Considerations for the design of impactful citizen-science projects in microbiome research.

Citizen science offers a transformative approach to microbiome research. It allows the collection of rich, context-specific data from diverse sources, such as varying human populations and environments. Here, we describe guidelines that cover the design and implementation of community-engaged citizen-science projects focused on microbiome research. We outline essential research steps, beginning with defining the objectives and forming a transdisciplinary team, and continuing with community interaction, standardized self-sampling protocols, strategies for data processing, analysis and communication of results to community members and policymakers, as well as the implementation of robust data management practices that uphold participant privacy and data sovereignty. The guidelines highlight culturally-sensitive outreach strategies and capacity building in research teams and communities, emphasizing ethical considerations and tailored recruitment strategies. Community engagement may help reduce sampling bias but does not automatically ensure participant diversity: intentional inclusion strategies are essential. They cover culturally sensitive outreach, ethical considerations and tailored recruitment approaches that support inclusive participation and meaningful collaboration. These recommendations draw inspiration from a range of health and environment-related citizen-science projects in Belgium, Peru and Cameroon, and collaborative projects across the world. Specific examples highlight the importance of adapting methodologies to diverse cultural contexts and logistical constraints. While wet-laboratory sample processing and downstream analyses are detailed elsewhere, this Perspective focuses on the unique considerations and best practices needed for designing impactful cocreative citizen-science projects that combine scientific discovery with community, environmental health and well-being. It can serve as a blueprint for future citizen-science initiatives that aim to expand access to microbiome research, foster global collaboration and promote long-term research equity and environmental sustainability.