Scientists have created a “living material” made from microbes that can respond to stimuli from their surrounding environment. It is hoped the material could find diverse applications in contaminant detection, highlighting damage, for example, to packaging, delivering nutrients or therapeutics and even in creating living photographs.
Biological systems are able to assemble and arrange tissues and structures, building in changes that reflect external stimuli, in ways beyond the capability of man-made materials. Consequently, the development of materials with these capabilities is highly desirable for monitoring purposes. Engineered living materials (ELMs) such as these have been created previously, however, the stringent growth conditions required for the microbes used have restricted their use to trained personnel. Scaling up production to facilitate their use as a technology has also consequently proved challenging. This latest research, published today in Nature Materials, however, overcomes these problems by taking its inspiration from the fermented drink kombucha.
Kombucha is a fermented culture of yeast and bacteria used to make a tea drink thought to have beneficial health properties. The kombucha mother culture from which the tea is made normally contains one or two strains of bacteria and at least two strains of yeast that live in symbiosis.
Scientists from Imperial College London and Massachusetts Institute of Technology combined genetically engineered baker’s yeast - the yeast typically found in kombucha is hard to engineer - with cellulose-producing bacteria to create a mutually beneficial symbiotic culture. The Komagataeibacter rhaeticus bacteria used was isolated from a kombucha mother culture and produces large quantities of cellulose that acts as a scaffold to support multi-functional enzymes produced by the yeast.
The researchers were able to engineer the yeast according to the needs of their system, for example to produce enzymes that fluoresced or that broke down target molecules. The systems for genetically engineering baker’s yeast are well established and fast, meaning that new strains with particular desired characteristics can be created quickly. The simple growth conditions required by the kombucha-style culture also mean that any new combination can quickly be established and bulked up ready for use. Both of these features make this a favorable ELM system.
In a press release, senior author Professor Tom Ellis from Imperial College London said, “The genetic toolbox for engineering these bacteria is underdeveloped compared to the number of tools available for manipulating yeast DNA. That is why we chose to use this division-of-labor strategy so we could first focus on engineering the yeast cells and explore the possibilities of various living functional materials."
The malleable nature of the yeast engineering system gives it utility in many areas opens doors to adapting the system to many purposes. In the study, the team incorporated yeast capable of sensing estradiol, a hormone found as an environmental pollutant, but this is just one example of the many possible applications. The team foresee that it could even be used to deliver essential nutrients or release therapeutics in response to stimuli.
“Although we are still far from a future in which people can cheaply grow their own biological sensors, our new system moves us forward by creating materials that are scalable and therefore more likely to be useful in the real world,” commented Dr Charlie Gilbert, one of the study’s authors.
Gilbert C et al. Living materials with programmable functionalities grown from engineered microbial co-cultures. Nat. Mater. (2021). https://doi.org/10.1038/s41563-020-00857-5