Bacteria isolation involves several techniques to separate different bacterial colonies from a mixed culture. This isolation is important because it helps in studying the particular organism with its distinctive traits. Bacteria have the habit of living in association with other organisms/bacteria, as this association will contribute to better survival of an organism. These microbial populations will cooperate together and obtain better nutrients for each other, because waste from one can serve as nutrients for the other. Likewise, the waste products of one's metabolism can provide favorable conditions for the growth of the other. These isolation techniques were developed by Robert Koch in 1883 in which he added agar to the liquid nutrient broth. With the addition of agar, the liquid medium was transformed into solid medium and helped isolate different bacterial colonies. In this medium, the nutrient broth supplements the nutritional needs of the bacteria while the agar provides the solid substrate for bacterial growth. The pure culture contains a similar type of bacteria from a single-parent colony with similar cells. There are many methods by which pure cultures can be obtained, a few are discussed below. SERIAL DILUTION. Serial dilution is a technique in which we find out the overall number of colonies present in the given sample. Serial dilution is followed by spread plate technique or cast plate technique for further isolation of microbes. SERIAL DILUTION PROCEDURE. This procedure is applicable to determine the total number of colonies from water and soil samples. The procedure includes the following steps. • A set of 6 test tubes is taken, which are then labeled as 1...... middle of paper ...... and will increase the number of selected colonies required. The new cells that will form as a result of the reproduction of old cells are called subcultures. This technique is of great importance as it is used to increase the number of cells as well as to increase the life expectancy of selected microbes. ENRICHMENT AND SELECTIVE ENVIRONMENTS. Bacteria can also be isolated by providing selective media to a bacterial culture. Since selective media can only support a specific group of microbes, their application helps isolate the required group from a non-required group. Specific materials are added to the culture plates that will prove to be a poison to an unrequired group, ultimately inhibiting the further growth of these microbes. When these microbes are eliminated, only the required group will grow and survive and can then be isolated..