Probiotics. Conceptual coloured scanning electron micrograph (SEM) of probiotic flora in capsules. Probiotics are defined as live microorganisms that are believed to provide health benefits when consumed. Saccharomyces boulardii (yellow) is sometimes used as a probiotic with the purpose of introducing beneficial active yeast cultures into the large and small intestine, as well as conferring protection against pathogenic microorganisms in the host. Lactobacillus (pink/red) may be taken for general digestive and urogenital problems.