Visualization of the type III secretion mediated Salmonella-host cell interface using cryo-electron tomography

Area of Science:

• Microbiology
• Cell Biology
• Structural Biology

Background:

• Gram-negative bacterial pathogens utilize type III protein secretion systems (T3SSs) for host-pathogen interactions.
• T3SS activation leads to translocon pore insertion into host cell membranes for effector protein delivery.
• The initial bacterial-host cell contact and T3SS deployment are critical but poorly understood.

Purpose of the Study:

• To visualize the Salmonella T3SS-host cell interface at high resolution.
• To elucidate the mechanism of translocon deployment and effector translocation.

Main Methods:

• High-throughput cryo-electron tomography (cryo-ET) was employed.
• Visualization of the Salmonella-host cell interface.

Main Results:

• The intact translocon was resolved at unprecedented resolution.
• Translocon deployment in the host cell membrane was observed.
• An intimate bacterial-host cell association crucial for effector translocation was identified.

Conclusions:

• The findings provide critical data supporting the direct injection model of effector translocation.
• This study enhances understanding of T3SS function in bacterial pathogenesis.