Education/Science Project

Education/Science ProjectColiplate™ test kits are used extensively by educational organizations and students to study bacterial contamination in the environment and in surface waters used for recreational purposes, or as a drinking water source. These test kits are ideally suited to this purpose because of their ease of use, rapid results, accuracy and low cost.


PROJECT OR STUDY DESIGN

Most educational or student science projects focus on the sources or degree of bacterial contamination which exists in our environment. This is particularly important where surface waters of rivers, ponds or lakes are used for swimming or other recreational purposes, or are the source of drinking water. Sources of bacterial contamination can include agricultural activities, especially animal feedlots, dairy farms, hog farms, etc.; urban area stormwater runoff; sewage discharges or spills; areas of wildlife concentration such as geese, gulls, etc. The study design usually includes areas of suspected contamination and a control site of clean, uncontaminated water. The study could also examine how effective various water treatments are in killing or removing bacteria, such as boiling of contaminated water, chlorination (chlorine bleach), etc. In any of these types of studies, Coliplate™ testing will provide accurate, quantitative results of bacteria levels in the water sample.


INCUBATION OF Coliplate

Because most pathogens (disease-causing organisms) come from the intestines of warm-blooded animals, bacteria from this source are best incubated at body temperature (35 to 37°C or 95 to 99°F). Since Coliplate™s are incubating bacteria which may be in the water sample so that their presence can be identified, Coliplate™s must have a suitable incubation period before the bacterial counts can be made. At 35 to 37°C, the incubation period is 24 to 26 hours. However, at lower temperatures, the incubation period must be extended. The following guideline can be used:

Temperature (°C) Incubation Period (hours)
35 24
30 36
28 48
24 60
Best results are achieved with the warmer temperatures
and shorter incubation times.



Incubation options include the following:

  • Use of a laboratory incubator if available;
  • Purchase of a portable incubator from Bluewater Biosciences (see accessories);
  • Purchase of Styrofoam egg incubator at a local farm supply store;
  • Home-made incubator using a cardboard box or portable cooler with a 60-watt to 100-watt light bulb. This can be a small reading light or work light placed in the box. A thermometer should be used to regulate temperature and ensure that 40°C is not exceeded, since this can kill many bacteria; and
  • If no incubator is used, place the Coliplate in a warm location out of direct sunlight. The top of a refrigerator near the back is one of the best locations in a house because of the warm air rising up the back of the refrigerator from the heat exchanger. This will often provide temperatures in the 24 to 26°C range.


INTERPRETATION OF RESULTS

When adequate incubation time has been provided, Coliplate™ wells containing coliform bacteria (including E. Coli) will turn blue or blue-green. These can then be counted and converted to numbers of bacteria per 100 mL of water sample. If an ultraviolet light is available (black light), the number of wells containing E. Coli can also be counted, as these fluoresce under ultraviolet light. Bluewater Biosciences sells several types of UV lights for this purpose, including an inexpensive battery-operated model. Ultraviolet (black light) bulbs may also be available at a local hardware store.

More detailed information on how to use the Coliplate™ kit and interpret the results are provided in separate information sheets and can be found on the Coliplate™ product information page.

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