Abstract: The present disclosure provides embodiments of a method for characterizing microbial populations. Exemplified by methods for characterizing microbiota in vaginal samples, the methods provided herein are widely applicable to the characterization of microbial communities. Also provided are probiotic regimens and methods for selecting appropriate probiotic regimens based on the normal vaginal microbiota of a subject. Reagents and kits for detecting normal vaginal microbiota and diagnosing pathogenic microorganisms in the vagina are also provided.