Determination of Microbial Population in Water by Filter Disc Method

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BACKGROUND

Water contains a large number of bacteria. There are lots of methods by which we can estimate the number of bacteria present in water. Filter disc method is one of the important methods for determining the microbial population with much accuracy.1

So, the objective of this test is to determine the microbial population in water by filter disc method.

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REQUIREMENTS

Sample:     Water sample

Media:     Differential media (endo or eosin- methylene blue agar

Others:     Membrane filter (0.45 micro-metre pore size)

Graduated cylinder

Sterile filtering unit

Metal forceps

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PROCEDURE

First take 100 ml of water sample and filter it through 150 µm thick and 0.45 µm pore size membrane filter using a sterile filtering unit.2,3 Then after filtration, remove the filter from the filtration unit very carefully with the help of a metal forcep and then place it onto the surface of the differential media. After placing close the plates and incubate it at 37oC for about 24 hours. When incubation is done bring out the plates and count the total number of colonies. Then estimate the total amount of water that has been used and accordingly we can estimate the number of colonies formed per volume of water.2-5

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CONCLUSION

It is a very effective method for calculating the number of microbes present in a sample of water by utilizing a filter disc for removing the microbes from the solution.

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REFERENCES

  1. Gaspar AJ, Leise JM. Inhibitory effect of grid imprints on growth of Pasteurella tularensis on membrane filters. J Bacteriol. 1956;71(6):728–731.
  2. Geldreich EE, Kabler PW, Jeter HL, Clark HF. A delayed incubation membrane filter test for coliform bacteria in water. Am J Public Health Nations Health. 1955;45(11):1462–1474.
  3. Mccarthy JA. Comparative coliform densities in water by membrane filter test and by multiple tube technic. Am J Public Health Nations Health. 1955;45(12):1569–1577.
  4. Morgante O, Murray EG. The isolation of mycobacterium tuberculosis by filtration technique from cerebrospinal fluid. Can J Microbiol. 1955;1(5):331–338.
  5. Rogers DE, Cooke GM, Meyers CE. The detection of tubercle bacilli in mouth wash specimens by the use of membrane filter cultures. Am Rev Tuberc. 1955;71 (3 pt 1):371–381.