Endotoxin structures in the psychrophiles Psychromonas marina and Psychrobacter cryohalolentis contain distinctive acyl features

• Published in: Marine drugs 2014-07, Vol.12 (7), p.4126-4147
• Main Authors: Sweet, Charles R, Alpuche, Giancarlo M, Landis, Corinne A, Sandman, Benjamin C
• Format: Article
• Language: English
• Subjects: Acinetobacter baumannii; Escherichia coli; Escherichia coli - chemistry; Gammaproteobacteria - chemistry; Gas Chromatography-Mass Spectrometry; lipid A; Lipid A - chemistry; lipid structure; lipopolysaccharide; Marine; mass spectrometry; Psychrobacter - chemistry; Psychrobacter cryohalolentis; psychrophile; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
• ISSN: 1660-3397; 1660-3397
• DOI: 10.3390/md12074126

Lipid A is the essential component of endotoxin (Gram-negative lipopolysaccharide), a potent immunostimulatory compound. As the outer surface of the outer membrane, the details of lipid A structure are crucial not only to bacterial pathogenesis but also to membrane integrity. This work characterizes the structure of lipid A in two psychrophiles, Psychromonas marina and Psychrobacter cryohalolentis, and also two mesophiles to which they are related using MALDI-TOF MS and fatty acid methyl ester (FAME) GC-MS. P. marina lipid A is strikingly similar to that of Escherichia coli in organization and total acyl size, but incorporates an unusual doubly unsaturated tetradecadienoyl acyl residue. P. cryohalolentis also shows structural organization similar to a closely related mesophile, Acinetobacter baumannii, however it has generally shorter acyl constituents and shows many acyl variants differing by single methylene (-CH2-) units, a characteristic it shares with the one previously reported psychrotolerant lipid A structure. This work is the first detailed structural characterization of lipid A from an obligate psychrophile and the second from a psychrotolerant species. It reveals distinctive structural features of psychrophilic lipid A in comparison to that of related mesophiles which suggest constitutive adaptations to maintain outer membrane fluidity in cold environments.