Diversification of biofilm architecture among freshwater

Extracellular matrices that scaffold microbial biofilms offer a rich source of polymeric materials with a range of potential applications. However, our understanding of these matrices is largely restricted to model organisms that form biofilms with specific architectures. Examining biofilms from understudied niches has the potential to identify extracellular matrices with novel properties. Here, we targeted a resource-rich boundary at the top of the water column known as the air-liquid interface (ALI). ALIs lack a solid substrate for cellular attachment, suggesting that microbes utilize specialized biofilm architectures to persist at this boundary. We used samples from a lake to enrich for microbes that colonize the ALI. Mixed-species pellicle biofilms formed rapidly in these enrichments and displayed a pronounced ecological succession. We isolated 31 members of the genus IMPORTANCE: Microbial biofilms contain specialized polymers with immense industrial potential, yet only a subset of biofilm architectures has been studied in detail. Many aquatic microbes live within a boundary at the surface of lakes, rivers, and oceans known as the air-liquid interface (ALI). The strategies microbes use to form biofilms at this boundary remain poorly characterized. Our study investigated how bacteria from a freshwater lake accumulate at the ALI. Lake water samples incubated in nutrient medium formed a floating pellicle biofilm, and we isolated 31 bacteria from the genus