The gram-negative bacterial periplasm: Size matters.

Samuel I Miller,Nina R Salama

doi:10.1371/journal.pbio.2004935

Samuel I Miller, Nina R Salama

Open Access

https://doi.org/10.1371/journal.pbio.2004935

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Journal: PLoS Biology	Publication Date: Jan 17, 2018
Citations: 107	License type: CC BY 4.0

Affiliation: University of Washington, Fred Hutch Cancer Center

Abstract

Gram-negative bacteria are surrounded by two membrane bilayers separated by a space termed the periplasm. The periplasm is a multipurpose compartment separate from the cytoplasm whose distinct reducing environment allows more efficient and diverse mechanisms of protein oxidation, folding, and quality control. The periplasm also contains structural elements and important environmental sensing modules, and it allows complex nanomachines to span the cell envelope. Recent work indicates that the size or intermembrane distance of the periplasm is controlled by periplasmic lipoproteins that anchor the outer membrane to the periplasmic peptidoglycan polymer. This periplasm intermembrane distance is critical for sensing outer membrane damage and dictates length of the flagellar periplasmic rotor, which controls motility. These exciting results resolve longstanding debates about whether the periplasmic distance has a biological function and raise the possibility that the mechanisms for maintenance of periplasmic size could be exploited for antibiotic development.

Highlights

The outer membrane in some bacteria is anchored to the peptidoglycan polymer through abundant lipoproteins, which are inserted into the inner leaflet of the outer membrane through specific secretion systems [9]
The presence of specific areas in which the membranes are close together would explain how some of these ATP-binding cassette (ABC) transport and efflux pumps could work; these systems have periplasmic protein components that are essential for efflux, LPS, or other glycolipid transport but lack an intrinsic size or polymeric nature large enough to reach the outer membrane and provide a mechanism to promote transport
The periplasm contains many other components that necessitate at least some volume for the periplasmic space, most prominently the peptidoglycan polymeric layer surrounding the cell. It is unclear how these transporters get around this polymer and the width of the periplasm to contact the membrane, though recent work demonstrating that outer membrane lipoproteins can coordinate peptidoglycan synthesis through direct contact indicates that at least some proteins may fit through pores in peptidoglycan to accomplish important functions [14]

Summary

Introduction

The outer membrane in some bacteria is anchored to the peptidoglycan polymer through abundant lipoproteins, which are inserted into the inner leaflet of the outer membrane through specific secretion systems [9].

Results

Conclusion