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Factors triggering type III secretion in Pseudomonas aeruginosa
Jaewha Kim1, Kyungseop Ahn1, Sungran Min1
1Department of Molecular Genetics and Microbiology, PO Box 100266, University of Florida, Gainesville, FL 32610, USA.
Microbiology (Reading, England)
|November 8, 2005
Summary
Pseudomonas aeruginosa type III secretion requires specific protein factors (TSFs) from serum and L broth, alongside low calcium. Albumin and casein were identified as key TSFs, suggesting a host-derived protein sensing mechanism for bacterial virulence.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- The type III secretion system (T3SS) in Pseudomonas aeruginosa is crucial for virulence and is regulated by environmental cues.
- While low calcium and host cell contact are known triggers, the precise signals initiating T3SS activity remain elusive.
Purpose of the Study:
- To identify the specific environmental signals that trigger the type III secretion system in Pseudomonas aeruginosa.
- To elucidate the role of host-derived proteins in regulating bacterial T3SS activity.
Main Methods:
- Investigated the requirement of protein factors from serum and L broth for T3SS effector secretion.
- Utilized calcium chelators like EGTA to assess the combined effect of low calcium and protein factors.
- Identified functional TSF molecules through biochemical analysis of serum and L broth components.
Main Results:
- Secretion of P. aeruginosa type III effector molecules necessitates protein factors, termed type III secretion factors (TSFs), in addition to low calcium.
- Albumin and casein were identified as the primary functional TSFs, both possessing low-affinity, high-capacity calcium-binding properties.
- TSF and EGTA together rapidly trigger secretion of pre-existing effectors, independent of active T3SS gene expression.
Conclusions:
- P. aeruginosa utilizes a sensing mechanism involving host-derived proteins (like albumin and casein) and low calcium to detect target cells for type III injection.
- Targeting this bacterial sensing mechanism, by disrupting low calcium or TSF detection, presents a potential strategy for controlling P. aeruginosa infections.