Is Longitudinal Division in Rod-Shaped Bacteria a Matter of Swapping Axis?

Tanneke Den Blaauwen

doi:10.3389/fmicb.2018.00822

Abstract

The morphology of bacterial species shows a wealth of variation from star-shaped to spherical and rod- to spiral-shaped, to mention a few. Their mode of growth and division is also very diverse and flexible ranging from polar growth and lateral surface increase to midcell expansion and from perpendicular to longitudinal asymmetric division. Gammaproteobacterial rod-shaped species such as Escherchia coli divide perpendicularly and grow in length, whereas the genetically very similar rod-shaped symbiotic Thiosymbion divide longitudinally, and some species even divide asynchronously while growing in width. The ovococcal Streptococcus pneumoniae also lengthens and divides perpendicularly, yet it is genetically very different from E. coli. Are these differences as dramatic as is suggested by visual inspection, or can they all be achieved by subtle variation in the regulation of the same protein complexes that synthesize the cell envelope? Most bacteria rely on the cytoskeletal polymer FtsZ to organize cell division, but only a subset of species use the actin homolog MreB for length growth, although some of them are morphologically not that different. Poles are usually negative determinant for cell division. Curved cell poles can be inert or active with respect to peptidoglycan synthesis, can localize chemotaxis and other sensing proteins or other bacterial equipment, such as pili, depending on the species. But what is actually the definition of a pole? This review discusses the possible common denominators for growth and division of distinct and similar bacterial species.

Highlights

Septum synthesis and cell division is initiated by a cytoskeletal protein, the tubulin homolog FtsZ
T. hypermnestrae the MreB inhibitor A22 completely abolished the synthesis of peptidoglycan as monitored by the lack of incorporation of fluorescent PG precursors (Figure 2; Pende et al, 2018)
T. oneisti, it is conceivable that MreB recruits FtsZ to the potential division site. Because these symbionts double in width predominantly by dividing (Pende et al, 2018), MreB might synthesize a band of preseptal PG and recruit FtsZ

Summary

Introduction

Bacteria can grow with a wealth of variations (Kysela et al, 2016) of which only the morphogenesis of the sphere, the ovococ, the rod-shape, and the crescent-shaped species have been thoroughly investigated in the form of Staphyloccocus aureus (Monteiro et al, 2015; Wheeler et al, 2015), Streptococcus pneumoniae (Morlot et al, 2003; Land and Winkler, 2011; Fleurie et al, 2014; Tsui et al, 2014; Bajaj et al, 2016), Escherichia coli (Egan et al, 2015; Blaauwen et al, 2017), Bacillus subtilis (Adams and Errington, 2009), and Caulobacter crescentus (Yakhnina and Gitai, 2013; Collier, 2016; Woldemeskel and Goley, 2017), respectively. Septum synthesis and cell division is initiated by a cytoskeletal protein, the tubulin homolog FtsZ. The longitudinal mode of division of the symbionts is supported by FtsZ, which forms an interrupted ellipse instead of a ring in Ca.T. oneisti (Leisch et al, 2012) and starts as an arc in the basal pole of Ca. T. hypermnestrae (Leisch et al, 2016; Figure 1A).

Results

Conclusion