Abstract
Peptidoglycan (PG) is essential for bacterial survival and maintaining cell shape. The rod-shaped model bacterium Escherichia coli has a set of seven endopeptidases that remodel the PG during cell growth. The gamma proteobacterium Candidatus Thiosymbion oneisti is also rod-shaped and attaches to the cuticle of its nematode host by one pole. It widens and divides by longitudinal fission using the canonical proteins MreB and FtsZ. The PG layer of Ca. T. oneisti has an unusually high peptide cross-linkage of 67% but relatively short glycan chains with an average length of 12 disaccharides. Curiously, it has only two predicted endopeptidases, MepA and PBP4. Cellular localization of symbiont PBP4 by fluorescently labeled antibodies reveals its polar localization and its accumulation at the constriction sites, suggesting that PBP4 is involved in PG biosynthesis during septum formation. Isolated symbiont PBP4 protein shows a different selectivity for β-lactams compared to its homologue from E. coli. Bocillin-FL binding by PBP4 is activated by some β-lactams, suggesting the presence of an allosteric binding site. Overall, our data point to a role of PBP4 in PG cleavage during the longitudinal cell division and to a PG that might have been adapted to the symbiotic lifestyle.
Highlights
Received: 30 January 2021Accepted: 6 March 2021Published: 9 March 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Licensee MDPI, Basel, Switzerland.This article is an open access articleThe growth mechanism of rod-shaped bacteria is one of best-studied, being exemplified by the Gram-negative and -positive model organisms Escherichia coli and Bacillus subtilis, respectively
We found that the PG composition of the symbiont deviated from far investigated gammaproteobacteria
T. oneisti has such a high-level of crosslinkage and how it is synthesized, we started to study PBPs that are responsible for PG construcand how it is synthesized, we started to study PBPs that are responsible for PG construction
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Candidatus Thiosymbion oneisti is an uncultivable rod-shaped ectosymbiont of the nematode host Laxus oneistus. It is a sulfur-oxidizing species that belongs to the Gramnegative Gammaproteobacteria like E. coli [1]. The PG layer is a covalently closed mesh made of glycan chains of β-linked Both growth diviand byby short peptides [5].[5]. The tubulin-like protein FtsZ assembles into filaments to form a ring at the at the prospective division site as the scaffold of divisome subunits [8]. PBPs with both transglycosylase activity—catalyzing theofelongation of glycan transpeptidase activity—crosslinking peptide bridges between chains—are chains—and transpeptidase activity—crosslinking peptideglycan bridges betweengrouped glycan into class A They are often essential for cell and survival, example, E. coli chains—are grouped into class.
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