Type III Secretion Mechanisms in Pseudomonas aeruginosa Infections

Pseudomonas aeruginosa employs a specialised molecular syringe known as the Type III Secretion System (T3SS) to inject toxic effector proteins directly into host cells. Assembly of the injectisome spans the bacterial inner and outer membranes and culminates in a needle complex that punctures eukaryotic cell membranes. Activation of the T3SS is tightly regulated by environmental cues such as calcium limitation, host cell contact and quorum-sensing signals. The primary transcriptional regulator, ExsA, orchestrates a hierarchical cascade that controls expression of the secretion machinery and its cognate effectors, including ExoS, ExoT, ExoU and ExoY. Once inside the host cytosol, these effectors disrupt cytoskeletal dynamics, interfere with immune signalling pathways, induce apoptosis or necrosis and compromise barrier integrity. Through coordinated deployment of multiple effectors, P. aeruginosa achieves both evasion of phagocytic clearance and dissemination from local infection sites, contributing to its versatility as a respiratory and systemic pathogen.

Research from Nature Portfolio

Recent investigations have delineated the genome-wide regulatory network that governs T3SS deployment in P. aeruginosa. Using chromatin immunoprecipitation coupled with high-throughput sequencing, researchers identified ExsA binding sites across the genome and mapped its interactions with twenty other virulence-related transcription factors. This approach revealed unexpected crosstalk between T3SS regulation, quorum sensing circuits and nitrogen metabolism pathways, uncovering novel ExsA target genes and demonstrating how environmental stimuli are integrated to fine-tune effector expression. An online analytical platform derived from this work now allows dynamic modelling of T3SS regulatory responses under diverse growth conditions.

Type III Secretion Mechanisms in Pseudomonas aeruginosa Infections publication trend

The graph below shows the total number of articles in type iii secretion mechanisms in pseudomonas aeruginosa infections across all publications each year (not limited to Nature Index journals).

Technical terms

Type III Secretion System (T3SS): A multi-protein apparatus in Gram-negative bacteria that translocates effector proteins across the bacterial and host membranes.

Effector protein: A toxin delivered by the T3SS into host cells to modulate cellular processes and promote bacterial survival.

ExsA: The master transcriptional activator that initiates expression of T3SS structural genes and effectors in P. aeruginosa.

Phagosomal escape: The process by which intracellular pathogens rupture the phagosomal membrane to gain access to the host cell cytosol.

ADP-ribosyltransferase (ADPRT) activity: An enzymatic function of certain T3SS effectors that transfers ADP-ribose from NAD+ to host proteins, altering their function.

References

1. An integrated genomic regulatory network of virulence-related transcriptional factors in Pseudomonas aeruginosa. Nature Communications (2019).
2. Current concepts on Pseudomonas aeruginosa interaction with human airway epithelium. PLOS Pathogens (2023).
3. The Role of ExoS in Dissemination of Pseudomonas aeruginosa during Pneumonia. PLOS Pathogens (2015).
4. Killing from the inside: Intracellular role of T3SS in the fate of Pseudomonas aeruginosa within macrophages revealed by mgtC and oprF mutants. PLOS Pathogens (2019).