A phylogenomic investigation of archaeal pseudomurein synthesis genes

Nika Pende, Simon Karl-Maria Rasso Rittmann, Silvia Bulgheresi, Simonetta Gribaldo

Archaea have structurally diverse cell walls. In most of them the cell wall is formed by a proteinaceous surface (S-) layer. However, in the two orders Methanopyrales and Methanobacteriales it consists of pseudomurein (or pseudo-peptidoglycan). Although archaeal pseudo-peptidoglycan (PG) is similar in overall structure to bacterial PG -both are mesh-like structures formed from linear chains of two alternating amino sugars -there are significant compositional differences. In bacterial PG, N-acetylmuramic acid is linked via a β-1,4 linkage to D-N-acetylglucosamine (GlcNAc), whereas archaeal pseudo-PG consists of L-N-acetyltalosaminuronic acid with a β-1,3 linkage to GlcNAc. Additionally, the D-amino acid interbridge is replaced by L-amino acids (glutamic acid, alanine and lysine). These structural differences make archaeal pseudo-PG resistant to b-lactam antibiotics, most lysozymes and proteases. Interestingly, thebiosynthetic pathway for pseudomurein synthesis was already proposed more than two decades ago based on biochemistry, but no archaeal homologs of bacterial PG synthesis and assembly proteins have been found so far. We carried out a detailed investigation of genes potentially participating in pseudo-PG synthesis in the 141 available genomes from Methanobacteriales and Methanopyrales. Through exhaustive searches of bacterial homologues, genome synteny exploration, and phylogenetic analysis, we were able to identify a few genes potentially engaged in archaeal pseudo-PG synthesis, as well as others possibly involved in cell growth and division. Some candidates will be tested experimentally in Methanobrevibacter smithii, a member of the Methanobacteriales commonly present in the gut of humans and other mammals.

Department für Ökogenomik und Systembiologie
Externe Organisation(en)
Institut Pasteur
ÖFOS 2012
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