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Figure 1: Nitrocellulose membrane. This membrane is used for the detection of total coliform and fecal coliformbacteria from samples of water. It has a 47 mm diameter and a pore size of 0.45 µm. The small pore size in the membrane filter will capture bacterial cells present in a sample of water during filtration. A grid is printed on the membrane to assist with counting colonies after incubation. (Brian Forster and Catalina Arango Pinedo, Saint Joseph’s University, Philadelphia, PA)

Figure 2: Filtration Column used in membrane-filtration. This filtration column can be used for the detection of total coliform and fecal coliform bacteria from samples of water. The column is first connected to a vacuum pump. A nitrocellulose membrane is placed between the chamber and catchment vessels. The water sample is then poured into the chamber of the column. (Brian Forster and Catalina Arango Pinedo, Saint Joseph's University, Philadelphia, PA)

Figure 3: Filtration Column used in membrane-filtration (Labeled view). (Brian Forster and Catalina Arango Pinedo, Saint Joseph’s University, Philadelphia, PA)

Figure 4: Vacuum set-up for membrane-filtration. This figure shows the filtration column with filter paper assembled and connected to a vacuum pump. When the vacuum is turned on, the water will filter through the nitrocellulose membrane into the catchment vessel.  Any bacteria present in the water will be trapped on the nitrocellulose membrane. (Brian Forster and Catalina Arango Pinedo, Saint Joseph’s University, Philadelphia, PA)

Figure 5: mENDO agar (A) and mFC agar (B) prior to incubation. These growth media are selective and differential media used in the detection of total coliforms and fecal coliforms, respectively. On mENDO agar, coliforms will form red colonies with a metallic sheen. On mFC media, fecal coliforms will form dark blue colonies. (Brian Forster and Catalina Arango Pinedo, Saint Joseph’s University, Philadelphia, PA)

Figure 6: mENDO agar (A) and mFC agar (B) prior to incubation (Labeled view). (Brian Forster and Catalina Arango Pinedo, Saint Joseph's University, Philadelphia, PA)

Figure 7: Placement of membrane onto agar following vacuum filtration. After filtering the water sample using the filtration column, the filter is aseptically transferred onto the plate, grid side up. The grid should be gently pressed onto the agar such that the nutrient agar can be absorbed into the membrane, allowing bacterial colonies to develop. (Brian Forster and Catalina Arango Pinedo, Saint Joseph’s University, Philadelphia, PA)

Figure 8: Detection of total coliforms following 24 hour incubation at 35 degrees Celsius Metallic green colonies indicate the presence of E. coli in a water sample. (Brian Forster and Catalina Arango Pinedo, Saint Joseph's University, Philadelphia, PA)

Figure 9: Detection of fecal coliforms following 24 hour incubation at 44.5 degrees Celsius Blue colonies are indicative of fecal coliform bacteria. (Brian Forster and Catalina Arango Pinedo, Saint Joseph's University, Philadelphia, PA)

Figure 10: Detection of fecal coliforms following 24 hour incubation at 44.5 degrees Celsius. This plate shows two different types of colonies. The blue colonies are indicative of fecal coliform bacteria. The yellow colonies are indicative of non-fecal coliform bacteria. When determining cell density of fecal coliform bacteria present in water samples, only blue colonies should be counted. (Brian Forster and Catalina Arango Pinedo, Saint Joseph’s University, Philadelphia, PA)

Figure 11: Detection of fecal coliforms following 24 hour incubation at 44.5 degrees Celsius (Labeled view). (Brian Forster and Catalina Arango Pinedo, Saint Joseph's University, Philadelphia, PA)