Bacteria in chain mail: Lactobacilli protect themselves with a lattice of proteins

Schematic overview of the cell wall composition of Lactobacillus: The S-layer (green and yellow) is the outermost layer that covers the entire bacterium like a chain mail. Image: Rehan – stock.adobe.com

We know them from the advertising for yoghurts or other probiotic foods: lactobacilli. They play an important role in the gut, but also in the microbiome of mucous membranes in other regions of our body. Researchers at the University of Graz have now succeeded for the first time in elucidating the three-dimensional structure of the protein layer on the surface of lactobacilli. It protects the bacteria like chain mail against external attacks. This knowledge is valuable. It opens up new possibilities for the treatment of intestinal diseases and for better drug delivery systems. The new findings were published in the scientific journal PNAS.

Lactobacilli are clearly among the good guys. They regulate the immune response, have an anti-inflammatory effect and displace pathogenic germs by docking onto human cells so that dangerous bacteria no longer find a place there. The surface layer, or S-layer for short, of the lactobacilli plays a key role in this interaction, for example with the intestinal wall. "As the outermost layer, lactobacilli form a lattice of proteins that surrounds them like chain mail," explain Theo Sagmeister and Nina Gubensäk, first authors of the latest publication and researchers in Tea Pavkov-Keller's working group at the Institute of Molecular Biosciences at the University of Graz. The team has now elucidated the detailed three-dimensional structure of the protein lattice for the first time.

"On the one hand, the S-layers of lactobacilli fulfil a protective function, on the other hand they interact intensively with human cells in the intestine. Both are very useful for drug delivery systems," says Tea Pavkov-Keller, emphasising the further significance of the new findings. "With the help of such structures, drugs could be transported safely and in a controlled manner to their destination in the body on a nanoscale, where they can then unfold their therapeutic effect in the right quantity," says the researcher.

Publication
The molecular architecture of Lactobacillus S-Layer: Assembly and attachment to teichoic acids
Sagmeister et al.
PNAS, 5 June 2024
https://doi.org/10.1073/pnas.2401686121

Nina Gubensäk, Christoph Grininger, Theo Sagmeister, Tea Pavkov-Keller, Lukas Petrowitsch and Christoph Buhlheller ©University of Graz/Tzivanopoulos

©University of Graz/Tzivanopoulos

The team of researchers: Nina Gubensäk, Christoph Grininger, Theo Sagmeister, Tea Pavkov-Keller, Lukas Petrowitsch and Christoph Buhlheller (f.l.t.r.). Photo: University of Graz/Tzivanopoulos

Gudrun Pichler

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