3M® Petrifilm™ E. coli/Coliform Count Plates
Publication No. 10162
The Petrifilm™ plate ready-made media system allows for easy counting of coliform colonies. An indicator dye in the plate colors all colonies red, and the top film traps gas produced by the coliform. In addition, the E. coli/Coliform Count Plate contains a dye that produces a blue precipitate around E. coli colonies. By counting all colonies, both red and blue, a total coliform count can be taken.
Store unopened E. coli/Coliform Count Plate foil pouches at or below 46 °F (8 °C). Use before expiration date on package. To seal an opened package, fold end over and tape shut. Keep resealed package at ≤25 °C (≤77 °F) and ≤50% relative humidity. Do not refrigerate opened packages. Use Petrifilm plates within one month after opening.
After use, Petrifilm™ E. coli/Coliform Count Plates will contain viable microbes. Do not open the plates unnecessarily. Use sterile techniques when handling them. Before disposal, plates should be soaked in a 10% bleach solution or autoclaved. They should then be disposed of in the normal garbage disposal channels. Set a good example for sterile technique for students when handling Petrifilm plates. Be sure to sterilize work areas before and after handling microbes and have students wash their hands before leaving the laboratory area.
Caution: This activity requires the use of hazardous components and/or has the potential for hazardous reactions. Be sure to review the Safety Precautions and Disposal sections and use sterile techniques when using these materials.
Correlation to Next Generation Science Standards (NGSS)†
Science & Engineering PracticesPlanning and carrying out investigations
Analyzing and interpreting data
Engaging in argument from evidence
Disciplinary Core IdeasMS-LS1.B: Growth and Development of Organisms
HS-LS1.B: Growth and Development of Organisms
Crosscutting ConceptsSystems and system models
MS-LS1-5. Construct a scientific explanation based on evidence for how environmental and genetic factors influence the growth of organisms.
It is easy to count coliform colonies on Petrifilm™ E. coli/Coliform Count Plates. An indicator dye in the plate colors all coliform colonies red, and the top film traps gas produced by the coliforms. Coliforms produce red colonies which have gas bubbles. Non-coliform colonies are red but do not have gas bubbles.
Petrifilm™ materials are a 3M® manufactured product and are to be used for non-commercial research and development purposes only.