Researchers at the Helmholtz Centre for Infection Research (HZI) in Braunschweig have for the first time imaged the central transport channel for the protective bacterial capsule at the atomic level in three dimensions. With the help of cryo-electron microscopy, they succeeded in visualizing the Wza-Wzc protein complex, which transports the sugar molecules from the inside of the cell to the outside in gram-negative bacteria.

Many bacteria, including numerous pathogens, surround themselves with a capsule of sugar molecules. This protects against environmental influences such as dehydration and makes it more difficult for the human immune system to recognize it. The Wza-Wzc complex forms a continuous channel that spans the two membranes of gram-negative bacteria. The protein Wzc in the inner membrane acts as a ring-shaped octamer and makes contact with the equally octameric protein Wza in the outer membrane by means of a search movement. Together with the Wzy polymerase, this creates a transport system that polymerizes the sugar molecules and transports them to the outside.

The investigations were carried out on the non-pathogenic laboratory strain Escherichia coli K-12. The structural images show in detail how the channel is formed and which molecular components are involved in active transport. The study was carried out in cooperation with the Centre for Structural Systems Biology (CSSB) in Hamburg.

The researchers hope that the results will provide new starting points for active substances that could inhibit or prevent capsule formation. Without this protective shell, many resistant bacteria would be more easily attacked by the immune system. Against the background of increasing antibiotic resistance, this approach is gaining in importance.

The results have been published in the journal Nature Communications. (Original publication: Yuan et al., Nature Communications, 2026, DOI: 10.1038/s41467-026-69136-2)

Original paper:

Molecular insights into the capsular polysaccharide transporter Wza-Wzc complex | Nature Communications

Editor: X-Press Journalistenbüro GbR

Gender Notice. The personal designations used in this text always refer equally to female, male and diverse persons. Double/triple naming and gendered designations are used for better readability. ected.