PHOSPHORYLATION OF LIPOPOLYSACCHARIDES IN THE ANTARCTIC PSYCHROTROPH PSEUDOMONAS-SYRINGAE - A POSSIBLE ROLE IN TEMPERATURE ADAPTATION

Phosphorylation of lipopolysaccharide (LPS) from a psychrotrophic bact erium, Pseudomonas syringae, from Antarctica was studied by using sucr ose gradient-separated membrane fractions. The bacterium was found to possess an LPS kinase which could phosphorylate more LPS postsynthetic ally at higher temperatures. The phosphorylation was low at a lower te mperature and was also found to occur in vivo. After phosphorylation o f LPS in vitro, it was found that the major part of the radioactivity (>85%) was associated with the core oligosaccharide region of the LPS. The phosphate groups of this region are probably involved in the bind ing of metal ions, which could be removed by E;DTA. The cells grown at the lower temperature probably contained fewer divalent cations becau se of the smaller amount of phosphate and thereby were more sensitive to EDTA. The cells were also more sensitive to cationic antibiotics at the lower temperature. A possible role of this differential phosphory lation of LPS in modulating the function of the outer membrane as a pe rmeability barrier in the psychrotroph is discussed.