The laboratory grows standardized materials on a wide range of bacteria

Biologists at Rice University have turned bacteria into self-assembled building blocks. Engineered, living slime-like materials can be widely used to absorb environmental pollutants or as customized catalysts. Credit: Jeff Fitlow/Rice University

Engineered living materials promise to aid efforts in human health, energy and environmental remediation. Now it can be highly built and customized with less effort.

Biologists at Rice University have introduced centimeter-sized geometric slime-like colonies bacteria This is self-assembly from the bottom up. They can be programmed to absorb pollutants from the environment or to stimulate biological reactions, among the many possible applications.

Create autonomy Engineered Living Materials— or ELMs — has been a target of biologist Caroline Ajo Franklin long before she joined Rice in 2019.

“We’re making a substance out of bacteria that act like putty,” Ajo Franklin said. “One of the nice things about it is how easy it is to make, it just needs a little bit of movement, some nutrients and bacteria.”

A study was published this week in Nature Connections Details of in vitro creation of flexible and adaptable ELMs using Caulobacter crescentus as a biological building block. While the bacteria themselves can easily be genetically modified for different processes, designing them for self-assembly has been a long and complex process.

It involved engineering the bacteria to display and secrete the biopolymer matrix that gives the material its shape. C. crescentus actually produces a protein that covers its outer membrane like snake scales. The researchers modified bacteria to express a version of this protein, which they call BUD (bottom-up, as in from scratch), with properties that are not only favorable for the formation of ELMs (termed BUD-ELMs) but also provide markers for future recruitment. .

“We wanted to show that it’s possible to grow material from cells, like growing a tree from a seed,” said Sarah Molinari, a postdoctoral researcher in the Ajo-Franklin lab and the study’s lead author. “The transformative aspect of ELMs is that they contain living cells that allow the material to self-assemble and self-repair in the event of damage. Furthermore, they can be further engineered to perform non-native functions, such as the dynamic processing of external stimuli.”

The BUD-ELM is the most customizable example of an independently configured macroscopic ELM, said Molinari, who received Rice’s PhD in the laboratory of biologist Matthew Bennett. “It shows a unique combination of high performance and sustainability,” she said. “Thanks to its modular nature, it can serve as a platform for the generation of many different materials.”

ELMs grow in a beaker in about 24 hours, according to the researchers. First, a thin crust forms at the interface between air and water, which results in the seeding of the material. Constant shaking of the flask encourages ELM to grow. Once it expands to a sufficient size, the material sinks to the bottom and does not grow further.

“We found that the vibration process affects the volume of the material we get,” said co-author and graduate student Robert Tesorero, Jr. Currently she is the size of a fingernail.”

“Reaching to the centimeter scale with a cell less than a micron in size means that they collectively organize more than four orders of magnitude, about 10,000 times larger than a single cell,” Molinari added.

She said their functional materials are strong enough to survive in a jar on a shelf for three weeks at room temperature, meaning they can be transported without refrigeration.

The laboratory grows standardized materials on a wide range of bacteria

Living materials designed at Rice University can be customized for a variety of applications, including environmental remediation or as custom catalysts. Credit: Sarah Molinari/Aju Franklin Research Group

The lab demonstrated that BUD-ELM could successfully remove cadmium from solution and was able to perform biological catalysis, enzymatically reducing the electron carrier for glucose oxidation.

Because BUD-ELMs are marked for attachment, Ajo-Franklin said they should be relatively easy to modify for optical, electrical, mechanical, thermal, transport and catalytic applications.

“There’s a lot of room to play, and I think it’s the fun part,” said Tesoriero.

“The other big question is that while we love Caulobacter crescentus, it’s not the most popular baby on the scene,” said Ajo-Franklin. “Most people have never heard of it. So we’re really interested to see if these rules that we discovered in Caulobacter can be applied to other bacteria.”

She said that ELMs can be particularly useful for environmental treatment In low resource places. C. crescentus is ideal for this because it requires fewer nutrients to grow than many bacteria.

“One of my dreams is to use the material to remove heavy metals from the water, and then when it reaches the end of its life span, pull out a small portion and immediately transplant it into a new material,” Ajo-Franklin said. “That we can do this with the least amount of resources is a really compelling idea for me.”

The research co-authors are graduate student Switha Sridhar, postdoctoral researcher Rong Kai, lab director Jayashree Suman of Rice, Kathleen Ryan of the University of California, Berkeley, and Dong Li and Paul Ashby of Lawrence Berkeley National Laboratory, Berkeley, California. . Ajo-Franklin is Professor of Biosciences and CPRIT Research Fellow in Cancer Research.

Engineering Living Scaffolding For Building Material

more information:
Sarah Molinari et al., De novo Matrix of Living Macroscopic Materials from Bacteria, Nature Connections (2022). DOI: 10.1038 / s41467-022-33191-2

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