Potassium tellurite is primarily used in microbiology as a selective agent in culture media to differentiate and identify certain bacterial species. It is particularly effective in isolating and identifying Corynebacterium species, including Corynebacterium diphtheriae, the causative agent of diphtheria. The compound inhibits the growth of most other bacteria, allowing for the selective growth of tellurite-resistant strains. Additionally, potassium tellurite is employed in biochemical research to study bacterial metabolism and resistance mechanisms. Its ability to act as an oxidizing agent also makes it useful in some analytical chemistry applications, particularly in the determination of specific compounds or elements in various samples.