Why is it important to sterilize the loop before and after each streak?

Sterilizing the loop before and after each streak is crucial to prevent cross-contamination between different microbial samples and to ensure accurate results. This practice eliminates any residual bacteria from previous samples, allowing for the isolation of pure colonies. Additionally, sterilizing the loop helps to maintain aseptic conditions, reducing the risk of introducing unwanted microorganisms into the culture. Overall, it ensures the integrity and reliability of microbiological experiments.