RESUMO
We previously reported that A. hydrophila GalU mutants were still able to produce UDP-glucose introduced as a glucose residue in their lipopolysaccharide core. In this study, we found the unique origin of this UDP-glucose from a branched α-glucan surface polysaccharide. This glucan, surface attached through the O-antigen ligase (WaaL), is common to the mesophilic Aeromonas strains tested. The Aeromonas glucan is produced by the action of the glycogen synthase (GlgA) and the UDP-Glc pyrophosphorylase (GlgC), the latter wrongly indicated as an ADP-Glc pyrophosphorylase in the Aeromonas genomes available. The Aeromonas glycogen synthase is able to react with UDP or ADP-glucose, which is not the case of E. coli glycogen synthase only reacting with ADP-glucose. The Aeromonas surface glucan has a role enhancing biofilm formation. Finally, for the first time to our knowledge, a clear preference on behalf of bacterial survival and pathogenesis is observed when choosing to produce one or other surface saccharide molecules to produce (lipopolysaccharide core or glucan).
Assuntos
Aeromonas/metabolismo , Proteínas de Bactérias/metabolismo , Glucanos/metabolismo , Ligases/metabolismo , Uridina Difosfato Glucose/metabolismo , Aeromonas/genética , Aeromonas/fisiologia , Aderência Bacteriana , Proteínas de Bactérias/genética , Biofilmes/crescimento & desenvolvimento , Sequência de Carboidratos , Linhagem Celular Tumoral , Eletroforese em Gel de Poliacrilamida , Teste de Complementação Genética , Glucanos/química , Glicogênio Sintase/genética , Glicogênio Sintase/metabolismo , Humanos , Ligases/genética , Lipopolissacarídeos/metabolismo , Viabilidade Microbiana , Dados de Sequência Molecular , Mutação , Antígenos O/metabolismo , UTP-Glucose-1-Fosfato Uridililtransferase/genética , UTP-Glucose-1-Fosfato Uridililtransferase/metabolismoRESUMO
The Aeromonas hydrophila AH-3 WecP represents a new class of UDP-HexNAc:polyprenol-P HexNAc-1-P transferases. These enzymes use a membrane-associated polyprenol phosphate acceptor (undecaprenyl phosphate [Und-P]) and a cytoplasmic UDP-d-N-acetylhexosamine sugar nucleotide as the donor substrate. Until now, all the WecA enzymes tested were able to transfer UDP-GlcNAc to the Und-P. In this study, we present in vitro and in vivo proofs that A. hydrophila AH-3 WecP transfers GalNAc to Und-P and is unable to transfer GlcNAc to the same enzyme substrate. The molecular topology of WecP is more similar to that of WbaP (UDP-Gal polyprenol-P transferase) than to that of WecA (UDP-GlcNAc polyprenol-P transferase). WecP is the first UDP-HexNAc:polyprenol-P GalNAc-1-P transferase described.
Assuntos
Aeromonas hydrophila/enzimologia , N-Acetilexosaminiltransferases/metabolismo , Fosfatos de Poli-Isoprenil/metabolismo , Uridina Difosfato N-Acetilgalactosamina/metabolismo , Sequência de Carboidratos , Modelos Moleculares , Dados de Sequência Molecular , N-Acetilexosaminiltransferases/químicaRESUMO
In this study, we report the identification of genes required for the biosynthesis of the core lipopolysaccharides (LPSs) of two strains of Proteus mirabilis. Since P. mirabilis and Klebsiella pneumoniae share a core LPS carbohydrate backbone extending up to the second outer-core residue, the functions of the common P. mirabilis genes was elucidated by genetic complementation studies using well-defined mutants of K. pneumoniae. The functions of strain-specific outer-core genes were identified by using as surrogate acceptors LPSs from two well-defined K. pneumoniae core LPS mutants. This approach allowed the identification of two new heptosyltransferases (WamA and WamC), a galactosyltransferase (WamB), and an N-acetylglucosaminyltransferase (WamD). In both strains, most of these genes were found in the so-called waa gene cluster, although one common core biosynthetic gene (wabO) was found outside this cluster.
