PBP2b plays a key role in both peripheral growth and septum positioning in Lactococcus lactis

Abstract

Lactococcus lactis is an ovoid bacterium that forms filaments during planktonic and biofilm lifestyles by uncoupling cell division from cell elongation. In this work, we investigate the role of the leading peptidoglycan synthase PBP2b that is dedicated to cell elongation in ovococci. We show that the localization of a fluorescent derivative of PBP2b remains associated to the septal region and superimposed with structural changes of FtsZ during both vegetative growth and filamentation indicating that PBP2b remains intimately associated to the division machinery during the whole cell cycle. In addition, we show that PBP2b-negative cells of L. lactis are not only defective in peripheral growth; they are also affected in septum positioning. This septation defect does not simply result from the absence of the protein in the cell growth machinery since it is also observed when PBP2b-deficient cells are complemented by a catalytically inactive variant of PBP2b. Finally, we show that round cells resulting from β-lactam treatment are not altered in septation, suggesting that shape elongation as such is not a major determinant for selection of the division site. Altogether, we propose that the specific PBP2b transpeptidase activity at the septum plays an important role for tagging future division sites during L. lactis cell cycle.

Genes Contributing to the Unique Biology and Intrinsic Antibiotic Resistance of Enterococcus faecalis

“…As shown in Table 2 , insertional inactivation of PBPC and PBP2B is associated with a heavy fitness penalty under all conditions. PBP2B is known to be important for septum placement and elongation of ovococci ( 61 ) and is essential for the ovococcus S. pneumoniae ( 62 ). The low-affinity penicillin-binding protein PBP4 is central to the ability of E. faecalis to tolerate cephalosporins by a known structural mechanism ( 63 ), which is in turn regulated by the two-component system CroRS/HK-RR05 and the PASTA kinase IreK ( 64 ).…”

Organization of peptidoglycan synthesis in nodes and separate rings at different stages of cell division of Streptococcus pneumoniae

“…Whether the sPG and pPG synthesis machines of Spn are distributed contiguously in a single midcell ring (“plum pudding” model) or separate from each other during septal constriction has been a point of contention (David et al, 2018; Fleurie et al, 2014; Straume et al, 2016; Tsui et al, 2014). The demonstration of concentric intermediate rings of TP activity reported here provides strong support for the separation hypothesis (Figures 1d and 9a).…”

Organization of Peptidoglycan Synthesis in Nodes and Separate Rings at Different Stages of Cell Division ofStreptococcus pneumoniae

“…Whether the sPG and pPG synthesis machines of Spn are distributed contiguously in a single midcell ring (“plum pudding” model) or separate from each other during septal constriction has been a point of contention (11, 43–45). The demonstration of concentric intermediate rings of TP activity reported here provides strong support for the separation hypothesis (Fig.…”