By Muhammad OsamaReviewed by Lexie CornerApr 3 2025A recent article in Nano Macro Small presents a new method for producing biohybrid materials by using bacteria to synthesize deoxyribonucleic acid (DNA) hydrogels outside the cell.
The goal of the research was to develop engineered living materials (ELMs) that combine the adaptability of biological systems with the durability of synthetic materials. This work has potential applications in sustainable biotechnology.
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Progress in Engineered Living Materials
Engineered living materials bring together ideas from synthetic biology and materials science. They aim to make use of the self-organizing abilities of biological systems to create materials that can adapt to their surroundings and regenerate themselves. This approach can reduce resource use and make material production more sustainable.
DNA hydrogels are promising candidates for ELMs. They are biocompatible, programmable, and respond to environmental changes. Typically, they are made using rolling circle amplification (RCA), a technique that creates long DNA strands that form into viscous hydrogel structures. However, their use within microbial systems, especially in bioelectrochemical systems (BES), has not been widely explored.
About this Research: Synthesizing Biohybrid Materials
In this study, the authors used Shewanella oneidensis, a bacterium known for its ability to transfer electrons to solid materials outside the cell. They aimed to engineer S. oneidensis to produce DNA hydrogels autonomously. This would help promote biofilm growth and increase current generation in BES.
To make this possible, the team used a protein-pairing system called SpyTag/SpyCatcher (ST/SC) to attach the DNA polymerase enzyme phi29-DNAP to the surface of the bacteria. This allowed the enzyme to carry out RCA on the cell surface. They also developed a version of the bacterium lacking certain nucleases (∆N SC) to prevent the breakdown of the extracellular DNA, which is important for hydrogel stability.
The researchers built plasmids to express surface anchor proteins, transformed S. oneidensis, and optimized culture conditions to allow bacterial growth and DNA hydrogel production at the same time. They tested a range of growth media and chemical environments to determine the best conditions. To assess hydrogel production and material properties, they used fluorescence microscopy and quantitative PCR (qPCR).
Key Findings: Performance of Engineered S. oneidensis
The engineered bacteria successfully produced DNA hydrogels in their environment. The ∆N SC strain showed improved stability and function compared to the wild-type. Attaching phi29-DNAP to the bacterial surface increased the production of large DNA molecules, confirming that the ST/SC system effectively supported enzyme activity on the cell surface.
Under optimal conditions, the ∆N SC strain generated around 8 micrometers of RCA product. Mechanical testing showed that the resulting hydrogels had two to three times higher viscosity than those made under less favorable conditions. This increase in viscosity is important for structural performance.
The researchers also found that producing DNA hydrogels directly in the environment supported biofilm development and improved current output in BES. The ∆N SC strain maintained current densities similar to the wild-type, which suggests it kept its ability to transfer electrons while also producing functional hydrogels.
These results show that engineered bacteria can act as living factories, creating materials that enhance microbial activity in biotechnological systems.
Applications of Engineered Living Materials
This research has significant implications across biotechnology, environmental remediation, bioelectronics, and biomedical engineering. Using S. oneidensis to produce DNA hydrogels may lead to more sustainable technologies that rely on bacteria to generate useful materials.
In BES, the hydrogels help stabilize biofilms and improve electron transfer. This could increase efficiency and output in systems that generate power from biological sources.
In biomedical applications, the programmable nature of DNA hydrogels supports controlled drug release and tissue scaffolding. Their ability to adapt to their surroundings also makes them suitable for use in pollution cleanup or resource recovery, where changing conditions are common.
Another potential use is in self-regenerating materials. Engineered bacteria could be used to repair or rebuild hydrogels over time. This could be valuable for smart materials, biosensors, and systems that need to operate in remote or unpredictable environments. Combining DNA hydrogels with conductive or redox-active components could also expand their use in advanced bioelectronic systems.
Conclusion and Future Work
This study introduced a new way to produce engineered living materials by using S. oneidensis to generate DNA hydrogels outside the cell. The results show that microbial systems can be used to create responsive, self-sustaining materials. These materials could be used in energy generation, environmental applications, and biotechnology.
Future research should aim to improve the performance of these biohybrid systems. This includes studying the mechanical properties of the hydrogels in more detail and examining how they affect bacterial metabolism. Adding features that respond to environmental cues and adapting these methods for use in more complex organisms could also expand their applications, especially in regenerative medicine and cellular engineering.
This work sets the stage for using engineered living materials in real-world applications. By using biological systems for material production, researchers can create efficient, adaptable, and sustainable solutions for a wide range of industries.
Journal Reference
Gaspers, P., et al. (2025). Extracellular Bacterial Production of DNA Hydrogels-Toward Engineered Living Materials. Nano Macro Small, 2502199. DOI: 10.1002/smll.202502199, https://onlinelibrary.wiley.com/doi/10.1002/smll.202502199
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