a Citrobacter. Further laboratory testing was done. Using eosin methylene blue (EMB), MacConkey, xylose lysine deoxycholate (XLD), hektoen, and tergitol 7 differential agars9 it was possible to eliminate Shigella and Salmonella as choices. The microorganism was identified as Citrobacter diversus. A second run of the sample gave essentially the same fatty acid profile and almost an identical similarity index for C. diversus. This indicates the need for basic bacteriological techniques to confirm an unknown microbe’s identification.
Evaluating the potability and human health risk of sachet water in Wukari, Nigeria
Published in Archives of Environmental & Occupational Health, 2023
Rachel Kusa, Williams Kwari Joshua
The temperature was measured in-situ using a mercury thermometer, pH using a calibrated pH meter, TDS using the gravimetric method by taking the water sample and evaporating it in an oven at 105 °C. TDS was then computed by taking the difference between the mass of the dried beaker and that of the beaker containing the residue and expressed in mg/L as described by APHA.23 In addition, color was determined using the Hazen method, nitrate using Hydrazine reduction and color intensity measurement with a spectrophotometer at an absorbance of 520nm, lead was determined by subjecting its filtrate to atomic absorption spectroscopy using a spectrophotometer, and iron using flame absorption Spectrophotometry.23Coliform count and E. coli were determined using Eosin Methylene Blue Agar.22
In-situ remediation of petroleum-contaminated soil by application of plant-based surfactants toward preventing environmental degradation
Published in International Journal of Phytoremediation, 2021
Emmanuel E. Okoro, Ikechukwu S. Okafor, Samuel E. Sanni, Tamunotonjo Obomanu, Taiwo S. Olugbenga, Paul Igbinedion
The Gram’s reaction and the colonies on the plate were three distinct bacteria which were: Pseudomonas aeruginosa, Micrococcus spp. and Escherichia coli (Table 3); these suggest that both extracts have similar phytochemicals and hence, denatured the enzymatic activities of Bacillus subtilis and Staphylococcus aureus which were no longer present in the treated soils. Eosin Methylene Blue Agar (EMB), was used to isolate coliform of fecal origin such as Escherichia coli (E.coli). The presence of E.coli in the soil sample is an index of fecal pollution. The polluted soil (sample P), yielded scanty growth of E. coli after 24 h of incubation at 37 °C and the colony appeared like a blue-purple metallic shin; Gram’s reaction and biochemical test identified the presence of E. coli (Table 4). The results also showed no significant growth on samples A and B after 48 h of incubation at 37 °C as indicated in Table 4. Sabouraud Dextrose Agar (SDA) supplemented with Streptomycin which is an antibiotic that helps to suppress the growth of bacteria, was used to isolate fungi present in the soil samples. The result shows that three fungi were isolated from the polluted soil (sample P) and they are: Mucor sp., Aspergillus niger and Rhizopus sp. (Table 5). It was also observed from Table 5, that Samples A and B showed no significant growth of the three fungi hence, a clear justification of their elimination from the soil samples A and B.