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 <i>Saccharomyces cerevisiae</i>. 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 (<i>n</i> = 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.