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Review
. 2022 May 10:13:845563.
doi: 10.3389/fmicb.2022.845563. eCollection 2022.

Design Principles of the Rotary Type 9 Secretion System

Abhishek Trivedi  1   2   3 , Jitendrapuri Gosai  1   2   3 , Daisuke Nakane  4 , Abhishek Shrivastava  1   2   3
Affiliations
Review

Design Principles of the Rotary Type 9 Secretion System

Abhishek Trivedi et al. Front Microbiol. .

Abstract

The Fo ATP synthase, the bacterial flagellar motor, and the bacterial type 9 secretion system (T9SS) are the three known proton motive force driven biological rotary motors. In this review, we summarize the current information on the nuts and bolts of T9SS. Torque generation by T9SS, its role in gliding motility of bacteria, and the mechanism via which a T9SS-driven swarm shapes the microbiota are discussed. The knowledge gaps in our current understanding of the T9SS machinery are outlined.

Keywords: Flavobacteria; T9SS; bacterial motility; bacterial swarming; gliding motility.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
The diversity of bacterial protein secretion systems. Graphical representation of the currently known bacterial protein secretion systems ranging from Type 1 to Type 11 and their localization in the outer (OM) and cytoplasmic membrane (CM). Except T7SS (Gram positive), all the above shown secretion systems are found in Gram negative bacteria. Occurrence of T7SS mediated protein secretion is found within some Gram positive members of the phylum Actinobacteria that have an outer lipid layer.
FIGURE 2
FIGURE 2
Structure and function of the T9SS. (A) A cartoon of the nuts and bolts of the T9SS motor that drives protein secretion and gliding motility. T9SS substrates (SprB shown as an example) are transported to the periplasm via the Sec transport pathway. The CTD of T9SS substrates is cleaved during transport. A recent model suggests that the proton channel GldL powers the rotation of T9SS. (B) A cartoon of the molecular rack and pinion machinery that drives gliding motility. A model based on recent data suggests that the rotary T9SS pinion drives a cell-surface conveyor belt (rack). Cell-surface adhesins such as SprB are secreted by T9SS and are loaded onto the conveyor belt. Interaction of SprB with an external substratum results in screw-like gliding motility of the bacterial cell.
FIGURE 3
FIGURE 3
Collective motion of gliding F. johnsoniae. (A) Colony spreading pattern in a starved environment. (B) Left-turn biased cell movement at the edge of the colony. (C) Schematic of the vortex pattern formation and its possible roles.
See this image and copyright information in PMC

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