The unusual cell wall of the Lyme disease spirochaete Borrelia burgdorferi is shaped by a tick sugar

Peptidoglycan—a mesh sac of glycans that are linked by peptides—is the main component of bacterial cell walls. Peptidoglycan provides structural strength, protects cells from osmotic pressure and contributes to shape. All bacterial glycans are repeating disaccharides of N-acetylglucosamine (GlcNAc) β-(1–4)-linked to N-acetylmuramic acid (MurNAc). Borrelia burgdorferi, the tick-borne Lyme disease pathogen, produces glycan chains in which MurNAc is occasionally replaced with an unknown sugar. Nuclear magnetic resonance, liquid chromatography–mass spectroscopy and genetic analyses show that B. burgdorferi produces glycans that contain GlcNAc–GlcNAc. This unusual disaccharide is chitobiose, a component of its chitinous tick vector. Mutant bacteria that are auxotrophic for chitobiose have altered morphology, reduced motility and cell envelope defects that probably result from producing peptidoglycan that is stiffer than that in wild-type bacteria. We propose that the peptidoglycan of B. burgdorferi probably evolved by adaptation to obligate parasitization of a tick vector, resulting in a biophysical cell-wall alteration to withstand the atypical torque associated with twisting motility.

Antibiofilm and Anti-candidal Activity of Extract of the Marine Sponge Agelas Dispar

This study aimed to determine the antifungal and antibiofilm activity of Agelas dispar on biofilm-producing of Candida species. Methanolic extract of A. dispar was obtained and the fraction Ag2 showed inhibitory activity for all the 13 Candida strains tested, in concentrations ranging from 2.5 mg/ml to 0.15625 mg/ml. Antifungal activity of fungicidal nature was seen between 5.0 mg/ml and 0.3125 mg/ml of extract against the strains. All strains were classified as biofilm producers. Methanolic extract Ag2 was tested at concentrations of 2.5 mg/ml and 1.25 mg/ml for antibiofilm activity against the biofilm in formation and mature biofilm from all the strains of the genus Candida. Treated and untreated biofilm samples were selected for visualization on Scanning Electron Microscopy (SEM). SEM allowed the visualization of the quantitative decrease of the microbial community, alterations of structural morphology and destruction, at the cellular level, in both forming and mature biofilm. It was suggested that the mechanism of action of the fraction is at a plasma membrane and/or cell wall alteration level. The fraction of methanolic extract of A. dispar may be a promising antifungal and antibiofilm therapeutic strategy against different species of the genus Candida.