Final answer:
To properly open a Petri plate for streaking agar, one should lift the lid just enough to insert the sterilized inoculating loop. This method is vital to reduce contamination risk and to ensure that individual colonies can be isolated for pure cultures.
Step-by-step explanation:
The correct way to open a Petri plate to streak the agar is by lifting the lid only enough to get the loop inside. This is crucial to maintain the sterility of the culture and to prevent contamination. The process involves using a sterilized inoculating loop to pick up a colony and then transfer it to the agar surface. The bacteria is then spread over the plate in a systematic manner to achieve a streak plate which allows for isolation and growth of individual colonies that can be used to create pure cultures.
It is important to follow strict techniques while handling cultures on agar plates as they do not survive long due to dehydration and contamination risks. Therefore, it's essential to minimize the exposure of the agar surface to the environment. After streaking, the plate should be incubated at room temperature for a period, typically up to a week, to allow colony formation that can be observed and studied further.