Abstract
Until now, peptidoglycan O-acetyl transferases (Oat) were only described for their peptidoglycan O-acetylating activity and for their implication in the control of peptidoglycan hydrolases. In this study, we show that a Lactobacillus plantarum mutant lacking OatA is unable to uncouple cell elongation and septation. Wild-type cells showed an elongation arrest during septation while oatA mutant cells continued to elongate at a constant rate without any observable pause during the cell division process. Remarkably, this defect does not result from a default in peptidoglycan O-acetylation, since it can be rescued by wild-type OatA as well as by a catalytic mutant or a truncated variant containing only the transmembrane domain of the protein. Consistent with a potential involvement in division, OatA preferentially localizes at mid-cell before membrane invagination and remains at this position until the end of septation. Overexpression of oatA or its inactive variants induces septation-specific aberrations, including asymmetrical and dual septum formation. Overproduction of the division inhibitors, MinC or MinD, leads to cell filamentation in the wild type while curved and branched cells are observed in the oatA mutant, suggesting that the Min system acts differently on the division process in the absence of OatA. Altogether, the results suggest that OatA plays a key role in the spatio-temporal control of septation, irrespective of its catalytic activity.
Highlights
Peptidoglycan (PG), the major cell-wall compound in Grampositive bacteria, is composed of a polymer of the disaccharide Nacetylmuramic acid (MurNAc)-(b-1,4)-N-acetylglucosamine (GlcNAc) associated with peptidic stems linked to MurNAc [1]
The L. plantarum oatA Mutant is Affected in the Control of Cell Length and Cell Cycle In order to evaluate the contribution of MurNAc O
Overexpression of oatA Leads to Curved Cells and Aberrant Septation As OatA is localized at a septal position during all steps of the division process and as its depletion affects the uncoupling of the elongation-septation process, we investigated the impact of its overproduction on cell morphology
Summary
Peptidoglycan (PG), the major cell-wall compound in Grampositive bacteria, is composed of a polymer of the disaccharide Nacetylmuramic acid (MurNAc)-(b-1,4)-N-acetylglucosamine (GlcNAc) associated with peptidic stems linked to MurNAc [1]. In L. plantarum, the addition of an O-linked acetyl group on both MurNAc and GlcNAc, as well as the presence of a covalentlylinked glycopolymer on MurNAc called wall teichoic acid (WTA), have been reported [2,3]. In Gram-positive bacteria, MurNAc O-acetylation is catalyzed by the membrane-bound OatA protein, an O-acetyltransferase composed of 11 transmembrane segments at the N-terminus and a surface-exposed O-acetyltransferase catalytic domain at the Cterminus [3,6]. The N-terminal transmembrane domain of the protein is thought to transport the acetyl donor, possibly acetylCoA, through the membrane [6].
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