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Type VIIb secretion systems in Lactobacillales: insights from streptococci and enterococci
Caitlin S Wiafe-Kwakye1, Abigail E Glenn1, Brady L Spencer1
1Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, USA.
Journal of Bacteriology
|July 20, 2026
Summary
The type VII secretion system (T7SSb) is crucial for bacterial competition and virulence in Lactobacillales. This review covers its machinery, substrates, and roles in host interactions, highlighting future research directions.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- The type VII secretion system (T7SS) is an essential protein export machine in bacteria.
- T7SSb is well-characterized in some species but its role in Lactobacillales is recently understood.
- T7SSb mediates interbacterial competition, host colonization, and virulence.
Purpose of the Study:
- To review the current understanding of T7SSb in Lactobacillales.
- To discuss T7SSb machinery, substrates, and functions.
- To identify knowledge gaps and future research directions.
Main Methods:
- Literature review of experimental and observational studies on T7SSb in Lactobacillales.
- Analysis of published data on T7SSb core components and secreted effectors (LXG toxins, WXG100 proteins).
- Synthesis of information on T7SSb roles in bacterial antagonism, host-pathogen interactions, and ecological significance.
Main Results:
- T7SSb is experimentally validated in select Streptococcus and Enterococcus species.
- T7SSb contributes to cytotoxicity, virulence, and mucosal colonization.
- T7SSb plays a role in interbacterial antagonism and microbial community stability.
Conclusions:
- T7SSb is a significant virulence factor and modulator of bacterial communities in Lactobacillales.
- Further research is needed on effector delivery mechanisms, structural biology, host immunity interactions, and therapeutic targeting.
- Understanding T7SSb is critical for controlling bacterial pathogens and maintaining microbial ecosystems.
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