Final answer:
After streaking out the initial inoculum, the inoculating loop must be sterilized by flaming until red hot and then cooled before use. This prevents contamination and is repeated between each step of the streaking process to aid in obtaining isolated colonies for pure culture preparation.
Step-by-step explanation:
After streaking out the initial inoculum with an inoculating loop, it is essential to sterilize the loop to prevent contamination of the cultures. The process involves heating the loop in a flame until it is red hot and then allowing it to cool before using it again. This is done between each step of the streak plate method. After initially spreading bacteria on an agar plate (Step 1), the loop should be flamed. Subsequently, cool the loop in the agar and then overlap the initial streak 3-4 times (Step 2), before continuing to spread the bacteria across the plate. This flaming and cooling process between steps ensures that the number of bacteria is reduced with each streak, aiding in the development of isolated colonies after incubation.
Once the entire surface of the agar plate is covered, the streak plate subcultures should be placed in an incubator at the specified temperature and time. After incubation, isolated colonies may be visible, from which a pure culture can be prepared if needed. The cooled, sterilized loop is also used to transfer individual colonies for further study, ensuring that the study of microorganisms is conducted with uncontaminated cultures.