LPS structure of Methylobacterium extorquens and its role in methanol resistance
Di Lorenzo, F.; Nicolardi, S.; Marchetti, R.; Vanacore, A.; Gallucci, N.; Duda, K.; Nieto Fabregat, F.; Nguyen, H. N. A.; Gully, D.; Sáenz, J.; Giraud, E.; Paduano, L.; Molinaro, A.; D’Errico, G.; Silipo, A. (2023) JACS Au, 3(3), 929–942. DOI: 10.1021/jacsau.3c00025
Summary
This study, led by Alba Silipo’s group (University of Naples), characterized the lipopolysaccharide (LPS) of [[methylobacterium-extorquens|Methylobacterium extorquens]], revealing a rough-type molecule with unusual structural features. The core oligosaccharide is non-phosphorylated and extensively O-methylated, with novel monosaccharide derivatives including O-methylated Kdo/Ko units. Lipid A has a non-phosphorylated trisaccharide backbone with a distinctive low acylation pattern — only three acyl chains plus a secondary very long chain fatty acid bearing a 3-O-acetyl-butyrate residue. Spectroscopic, conformational, and biophysical analyses demonstrated that these structural features regulate outer membrane molecular organization and improve membrane resistance to methanol.
Key Findings
- M. extorquens produces a rough-type LPS with an uncommon non-phosphorylated, extensively O-methylated core oligosaccharide
- Previously uncharacterized monosaccharide derivatives including O-methylated Kdo/Ko units were identified in the inner core region
- Lipid A has a non-phosphorylated trisaccharide backbone with atypically low acylation (three acyl chains plus one very long chain fatty acid)
- LPS structural features regulate lipid ordering and dynamics in the outer membrane
- These chemical features improve membrane resistance in the presence of methanol, contributing to methylotrophic capacity
Our Contribution
Our group contributed M. extorquens cultures, membrane biophysics expertise, and Ha Ngoc Anh Nguyen as a co-author on the biophysical characterization.
Significance
This work reveals how the outer membrane envelope of M. extorquens is chemically adapted for methanol tolerance, complementing our group’s findings on hopanoid-mediated lipid ordering in the outer membrane and lipidome adaptation in this organism.