Scientists at Lawrence Livermore National Laboratory have created a new way to 3D print living microbes in controlled patterns. This increases the possibility of using engineered bacteria to detect uranium and clean wastewater.
The research team created artificial biofilms that resemble the thin layers of real-world microbial communities using a new technique that uses light and bacteria-infused resin. Using LED light, the researchers suspended the bacteria in photosensitive resins and then “trapped” them in 3D structures. This was done with the Stereolithographic Apparatus to Microbial Bioprinting (3D printer) developed by LLNL. Projective stereolithography machines can print at a resolution of 18 microns, almost as thin as a human cell.
Researchers have demonstrated that the technology can create microbial communities with defined structures in their paper. The paper is available online in the Nano Letters journal. These 3D-printed biofilms were demonstrated to be applicable for rare-earth biomining and uranium biosensing applications. They also showed how geometry affects the performance of printed materials.
William “Rick,” LLNL bioengineer, stated, “We are trying to push the edge of 3D microbial culturing tech.” It is a neglected area, and its importance remains unexplored. Researchers are developing tools and techniques to help them better understand how microbes behave under highly controlled but complex conditions. We will be able to influence their interactions and enhance the performance of biomanufacturing processes by accessing and improving applied approaches that have greater control over the 3D structures of the microbial population.
Hynes explained that although it may seem simple, microbial behavior is complex and driven by the spatiotemporal characteristics of their environment. This includes the organization of members of microbial communities. Hynes explained that microbes’ organization could significantly impact their behavior, including how they grow, what food they eat, how cooperative they are with others, and how they protect themselves against competitors.
Hynes explained that previous methods of creating biofilms in the lab had given scientists little control over the microbial organization. This has limited our ability to understand complex interactions in natural bacterial communities. The ability to print microbes in 3D will enable LLNL scientists better understand how bacteria behave in natural environments and to investigate technologies like microbial electrosynthesis. This technology allows “electron-eating bacteria” (lactotrophs) to convert excess electricity during off-peak hours into biofuels, biochemicals, and other valuable products.
Hynes said microbial electrosynthesis is currently limited by inefficient interfacing between electrodes and bacteria. Engineers can create highly conductive biomaterials by 3D printing microbes into devices with conductive materials. This will allow for more efficient electrosynthesis.
The growing interest in biofilms is reflected in the industry’s use of them to remove ship barnacles, detect uranium deposits, and remediate hydrocarbons. Using synthetic biology capabilities at LLNL, where the bacterium Caulobacter crescentus has been genetically modified to extract rare-earth elements and detect uranium, LLNL researchers examined the impact of bioprinting geometry upon microbial function in their latest paper.
Researchers compared the recovery rates of rare-earth metals using different printed patterns. One set of experiments showed that cells printed in 3D grids could absorb metal ions faster than those made from bulk hydrogels. The team also published living uranium sensors. The researchers observed an increase in fluorescence when printing engineered bacteria compared to controls.
These biomaterials have important implications for many bio-applications. “The new bioprinting platform improves system performance and scalability and maintains cell viability. It also allows for long-term storage.”
Researchers at LLNL are still working on complex 3D lattices and new resins with better physical and printing performance. They are evaluating conductive materials like carbon nanotubes, hydrogels, and bio-printable electrographic bacteria to transport electrons. This will improve the efficiency of microbial electrosynthesis. They are also determining the best way to optimize bio-printed electrode geometry to maximize the mass transport of nutrients through the system.
Monica Moya, the LLNL bioengineer and coauthor of the technology, said that we are just beginning to understand how structure influences microbial behavior. The manipulation of microbes and the physiochemical environment to allow for more complex functions has many applications. These include biomanufacturing, remediation, and even developing engineered living materials that can be self-repairable or respond to their environment.
