The Bicocca sampling days model: a participatory citizen science approach to environmental microbiome research and education.

Environmental microbiota are essential yet often overlooked, with urbanization driving microbial diversity loss and diseases of civilization. Public misconceptions, exacerbated by COVID-19, have widened the gap between microbiologists and society, highlighting the need for science-society integration. The Bicocca Sampling Days (BSDs) model offers a reproducible "citizen science" framework integrating research, education, and public engagement through large-scale microbiome sampling. Tested while assessing environmental microbiomes in different urbanized outdoors, 76 undergraduates participated in four sampling events, collecting 2429 samples in 8 h of effective sampling, achieving over than 303 samples/hour in 29 288.74 m2. Manual metadata curation revealed only 0.58% critical errors and no data loss, emphasizing the effectiveness of structured submission forms in ensuring data quality. Educational outcomes, assessed through a validated survey, significant gains in participants' perceived skills, understanding, and knowledge of microbiome sampling compared to non-participants. The BSDs model, including a step-by-step guide, illustrated protocol, and templates, is freely available for replication. Our findings demonstrate that citizen science can rival or complement traditional microbiome research in efficiency, scale, and data quality while broadening accessibility. BSDs offers a scalable tool to advance educational and societal, empower participation, and support informed decision-making.