The present disclosure provides for characterization of normal flora and identifying biomarkers in the gut of healthy, neurotypical subjects. Aspect of the disclosure provide for the characterization of the gut microbiome in ADS subjects, characterized by reduced richness and significant loss of the ‘Prevotella-like enterotype’ compared to neurotypical subjects. The relative abundance of genera Prevotella, Coprococcus, Prevotellaceae and Veillonellaceae are significantly lower in autistic children than in neurotypical children. Further, Prevotella, is one of the three main classifiers for the human enterotypes, along with Bacteriodes and Ruminococcus. These three core genera are among main contributors in the principle component analysis. ‘Prevotella-like enterotype’ was absent in the autistic group, while neurotypical samples showed an even distribution among the three enterotypes. The present disclosure provides for an understanding the association between gut microbiota, health, and disease states, and provides for potential diagnostic and therapeutic targets.