In a sample of 20 inpatients with a DSM-IV-TR/DSM 5 diagnosis of schizophrenia or schizoaffective disorder, investigators propose to conduct a prospective, 2 week observational trial to collect gastrointestinal stool samples in order to characterize the microbiota in people with schizophrenia and examine its variability over time. Participants may elect to participate for an additional two weeks, during which they will receive the prebiotic, oligofructose-enriched inulin (FOS), in order to examine its effects on the relative preponderance of butyrate-producing bacteria in the gut microbiome. Investigators will use an inpatient sample in order to standardize meals, exercise and environmental mediators. This is considered a feasibility, pilot study in order to apply for future grant funding. Investigators will recruit patients from the Treatment Research Program inpatient unit, Maryland Psychiatric Research Center, University of Maryland School of Medicine.