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Updated: Feb 8, 2026

Quantification of Interbacterial Competition using Single-Cell Fluorescence Imaging
Published on: September 2, 2021
The Agrobacterium Type VI Secretion System: A Contractile Nanomachine for Interbacterial Competition
Chih-Feng Wu1, Delaney A Smith1, Erh-Min Lai2
1Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, USA.
Abstract:
The bacterial type VI secretion system (T6SS) is a contractile nanomachine dedicated to delivering molecules out of bacterial cells. T6SS-encoding loci are in the genome sequences of many Gram-negative bacteria, and T6SS has been implicated in a plethora of roles. In the majority of cases, the T6SSs deliver effector proteins in a contact-dependent manner to antagonize other bacteria. Current models suggest that the effectors are deployed to influence social interactions in microbial communities. In this chapter, we describe the structure, function, and regulation of the T6SS and its effectors. We provide focus on the T6SS of Agrobacterium tumefaciens, the causative agent of crown gall disease, and relate the role of the T6SS to the ecology of A. tumefaciens.
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