Type IV Pili Can Mediate Bacterial Motility within Epithelial Cells
Vincent Nieto1, Abby R Kroken1, Melinda R Grosser1
1School of Optometry, University of California, Berkeley, California, USA.
Mbio
|August 22, 2019
Summary
Pseudomonas aeruginosa uses type IV pili (T4P)-dependent twitching motility to move within host cells. This novel intracellular bacterial motility does not rely on host actin or microtubules.
Area of Science:
- Microbiology
- Cell Biology
- Pathogenesis
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen known for its motility mechanisms.
- Type IV pili (T4P) mediate twitching motility, crucial for P. aeruginosa's virulence in host tissues.
- Previous studies linked T4P and twitching to P. aeruginosa's ability to infect and exit host cells.
Purpose of the Study:
- To investigate the role of twitching motility in the intracellular dissemination of Pseudomonas aeruginosa within host cells.
- To elucidate the mechanisms underlying bacterial movement and spread in the cytoplasm after host cell invasion.
Main Methods:
- Live wide-field fluorescent imaging and quantitative image analysis of infected host cells.
- Time-lapse microscopy to track bacterial movement and intracellular division.
- Transmission electron microscopy to examine bacterial localization and cellular compartments.
- Treatment with cytoskeleton-disrupting agents (latrunculin A, nocodazole) to assess host factor dependence.
Main Results:
- Wild-type P. aeruginosa exhibited active dissemination throughout the host cell cytosol at speeds exceeding 0.05 μm/s, independent of flagella.
- Mutants lacking T4P (pilA) or twitching motility (pilT) were impaired in dissemination, forming aggregates intracellularly.
- Bacterial intracellular motility and dissemination were not dependent on polymerized host actin or microtubules.
- Intracellular P. aeruginosa effectively disseminates using T4P-dependent twitching motility after escaping vacuolar compartments.
Conclusions:
- Pseudomonas aeruginosa employs a unique form of intracellular motility driven by T4P-dependent twitching.
- This motility mechanism is independent of host cell actin and microtubule cytoskeletons.
- T4P-mediated twitching is a critical factor for P. aeruginosa's intracellular spread and potential contribution to pathogenesis.
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