It's Alive! Materials Derived from Kombucha

If you've ever brewed kombucha at home, you might notice a gelatinous layer forming atop the tea. This layer is a cellulose pellicle produced by acetic acid bacteria during fermentation. The yeast present contributes to the effervescence of the kombucha, generating carbon dioxide and ethanol, which together create its unique taste. However, these organisms hold potential beyond just making a refreshing drink.

A recent study published in Nature Materials highlights a collaboration between the Tom Ellis and Tim Lu teams from Imperial College and MIT. They engineered "living materials" inspired by kombucha, utilizing two genetically modifiable organisms: a laboratory strain of budding yeast (Saccharomyces cerevisiae) and a cellulose-producing bacterial strain, Komagataeibacter rhaeticus, sourced from kombucha.

The bacteria can form a robust cellulose pellicle in just a few days at ambient temperature. The researchers cleverly devised methods to suspend the yeast within these cellulose layers, allowing them to modify the yeast to detect environmental pollutants or light and respond with signals. This innovative approach led to the creation of a synthetic cell community that collaborates to produce programmable living materials.

Unleashing the Potential of Fungi

Fungi are rich sources of bioactive compounds. For instance, cephalosporin and penicillin, the first discovered antibiotic, both originate from fungi. However, many fungi are challenging to cultivate in lab settings since their genes are often only activated in their natural habitats. A fungus found in the Amazon rainforest might produce a valuable new treatment, but once taken to the lab, it may cease production.

To tackle this issue, a study in Scientific Reports introduces a CRISPR-based gene activation tool specifically designed for fungi. This technology employs a "deactivated" version of Cas9 that can recognize but not cut DNA, combined with an activator protein known as VPR. Researchers successfully inserted this dCas9-VPR fusion protein into fungal cells using a method suitable for various filamentous fungal species.

As a proof of concept, the team activated genes responsible for producing a compound called macrophorin in the fungus Penicillium rubens, the same species that led to the discovery of penicillin by Alexander Fleming.

A Marvel of Protein-Making Machines

Ribosomes are intricate molecular machines made up of numerous proteins, capable of reading approximately 60 mRNA "letters" each second and rapidly assembling amino acids into proteins. Although most ribosomes work with a limited set of 20 amino acids, bioengineers have been gradually expanding this "alphabet."

In a study featured in ACS Synthetic Biology, researchers created ribosomes outside of cells (in vitro) that can produce proteins with non-canonical amino acids at any position. Achieving this required recoding the E. coli genome, eliminating a gene called release factor 1, and extracting the cellular contents. Ultimately, they succeeded in constructing a GFP protein containing two different non-canonical amino acids simultaneously: p-acetyl-phenylalanine (pAcF) and p-azido-phenylalanine. This advancement represents a significant step forward in cell-free protein manufacturing.

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