CozE is a member of the MreCD complex that directs cell elongation in Streptococcus pneumoniae

Abstract

Most bacterial cells are surrounded by a peptidoglycan (PG) cell wall that is essential for their integrity. Major synthases of this exoskeleton are called penicillin-binding-proteins (PBPs) 1,2. Surprisingly little is known about how cells control these enzymes given their importance as drug targets. In the model gram-negative bacterium Escherichia coli, outer membrane lipoproteins are critical activators of the class A PBPs (aPBPs) 3,4, bifunctional synthases capable of polymerizing and crosslinking PG to build the exoskeletal matrix 1. Regulators of PBP activity in gram-positive bacteria have yet to be discovered but are likely to be distinct due to the absence of an outer membrane. To uncover gram-positive PBP regulatory factors, we used transposon-sequencing (Tn-Seq) 5 to screen for mutations affecting the growth of Streptococcus pneumoniae cells when the aPBP synthase PBP1a was inactivated. Our analysis revealed a set of genes that were essential for growth in wild-type cells yet dispensable when pbp1a was deleted. The proteins encoded by these genes included the conserved cell wall elongation factors MreC and MreD 2,6,7 as well as a membrane protein of unknown function (SPD_0768) that we have named CozE (coordinator of zonal elongation). Our results indicate that CozE is a novel member of the MreCD complex of S. pneumoniae that directs the activity of PBP1a to the midcell plane where it promotes zonal cell elongation and normal morphology. CozE homologues are widely distributed among bacteria, suggesting they represent a new family of morphogenic proteins controlling cell wall biogenesis by the PBPs.

CozEa and CozEb play overlapping and essential roles in controlling cell division in Staphylococcus aureus

“…The protein CozE (for coordinator of zonal elongation) was recently identified as an essential cell division protein in oval shaped pneumococcal cells, where it has been shown to be involved in regulation of proper cell elongation (Fenton et al, ; Straume et al, ). Spherical S. aureus does not elongate to the same extent as S. pneumoniae and other rod‐ or oval‐shaped bacteria, although a short elongation phase has been observed during the cell cycle (Pinho et al, ; Monteiro et al, ).…”

“…). CozE Spn has been shown to interact with MreC Spn , MreD Spn and DivIVA Spn (Fenton et al, ; Straume et al, ). We detected an interaction between CozEa and MreC, however, this was not the case for CozEb.…”

“…The results above demonstrate that CozEa and CozEb play functionally overlapping roles in controlling cell division in S. aureus , and both genes can be deleted individually. As mentioned above, a single protein CozE Spn (SPD_0768 in strain D39 and Spr0777 in strain R6), is shown to be essential for growth and proper cell morphology in S. pneumoniae (Fenton et al, ; Straume et al, ). To investigate whether the EzrA‐interactions detected here were specific for S. aureus or also relevant in S. pneumoniae , we used bacterial two‐hybrid assays to test the interaction between CozE Spn and EzrA Spn .…”

“…Most likely, the septal and peripheral cell wall growth in pneumococcal cells are mediated by separate protein machineries, whose actions are tuned by different regulatory proteins, such as StkP, MreCD, GpsB, DivIVA and EloR (Beilharz et al, ; Fleurie et al, ; Ducret and Grangeasse, ; Rued et al, ; Stamsås et al, ; Straume et al, ; Zheng et al, ). Another protein involved in regulation of cell wall synthesis in pneumococci, named CozE (for coordinator of zonal elongation, SPD_0768 in strain D39 and Spr0777 in strain R6), was recently identified (Fenton et al, ; Straume et al, ). CozE, a multi‐transmembrane spanning protein, was found to be essential for normal growth, however, its essentiality was abolished in the absence of the bifunctional penicillin‐binding protein PBP1a or the cell wall elongation proteins MreC and MreD (Fenton et al, ).…”

“…Another protein involved in regulation of cell wall synthesis in pneumococci, named CozE (for coordinator of zonal elongation, SPD_0768 in strain D39 and Spr0777 in strain R6), was recently identified (Fenton et al, ; Straume et al, ). CozE, a multi‐transmembrane spanning protein, was found to be essential for normal growth, however, its essentiality was abolished in the absence of the bifunctional penicillin‐binding protein PBP1a or the cell wall elongation proteins MreC and MreD (Fenton et al, ). In protein‐protein interaction assays, CozE was found to be associated with the same proteins (PBP1a, MreC, MreD) as well as DivIVA and PBP2b (Fenton et al, ; Straume et al, ).…”