Biosynthetic radiolabeling of bacterial lipopolysaccharide to high specific activity.

We describe a method for producing radiolabeled lipopolysaccharide (LPS) by incorporating [3H]acetate into an aceEF, gltA strain of Escherichia coli K12. The LPS has substantially greater specific radioactivity (2 microCi per microgram LPS, or approximately 8 Ci/mmol) than has been reported previously for biosynthetically radiolabeled LPS. The 3H is incorporated into the fatty acyl chains of the lipid A moiety. LPS prepared by this method has several attractive features for biological studies, including native structure and bioactivity, long radioactive half-life, and high specific activity.