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Uncovering the secrets of the dynamic structure of the Bordetella injectosome, a key tool for infection

A new study published in the mBio journal brings fundamental insights into how Bordetella species, which cause whooping cough and other respiratory diseases in mammals, use their molecular “injector” to attack cells. A research team from IMIC CAS focused on the Bsp22 protein, which forms a unique needle-like structure at the end of this injectosom, also known as T3SS (Type III Secretion System).

12. 11. 2025

The study revealed that the Bsp22 protein forms flexible filaments that extend from the surface of the bacterium and can reach lengths of up to several micrometers. The key finding is the dynamics and growth pattern of these fibers. Scientists have shown that newly synthesized Bsp22 subunits are added to their ends, resulting in continuous elongation.

“Interestingly, the length and number of these filaments vary depending on the environment in which the bacteria are found,” explains Jana Kamanová, head of the Laboratory of Infection Biology. “We found that during infection of host cells, Bsp22 fibers are shorter and less numerous than when cultivated in a nutrient medium.”

The researchers also found that the reduction in filament size during infection is associated with a decrease in the bsp22 mRNA level. Nevertheless, the shortened fibers remain functional and capable of delivering proteins to infected cells.

This study provides important insights into how Bordetella cells adapt to different environmental conditions. Understanding the mechanisms of dynamic regulation of Bsp22 filaments could lead to developing new strategies for the prevention and treatment of diseases caused by these bacteria.

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Malcova I, Zmuda M, Valecka J, Kamanova J. Assembly and dynamic regulation of the tip filament of the Bordetella type III secretion system injectisome. mBio. 2025 Sep 22:e0113525. doi: 10.1128/mbio.01135-25.

Bacteria cells of the Bordetella species (Bb – Bordetella bronchiseptica, Bp – Bordetella pertussis) are shown in purple, while the protein Bsp22, which forms flexible fibers, is shown in green. Scale bar, 2 μm. (Malcova I, Zmuda M, Valecka J, Kamanova J. Assembly and dynamic regulation of the tip filament of the Bordetella type III secretion system injectisome. mBio. 2025 Sep 22:e0113525)

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