Taking microbial art beyond the laboratory: safe, simple, and scalable public engagement at the Osaka Expo

Public perceptions of microbes remain predominantly negative, often emphasizing contamination and disease rather than their roles in food, ecosystems, and health. Hands-on microbial art has emerged as a promising way to make microbial life visible and approachable, but most implementations occur in classrooms or small workshops where access to laboratory infrastructure and biosafety oversight are available. As a result, their reach is limited. Here, we describe a practical framework for implementing microbial art in an open public venue based on an outreach activity at the Osaka Expo in which approximately 500 visitors created "microbial paintings" using Saccharomyces cerevisiae. To enable safe, bench-free deployment at scale, we prepared YPD agar plates in advance, vacuum sealed them for room-temperature storage and transport and activated them on site by adding a suspension of dried commercial baker's yeast. This design eliminated refrigeration requirements, minimized biosafety risks by using a familiar GRAS organism, and kept contamination and spills manageable under crowded conditions. After the event, plates were incubated, photographed, and shared through a password-like online gallery, where participants could also complete an anonymous questionnaire. We analyzed paired before/after attitude items together with free-text comments using a BERT-based sentiment classifier. Among respondents who provided comments (n = 27), we observed small but measurable positive shifts in impressions of microbes, particularly among those who had initially reported a neutral view. While our data primarily capture affective change, this case study illustrates that large-scale, hands-on microbial art can be conducted safely outside the laboratory and may serve as a useful model for educators seeking to engage broader publics with microbiology.