Type VI Secretion Systems in Bacterial Interactions

The Type VI Secretion System (T6SS) is a sophisticated molecular apparatus found predominantly in Gram-negative bacteria. Structurally analogous to the contractile tail of bacteriophages, the T6SS assembles a membrane-anchored baseplate and a contractile sheath-tube assembly that propels a puncturing spike through target cell envelopes. This machinery delivers a diverse arsenal of effector proteins directly into rival bacteria or eukaryotic hosts, mediating competition, niche colonisation and virulence. Across microbial communities, T6SS activity shapes population structure by eliminating competitors, modulating symbiotic relationships and influencing microbiome composition. At the cellular level, effectors can degrade cell walls, nucleic acids or membranes, while cognate immunity proteins safeguard the producer. The global significance of T6SS research spans human health, agriculture and biotechnology, with potential to inform novel antimicrobial strategies and biocontrol applications.

Research from Nature Portfolio

Recent work has elucidated a distinct membrane complex in Bacteroidota species that diverges from the canonical assembly found in Proteobacteria. Five novel components form a megadalton-sized scaffold anchoring the baseplate to the cell envelope. High-resolution electron microscopy and interaction mapping have defined the stoichiometry and organisation of this Bacteroidota-specific complex, revealing ancient co-option of unique structural motifs and functional convergence with non-homologous systems.

Investigations into iron acquisition have uncovered a specialised effector secreted by a Pseudomonas Type VI apparatus that co-opts outer membrane vesicles. The effector binds a bacterial signalling molecule and incorporates into vesicles, facilitating delivery of iron-laden cargo via established siderophore receptors. This study highlights unexpected interplay between cell–cell signalling, vesicle biology and T6SS-mediated nutrient uptake, extending the functional repertoire of secretion systems beyond direct antagonism.

Type VI Secretion Systems in Bacterial Interactions publication trend

The graph below shows the total number of articles in type vi secretion systems in bacterial interactions across all publications each year (not limited to Nature Index journals).

Technical terms

Type VI Secretion System (T6SS): A phage-tail-like nanomachine in Gram-negative bacteria that injects toxins into target cells.

Effector protein: A toxin or enzyme delivered by the T6SS that disrupts cellular processes in target organisms.

Baseplate: The cytoplasmic platform that organises tail-tube and sheath assembly before contraction.

Membrane complex: The multi-protein envelope anchor that secures the baseplate and sheath to the bacterial cell.

VgrG and PAAR: Spike-tip components that penetrate target membranes and can carry specialised effectors.

Hcp: Haemolysin-coregulated protein forming the inner tube through which effectors travel.

Contractile sheath: A protein structure that contracts to propel the inner tube and spike outwards.

References

1. Assembly of a unique membrane complex in type VI secretion systems of Bacteroidota. Nature Communications (2024).
2. A Pseudomonas T6SS effector recruits PQS-containing outer membrane vesicles for iron acquisition. Nature Communications (2017).
3. Burkholderia Type VI Secretion Systems Have Distinct Roles in Eukaryotic and Bacterial Cell Interactions. PLOS Pathogens (2010).
4. The Pseudomonas putida T6SS is a plant warden against phytopathogens. The ISME Journal: Multidisciplinary Journal of Microbial Ecology (2017).
5. VgrG and PAAR Proteins Define Distinct Versions of a Functional Type VI Secretion System. PLOS Pathogens (2016).