Why is potassium tellurite used in culture media?

Potassium tellurite is incorporated into culture media primarily for its ability to inhibit the growth of certain bacteria while selecting for others. This selective inhibition is particularly useful in microbiological studies where specific pathogens need to be isolated from a mixture of microorganisms. Specifically, potassium tellurite acts against various Gram-positive bacteria, allowing for the growth of Gram-negative organisms, which can be beneficial in the isolation of pathogens such as Corynebacterium diphtheriae. By selectively inhibiting non-target organisms, potassium tellurite helps in creating an environment that favors the growth of desired bacteria, facilitating accurate identification and study.