External Stresses Affect Gonococcal Type 4 Pilus Dynamics

Area of Science:

• Microbiology
• Bacterial cell biology
• Molecular microbiology

Background:

• Bacterial type 4 pili (T4P) are essential extracellular structures involved in adhesion, motility, and gene transfer.
• T4P in *Neisseria gonorrhoeae* enhance survival against antibiotics and oxidative stress.
• The impact of diverse external stresses on T4P production and dynamics remains largely unexplored.

Purpose of the Study:

• To investigate the effects of various external stresses on T4P production and motor properties in *Neisseria gonorrhoeae*.
• To elucidate the mechanisms underlying stress-induced alterations in T4P dynamics.

Main Methods:

• Direct visualization of gonococcal T4P dynamics using advanced microscopy techniques.
• Quantitative analysis of T4P production and retraction rates under different stress conditions.
• RNA sequencing to identify molecular pathways affected by stress, including piliation machinery and energy metabolism.

Main Results:

• Under non-stress conditions, *N. gonorrhoeae* produces T4P at a high rate (~200 T4P/min) with immediate retraction following elongation.
• Antibiotics (azithromycin, ceftriaxone), cell wall/DNA synthesis inhibitors, hydrogen peroxide, and acidic pH significantly reduce T4P production.
• Hydrogen peroxide and acidic pH notably affect pilus length and motor function, despite T4P's protective role against some stresses.

Conclusions:

• Gonococcal T4P exhibit high dynamism, with production rates sensitive to environmental conditions.
• External stresses disrupt T4P biogenesis and function, potentially through downregulation of extrusion complexes and energy depletion.
• Understanding these stress responses is crucial for deciphering bacterial pathogenesis and developing effective therapeutic strategies.