Floating colonies: Engineering 3D microbial architectures in liquid cultures

Scientists have unveiled the world’s first platform for engineering three-dimensional (3D) microbial architectures directly within liquid cultures, marking a major breakthrough in microbiology. Developed by a research team led by Associate Professor Masayoshi Tanaka from the Department of Chemical Science and Engineering, Institute of Science Tokyo, Japan, in partnership with Suntory Global Innovation Center Ltd., the innovation allows for the creation and maintenance of complex microbial structures without relying on solid matrices such as hydrogels or agar. The system, named “floatony,” was detailed in a recent publication in Biofabrication. In nature, microbes such as those found in the gut, lungs, and biofilms do not exist as uniformly distributed populations. Instead, they form layered and clustered 3D arrangements that influence nutrient exchange, signal transmission, and oxygen availability. These spatial configurations play a critical role in shaping microbial behavior, interspecies interactions, and physiological responses. However, replicating such structures in the lab has been challenging due to limitations in conventional culture techniques. Traditional methods either mix microbes evenly in liquid or confine them to flat surfaces, failing to mimic the complexity of real-world environments. More sophisticated approaches have attempted to construct 3D microbial structures using hydrogels or other solid supports. While these methods can preserve the shape of microbial colonies, they often restrict cell movement, hinder molecular diffusion, and fail to replicate the dynamic, fluid conditions of natural microbial habitats. To overcome these constraints, Tanaka’s team devised a novel method involving a specialized “canvas solution” that allows microbial structures to remain suspended in liquid without settling or dispersing. The technique involves injecting a suspension of live bacteria, referred to as “bacterial ink”, into the canvas solution using a robotic arm. By precisely adjusting the physical properties of the canvas, the researchers ensured that the injected microbial structures remained stable while still retaining the inherent fluidity of the culture medium. Rheological studies helped establish optimal parameters for balancing structural integrity with the free movement of molecules and cells. As a test case, the team used Escherichia coli to demonstrate that bacteria embedded in floatonies remained viable and metabolically active. Enzymatic assays confirmed that the cells could process substrates and release reaction products into the surrounding liquid, indicating functional metabolic activity. According to Tanaka, this method offers a significant advantage over existing platforms because it preserves the natural dynamics of microbial communities, enabling more accurate modeling of their spatial organization. The potential applications of floatonies extend beyond basic research. They could provide valuable insights into how spatial arrangements affect microbial behavior, offering new tools for studying disease mechanisms, environmental processes, and industrial biotechnology. The ability to engineer microbial structures in liquid opens up possibilities for developing more effective probiotics, improving wastewater treatment, and advancing synthetic biology. With further refinement, the technology could enable scientists to explore microbial ecosystems under conditions that more closely mirror their natural settings. Researchers anticipate that floatonies will serve as a versatile platform for investigating the intricate relationships within microbial communities and for designing custom microbial systems tailored to specific biological or industrial functions.