# A shared mechanism for Bacteroidota protein transport and gliding motility

## TL;DR

This paper reveals that Bacteroidota bacteria use a shared mechanism for movement and protein transport, involving a moving track inside the cell.

## Contribution

The study identifies a novel shared mechanism for gliding motility and protein transport in Bacteroidota.

## Key findings

- Outer membrane proteins are covalently attached to a moving internal track via disulfide bonds.
- A 3 MDa circular mini-track structure was determined using cryoEM from Porphyromonas gingivalis.
- The findings link gliding motility and T9SS-dependent protein transport mechanistically and evolutionarily.

## Abstract

Bacteria of the phylum Bacteroidota are major human commensals and pathogens in addition to being abundant members of the wider biosphere. Bacteroidota move by gliding and they export proteins using the Type 9 Secretion System (T9SS). Here we discover that gliding motility and the T9SS share an unprecedented mechanism of energisation in which outer membrane proteins are covalently attached by disulfide bonds to a moving internal track structure that propels them laterally through the membrane. We determined the structure of an exemplar Bacteroidota mobile track by obtaining the cryoEM structure of a 3 MDa circular mini-track from Porphyromonas gingivalis. Our discoveries identify a mechanistic and evolutionary link between gliding motility and T9SS-dependent protein transport.

Bacteria of the phylum Bacteroidota move by gliding and export proteins using a type-9 secretion system. Here, Liu et al. show that these two processes use a shared mechanism in which outer membrane proteins are covalently attached by disulfide bonds to a moving track structure inside the cell.