Curated collection of 16S rRNA amplicon sequencing studies comparing gut microbiome composition in Parkinson's disease patients vs. controls, including the landmark Sampson et al. 2016 Cell study (GEO: GSE71735), the Bedarf et al. 2017 eLife study, and the Scheperjans et al. 2015 Movement Disorders study. Provides the empirical basis for gut-brain axis hypotheses in PD pathogenesis.