Isolation of individual colonies

streak plate method

Nutrient preparations made in laboratory, used for the growth of the organism are called media singular: medium. Isolation of a specific bacterium from other bacterial species in a given sample allows microbiologists to study its structure and function, characteristics used in its identification.

Step 5: Incubate your plate based on the needs of the bacterial species you are trying to isolate.

Isolation of individual colonies

Beef extract is the commercially prepared dehydrated form of autolysed beef and is provided in the form of a paste. Nutrient agar typically contains 0. In the streaking procedure, a sterile loop or swab is used to obtain an uncontaminated microbial culture. On the initial region of the streak, many microorganisms are deposited resulting in confluent growth or the growth of culture over the entire surface of the streaked area. Peptone is dehydrated and supplied in the medium as powdered form. The importance of complex media is that they will support the growth of a wide range of micro organisms. During streak plate isolation, the inoculating loop is repeatedly sterilized in the flame of a Bunsen burner. Tools An inoculating loop is used to transfer microorganisms. If screw caped bottles are used, the cap must be loosened prior to sterilization process. Regardless of the type, deposit your sample on the outer edge of the agar plate and use your sterile loop to spread out the sample. Bacteria can only be isolated if they grow. Then, drag the loop through the second quadrant once, and zig-zag streak the third quadrant of your plate from the edge inward. Streak plate technique is used to grow bacteria on a growth media surface so that individual bacterial colonies are isolated and sampled. Isolated colonies indicate a clone of cells, being derived from a single precursor cell.

Then check for your colonies 24 hours later. During streak plate isolation, the inoculating loop is repeatedly sterilized in the flame of a Bunsen burner. The technique essentially dilutes the number of organisms and reduces their density.

t streak method

Step 2: Aseptically transfer a very small amount of your sample to the edge of your agar plate. Regardless of the type, deposit your sample on the outer edge of the agar plate and use your sterile loop to spread out the sample. Three physical forms are used: liquid or broth media; semisolid media; and solid media.

how to make a streak plate

The agar surface of the plate should be dry without any moisture such as condensation drops.

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How to Isolate Bacterial Colonies Using the Streak Plate Method