Psychrophilic bacteria are adapted to grow and thrive at cold temperatures (less than 15°C), and are found frequently in marine environments, including in water and ice and in association with macroscopic marine organisms.  This work examines the chemical structure of lipid A, the essential structural element and hydrophobic anchor of lipopolysaccharide endotoxin, from Gram-negative psychrophilic marine bacteria.  As the outermost hydrophobic surface of these bacteria, lipid A is involved in bacterial interactions with and survival in its environment, and its structural details determine both immunological toxicity and membrane fluidity.  Previous work in our lab has revealed that lipid A is a structural scaffold for both constitutive and metabolic adaptation to cold growth conditions in arctic psychrophiles, utilizing shortened and unsaturated fatty acids that increase fluidity.  To refine understanding of this phenomenon and reveal possible systematic differences in structure and capability between arctic and temperate psychrophilic bacteria, we isolated environmental strains from the Saganavirktok and Kuparuk River watersheds of the Alaskan North Slope and also from winter surface water in a temperate estuary (Chesapeake Bay, MD USA).  Genetic identification by 16S sequencing and determination of growth kinetics under a range of temperature conditions were followed by analysis of endotoxin structure using chromatography and mass spectrometry, including MALDI-TOF MS and FAME GC-MS.  Preliminary data suggests that in both ecosystems a variety of evolutionary fluidity modulations are employed by these bacteria.  Structural variations largely follow taxonomic lines and include not only expected fluidity modifications but also changes to the phosphate structure of lipid A including addition of phosphoethanolamine.  This modification is commonly associated with immune evasion in pathogens, but could also decrease phosphate salt bridging in the membrane leading to an increase in fluidity.

Isolation of novel arctic and temperate marine psychrophiles and characterization of endotoxin structure

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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