Bordetella bronchiseptica Glycosyltransferase Core Mutants Trigger Changes in Lipid A Structure

CASABUONO, ADRIANA C.; SISTI, FEDERICO; FERNÁNDEZ, JULIETA; HOZBOR, DANIELA; COUTO, ALICIA S.

JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY

ELSEVIER SCIENCE INC

Lugar: Amsterdam; Año: 2019

1044-0305

Bordetella bronchiseptica, known to infectanimals and rarely humans, expresses alipopolysaccharide that plays an essential role inhost interactions, being critical for early clearanceof the bacteria. On a B. bronchiseptica 9.73 isolate,mutants defective in the expression of genesinvolved in the biosynthesis of the core regionwere previously constructed. Herein, a comparativedetailed structural analysis of the expressedlipids A by MALDI-TOF mass spectrometry wasperformed. The Bb3394 LPS defective in a 2-amino-2-deoxy-D-galacturonic acid lateral residue of the corepresented a penta-acylated diglucosamine backbone modified with two glucosamine phosphates, similar to thewild-type lipid A. In contrast, BbLP39, resulting in the interruption of the LPS core oligosaccharide synthesis,presented lipid A species consisting in a diglucosamine backbone N-substituted with C14:0(3-O-C12:0) in C-2and C14:0(3-O-C14:0) in C-2′, O-acylated with C14:0(3-O-C10:0(3-OH) in C-3′ and with a pyrophosphate in C-1.Regarding Bb3398 also presenting a rough LPS, the lipid A is formed by a hexa-acylated diglucosaminebackbone carrying one pyrophosphate group in C-1 and one phosphate in C-4′, both substituted with ethanolaminegroups. As far as we know, this is the first description of a phosphoethanolamine modification inB. bronchiseptica lipid A. Our results demonstrate that although gene deletions were not directed to the lipid Amoiety, each mutant presented different modifications. MALDI-TOF mass spectrometry was an excellent tool tohighlight the structural diversity of the lipid A structures biosynthesized during its transit through the periplasm tothe final localization in the outer surface of the outer membrane.