Karlsruhe Institute of Technology: Silicone sponge detects unknown bacteria
From our intestines to the bottom of the sea: microorganisms populate almost every habitat, no matter how hostile it is. The diversity of its survival strategies holds great potential for biotechnology. However, the majority of these organisms are unknown because they cannot be cultivated. In order to make this “microbial dark matter” more usable, a research team from the Karlsruhe Institute of Technology (KIT) has now developed a “sponge” made of porous, malleable silicone. Embedded in a chip, the material soaks up microorganisms from the environment, which are then available for further research. The results were published in ACS – Applied Material and Interfaces .
“It’s amazing that nobody has thought of using medical silicone for bacterial colonization,” says Christof Niemeyer, Professor of Chemical Biology at the Institute for Biological Interfaces-1 of KIT. The advantages are obvious: The special polymer, which is also used for breast implants, for example, does not interact with its environment, but is easily modifiable, durable and inexpensive. He and his team only came up with it indirectly, but the results exceeded their expectations, according to the chemist. “The material is able to absorb microorganisms from the environment, no matter how wet or dry it is. The prerequisite for this: the silicone had to be processed into a porous, spongy structure,” he explains.
Especially many different bacteria “caught”
In the course of several experiments it became apparent that the silicone sponge captures a particularly wide range of microorganisms in its numerous holes. For example, the team was able to identify members of the Actinobacteriota in the dry air of a chicken farm . The exciting thing about it: It is precisely these microorganisms that are needed in the production of antibiotics. They can also produce substances that could help with certain types of cancer, for example. “If we capture new bacteria with the sponge, they can be used for new impulses in biomedicine, for example,” estimates Niemeyer.
A similar thing happened after immersing the silicone sponge in a pike-perch breeding tank. Compared to a conventional material that is already on the market, the researchers found, among other things, a large number of bacteria that belong to the candidate phyla radiation , which has not yet been researched much . “These microorganisms make up about 70 percent of the microbial dark matter because they have not been able to be cultivated so far,” explains Professor Anne-Kristin Kaster, who and her team at the Institute for Biological Interfaces-5 of KIT analyzed the captured microorganisms using the latest sequencing technology.
Silicone sponge made with table salt
The team also demonstrated that the sponge can enrich selected bacteria when properly prepared. For example, microorganisms that process glyphosate have been “baited” into the sponge with this pesticide. Even when in contact with soil samples, the porous material was colonized by microbes within a few days.
In order to make the medical silicone habitable for microorganisms, the researchers had to reprocess the material. The team mixed table salt into the polymer, which was then redissolved. This resulted in small holes connected by fine passages: the desired spongy structure. In order to be able to use these for the applications, the researchers then formed a “chip”. This small unit is made of the same silicone as the sponge, but in its homogeneous, non-porous form.
“What is practical here is that the silicon chip – as a combination of sponge and chip – can be produced very easily using standard methods, in almost any size and quantity,” says Niemeyer. “You end up with a robust research tool that can be used in virtually any environment. Everything indicates that this chip is very well suited for the systematic investigation of microbial dark matter and also opens up interesting possibilities for the cultivation of previously uncultivable microorganisms.”