The multifarious roles of Tol-Pal in Gram-negative bacteria

ABSTRACT In the 1960s several groups reported the isolation and preliminary genetic mapping of Escherichia coli strains tolerant towards the action of colicins. These pioneering studies kick-started two new fields in bacteriology; one centred on how bacteriocins like colicins exploit the Tol (or mor...

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Bibliographic Details
Published in:FEMS microbiology reviews 2020-07, Vol.44 (4), p.490-506
Main Authors: Szczepaniak, Joanna, Press, Cara, Kleanthous, Colin
Format: Article
Language:English
Subjects:
Bacteria
Bacterial Proteins - genetics
Bacterial Proteins - metabolism
Bacteriocins
Bacteriology
Cell division
Cell Division - genetics
Cell Membrane - genetics
Cell Membrane - metabolism
Cell walls
Colicins
E coli
Escherichia coli
Gene mapping
Genetic aspects
Gram-negative bacteria
Gram-Negative Bacteria - metabolism
Membranes
Mutation
Peptidoglycans
Physiological aspects
Protonmotive force
Review
Roles
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Summary:ABSTRACT In the 1960s several groups reported the isolation and preliminary genetic mapping of Escherichia coli strains tolerant towards the action of colicins. These pioneering studies kick-started two new fields in bacteriology; one centred on how bacteriocins like colicins exploit the Tol (or more commonly Tol-Pal) system to kill bacteria, the other on the physiological role of this cell envelope-spanning assembly. The following half century has seen significant advances in the first of these fields whereas the second has remained elusive, until recently. Here, we review work that begins to shed light on Tol-Pal function in Gram-negative bacteria. What emerges from these studies is that Tol-Pal is an energised system with fundamental, interlinked roles in cell division – coordinating the re-structuring of peptidoglycan at division sites and stabilising the connection between the outer membrane and underlying cell wall. This latter role is achieved by Tol-Pal exploiting the proton motive force to catalyse the accumulation of the outer membrane peptidoglycan associated lipoprotein Pal at division sites while simultaneously mobilising Pal molecules from around the cell. These studies begin to explain the diverse phenotypic outcomes of tol-pal mutations, point to other cell envelope roles Tol-Pal may have and raise many new questions. The trans-envelope Tol-Pal assembly has at least two, recently defined, interconnected roles during cell division in bacteria; stabilising the outer membrane by actively depositing the peptidoglycan-binding lipoprotein Pal at division sites and orchestrating local structural changes in the peptidoglycan.
ISSN:0168-6445
1574-6976
DOI:10.1093/femsre/fuaa018