Peptidoglycan O-acetylation is functionally related to cell wall biosynthesis and cell division in Streptococcus pneumoniae.

The peptidoglycan is a rigid matrix required to resist turgor pressure and to maintain the cellular shape. It is formed by linear glycan chains composed of N-acetylmuramic acid-(ß-1,4)-N-acetylglucosamine (MurNAc-GlcNAc) disaccharides associated through cross-linked peptide stems. The peptidoglycan is continually remodelled by synthetic and hydrolytic enzymes and by chemical modifications, including O-acetylation of MurNAc residues that occurs in most Gram-positive and Gram-negative bacteria. This modification is a powerful strategy developed by pathogens to resist to lysozyme degradation and thus to escape from the host innate immune system but little is known about its physiological function. In this study, we have investigated to what extend peptidoglycan O-acetylation is involved in cell wall biosynthesis and cell division of Streptococcus pneumoniae. We show that O-acetylation driven by Adr protects the peptidoglycan of dividing cells from cleavage by the major autolysin LytA and occurs at the septal site. Our results support a function for Adr in the formation of robust and mature MurNAc O-acetylated peptidoglycan and infer its role in the division of the pneumococcus.

Distribution of wild bee (Hymenoptera: Anthophila) and hoverfly (Diptera: Syrphidae) communities within farms undergoing ecological transition.

BACKGROUND: In Havelange (Belgium), two farms are experiencing an ecological transition. We aimed to evaluate the impact of their agricultural activities on insect pollinator communities. This article depicts the situation at the very early stage of the farm transition. This study supports the fact that the maintenance of farm-level natural habitats provides environmental benefits, such as the conservation of two important pollinator communities: wild bees and hoverflies. NEW INFORMATION: Over two years (2018-2019), by using nets and coloured pan-traps, we collected 6301 bee and hoverfly specimens amongst contrasting habitats within two farmsteads undergoing ecological transition in Havelange (Belgium). We reported 101 bee species and morphospecies from 15 genera within six families and 31 hoverfly species and morphospecies from 18 genera. This list reinforces the national pollinator database by providing new distribution data for extinction-threatened species, such as Andrena schencki Morawitz 1866, Bombus campestris (Panzer 1801), Eucera longicornis (L.) and Halictus maculatus Smith 1848 or for data deficient species, such as A. semilaevis Pérez 1903, A. fulvata (Müller 1766), A. trimmerana (Kirby 1802) and Hylaeus brevicornis Nylander 1852.

One-Pot Two-Step Metabolic Labeling of Teichoic Acids and Direct Labeling of Peptidoglycan Reveals Tight Coordination of Both Polymers Inserted into Pneumococcus Cell Wall.

A method for labeling teichoic acids in the human pathogen Streptococcus pneumoniae has been developed using a one-pot two-step metabolic labeling approach. The essential nutriment choline modified with an azido-group was incorporated and exposed at the cell surface more rapidly than it reacted with the strain promoted azide alkyne cycloaddition (SPAAC) partner also present in the medium. Once at the cell surface on teichoic acids, coupling of the azido group could then occur within 5 min by the bio-orthogonal click reaction with a DIBO-linked fluorophore. This fast and easy method allowed pulse-chase experiments and was combined with another fluorescent labeling approach to compare the insertion of teichoic acids with peptidoglycan synthesis with unprecedented temporal resolution. It has revealed that teichoic acid and peptidoglycan processes are largely concomitant, but teichoic acid insertion persists later at the division site.