Isolation of Microorganisms from Soil Lab Report

In this lab report of isolation of microorganisms from soil ,we will learn how to isolate and count bacteria from soil to make a bacterial pure culture.

To plate soil sample of various dilution on culture media to count cfu/ml and isolate bacterial pure culture from soil for further studies

Soil contains enormous numbers and kinds of microorganisms in addition to bacteria there are also protozoa, fungi, molds, algae and microscopic worms in unbelievable numbers. The types of microorganisms will depend on the composition of the soil, moisture, PH and other related environment factors. Therefore no one such technique can be used for the isolation and enumeration of these varieties of microorganisms

There are different methods to isolate soil microorganisms but the viable plate count method is one of the most commonly used procedures for the isolation of most prevalent microorganisms.

This method is based upon the principle that the material containing microorganisms is cultured, each viable microorganisms will develop and grow into a colony. Hence the number of colonies appearing on the plates represents, the number of living organisms present in the sample.

In serial dilution agar plate method in known amount of material is suspended on agitated in a known volume of sterile water to make microbial suspension serial dilution are made by pipetting measured volume.

Finally 0.1 ml of adequate dilutions are added to the sterile petri plates in which 20 ml of cooled nutrient agar media is added. Plates are incubated in an inverted position for 24–48 hours at 37 °C. The number of colonies appearing on dilution plates are counted and the CFU are counted multiplied by the dilution factor to find out number of cells/gram


  • Soil sample

To read more — Isolation of Microorganisms from Soil Lab Report


From the result we conclude that in higher dilution more growth was observed than the lower dilution .Bacterial colonies in higher dilution was difficult to count. Separated colonies in lower dilution soil sample plated was studied and colony was counted to count cfu/ml, which is in calculation part of this practical.


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Originally published at on December 20, 2020.

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