#archaeal cell wall

Microbial Physiology

Which glycosidic bond is found in the pseudomurein of archaea?

Glycosidic bond specificity determines susceptibility to host defenses and bacteriophages. Bacterial peptidoglycan uses beta-1,4 linkages between N-acetylglucosamine and N-acetylmuramic acid, a substrate efficiently cleaved by hen egg white lysozyme and human lysozyme in tears and mucus, which hydrolyzes between C1 of MurNAc and C4 of GlcNAc. Archaeal pseudomurein in methanogens such as Methanobacterium and Methanobrevibacter employs beta-1,3 linkage between N-acetylglucosamine and N-acetyltalosaminuronic acid. This change in linkage position alters orientation of sugar residues and active sit

Ref: Sekh et al., Extremophiles 2020, Pseudomurein Linkages; Leahy et al., Front Microbiol 2020, Archaeal Wall.

View Details

Microbial Physiology

In the pseudomurein layer, which sugar replaces N-acetylmuramic acid (NAM) found in bacterial peptidoglycan?

Pseudomurein represents fascinating case of convergent evolution where archaeal methanogens assemble wall polymer with superficial resemblance to bacterial peptidoglycan but distinct sugar composition rendering it insensitive to many antibacterial agents. In bacterial murein, alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) linked beta-1,4 carry lactyl ether with short peptide containing D-amino acids. Archaeal pseudomurein replaces NAM with N-acetyl-D-talosaminuronic acid, abbreviated NAT, which is N-acetylglucosamine epimer bearing carboxyl group at different position and

Ref: Kandler & Hippe, Arch Microbiol 1977, Pseudomurein Sacculus; Evren et al., J Bacteriol 2022, Pseudomurein Chemistry.

View Details

Microbial Physiology

Which polysaccharide is found in the archaeal cell wall instead of peptidoglycan?

Bacterial cell walls are built on peptidoglycan, a heteropolymer of N-acetylglucosamine and N-acetylmuramic acid crosslinked by peptide bridges sensitive to lysozyme and penicillin. Archaea do not synthesize peptidoglycan; instead, methanogenic euryarchaeota that possess a rigid wall produce pseudomurein, also called pseudopeptidoglycan, which superficially resembles peptidoglycan but differs chemically enough to confer resistance to classical wall antibiotics. Pseudomurein consists of N-acetylglucosamine linked to N-acetyltalosaminuronic acid rather than N-acetylmuramic acid, bearing L-amino

Ref: Albers & Meyer, Nature Rev Microbiol 2011, Pseudomurein; Kandler & Konig, Archaea 1998, Cell Walls.

View Details

Microbial Physiology

Which of the following is NOT a function of the S-layer in Archaea?

Archaeal S-layers are paracrystalline two-dimensional lattices of protein or glycoprotein that self-assemble to cover entire cell surface, often representing sole wall component outside cytoplasmic membrane in many species. These lattices provide robust protection against osmotic stress, mechanical disruption, predation by viruses, and low pH by acting as molecular sieve with defined pores around 2 to 8 nanometers that control passage of macromolecules, contributing to selective permeability. S-layer subunits also help determine and maintain cell shape, as seen in Halobacterium that loses rod

Ref: Albers & Meyer, Nature Rev Microbiol 2011, S-layers in Archaea; Ng et al., Front Microbiol 2013, Archaeal Cell Envelopes.

View Details