Bucking the trend: understanding lipopolysaccharide structure and outer membrane dynamics in cold-adapted isolated from Enigma Lake, Antarctica

• Published in: Chemical science (Cambridge) 2024-11, Vol.15 (43), p.17852-17861
• Main Authors: Mercogliano, Marcello, De Chiara, Stefania, De Nicola, Antonio, Cardellini, Jacopo, Montis, Costanza, Yakimov, Mikhail M, La Cono, Violetta, Crisafi, Francesca, Silipo, Alba, Berti, Debora, Milano, Giuseppe, Molinaro, Antonio, Di Lorenzo, Flaviana
• Format: Article
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/d4sc05116e

Cold environments are predominant over the Earth and are inhabited by bacteria able to cope with a series of simultaneous environmental pressures. Gram-negative species of the Pseudomonas genus are the predominant ones isolated from cold habitats, making them an excellent model for studying the mechanisms of bacterial adaptation to the most extreme habitats on our planet. Here we focused on the lipopolysaccharide (LPS) structure and the outer membrane dynamics of Pseudomonas sp. EW#7, a strain isolated from Enigma Lake in Antarctica where, among other extreme characteristics, water temperature can reach 0.4 °C. We show that near-zero growth temperature mostly affects the LPS lipid A component. An uncommon tendency of decreasing lipid A secondary hydroxylation while increasing its phosphorylation degree was observed. This resulted in a faster lateral diffusion of lipid chains in the membrane and therefore in an enhancement of its fluctuations that guarantee membrane integrity and flexibility. Pseudomonas from Enigma Lake (Antarctica) has a peculiar lipopolysaccharide with an unusual tendency of decreasing lipid A secondary hydroxylation. This results in increased membrane fluidity that ensures bacterial survival at near-zero temperature.