The different shapes of cocci

Abstract

The shape of bacteria is determined by their cell wall and can be very diverse. Even among genera with the suffix 'cocci', which are the focus of this review, different shapes exist. While staphylococci or Neisseria cells, for example, are truly round-shaped, streptococci, lactococci or enterococci have an ovoid shape. Interestingly, there seems to be a correlation between the shape of an organism and its set of penicillin-binding proteins--the enzymes that assemble the peptidoglycan, the main constituent of the cell wall. While only one peptidoglycan biosynthesis machinery seems to exist in staphylococci, two of these machineries are proposed to function in ovoid-shaped bacteria, reinforcing the intrinsic differences regarding the morphogenesis of different classes of cocci. The present review aims to integrate older ultra-structural data with recent localization studies, in order to clarify the relation between the mechanisms of cell wall synthesis and the determination of cell shape in various cocci.

Control of cell division in Streptococcus pneumoniae by the conserved Ser/Thr protein kinase StkP

“…2A). To verify efficient production of the fusion proteins and the absence of protein degradation, wild-type strains carrying the P Zn -gfp-kinase, P Zn -gfp-kinase-TM, and P Zngfp-TM-PASTA fusions were grown and induced with 0.15 mM ZnSO 4 , and cells were harvested at midexponential phase for Western blot analysis using anti-GFP polyclonal antibodies and for fluorescence microscopy. As shown in Fig.…”

“…S3) and inserted it in the D39, R6, and Rx1 genetic backgrounds. Wild-type strains carrying the gfp-phpP fusion were grown to midexponential phase, induced with 0.15 mM ZnSO 4 , and cells were analyzed by fluorescence microscopy. As shown in Fig.…”

“…Although recently substantial progress has been made in understanding the molecular mechanisms that govern S. pneumoniae cell division (for a review, see ref. 4), the molecular mechanisms involved in the earlier events of the cell cycle, and what controls them, are largely unknown. In particular, what is not understood is how S. pneumoniae coordinates peripheral and septal cell-wall synthesis, by sensing the morphological changes that occur during growth and division, to achieve proper shape.…”

The function of the transmembrane and cytoplasmic domains of pneumococcal penicillin-binding proteins 2x and 2b extends beyond that of simple anchoring devices

“…This implies that PBP2x and PBP2b serve, at least in part, different functions. Available evidence suggests strongly that PBP2x is indispensable for the synthesis of the septal crosswall, while PBP2b is dedicated to peripheral peptidoglycan synthesis Morlot et al, 2003;Peters et al, 2014;Zapun et al, 2008). PBP2x consists of an N-terminal cytoplasmic tail of about 27 aa, a single membrane-spanning segment and three extracellular domains.…”

“…The last-named process involves the so-called penicillin-binding proteins (PBPs). The PBPs produced by Streptococcus pneumoniae fall into three classes: the bifunctional class A PBPs (PBP1a, PBP2a and PBP1b) that possess transglycosylase as well as transpeptidase activities, the monofunctional class B PBPs (PBP2x and PBP2b) which function as transpeptidases, and the low-molecular-mass carboxypeptidase DacA (Massidda et al, 2013;Sauvage et al, 2008;Zapun et al, 2008). In contrast to the three class A PBPs, which can be individually deleted, both class B PBPs of S. pneumoniae are essential (Kell et al, 1993;Paik et al, 1999).…”