SEDS–bPBP pairs direct lateral and septal peptidoglycan synthesis in Staphylococcus aureus

Abstract

Peptidoglycan (PGN) is the major component of the bacterial cell wall, a structure essential for the physical integrity and shape of the cell. Bacteria maintain cell shape by directing PGN incorporation to distinct regions of the cell, namely through the localisation of the late stage PGN synthesis proteins. These include two key protein families, SEDS transglycosylases and the bPBP transpeptidases, proposed to function in cognate pairs. Rod-shaped bacteria have two SEDS-bPBP pairs, involved in cell elongation and cell division. Here, we elucidate why coccoid bacteria, such as Staphylococcus aureus, also possess two SEDS-bPBP pairs. We determined that S. aureus RodA-PBP3 and FtsW-PBP1 likely constitute cognate pairs of interacting proteins. Lack of RodA-PBP3 decreased cell eccentricity due to deficient pre-septal PGN synthesis, whereas the depletion of FtsW-PBP1 arrested normal septal PGN incorporation. Although PBP1 is an essential protein, a mutant lacking PBP1 transpeptidase activity is viable, showing that this protein has a second function. We propose that the FtsW-PBP1 pair has a role in stabilising the divisome at midcell. In the absence of these proteins, the divisome appears as multiple rings/arcs that drive lateral PGN incorporation, leading to cell elongation. We conclude that RodA-PBP3 and FtsW-PBP1 mediate lateral and septal PGN incorporation, respectively, and that the activity of these pairs must be balanced in order to maintain coccoid morphology. Peptidoglycan (PGN) synthesis is an essential process that is both spatially and temporally regulated to ensure that the bacterial cell shape is maintained 1 . Rod-shaped bacteria elongate by synthesising PGN along the length of the cell in a process directed by the cytoskeletal protein MreB 2 . In Escherichia coli and Bacillus subtilis, this protein polymerises into short filaments that move processively around the cell diameter, and organise a multi-protein machinery, including PGN synthesis proteins, referred to as the elongasome or the Rod system [3][4][5] . Cell division is dependent on another cytoskeletal protein, FtsZ, which polymerises to form the Z-ring and recruits a multi-protein complex responsible for septum synthesis, known as the divisome 6,7 . This complex directs PGN incorporation to the midcell, resulting in inward PGN synthesis, and eventually bisects the mother cell, leading to daughter cell separation.Ovococci such as Streptococcus pneumoniae and Lactococcus lactis lack MreB, and FtsZ is proposed to coordinate both elongation and septation 8,9 . In these organisms PGN is

Cell Shape and Antibiotic Resistance Are Maintained by the Activity of Multiple FtsW and RodA Enzymes in Listeria monocytogenes

“…Previous studies have shown that members of the SEDS protein family act together with a cognate class B PBP to synthesize and cross-link peptidoglycan (28, 34, 56–58). L.…”

“…subtilis, and S. aureus (28, 35, 36, 39, 43). Our experiments suggested that FtsW1 is also essential in L.…”

“…Recently, it was shown that RodA-PBP3 and FtsW-PBP1 act as cognate pairs in the coccoid bacterium S. aureus (28). Depletion of all three RodA enzymes in L.…”

“…Recently, it has been shown that members of the SEDS (shape, elongation, division, sporulation) family of proteins, namely, RodA and FtsW, also act as glycosyltransferases (22–25). Both RodA and FtsW form complexes with cognate class B PBPs to enable polymerization and cross-linking of glycan strands (23, 25–28). Interestingly, SEDS proteins and the class B PBPs are more conserved among different bacterial species than class A PBPs are (22).…”

The evolution of spherical cell shape; progress and perspective

“…However, it is now known that even S. aureus still undergoes some elongation through the action RodA–PBP3, which are elongasome-associated proteins. Reichmann et al [117] demonstrated that the loss of RodA–PBP3 results in even more spherical S. aureus cells.…”