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We have studied the usefulness of commercially available silica gel-containing tubes (serum separator tubes) for lipopolysaccharide extraction. Bacterial lipopolysaccharides from different bacterial species have been extracted in regular test tubes and tubes containing silica gel. They were characterized by chemical analysts, gel electrophoresis and enzyme linked immunosorbent assay, and one of their biological activities has been assayed. They were found to be indistinguishable, except that higher lipopolysaccharide yields were obtained when the extraction was carried out in silica gel-containing tubes. The use of these tubes provides a safe and convenient alternative to standard lipopolysaccharide extraction.

Bacteriophage FC3-9 is one of the several bacteriophages of Klebsiella pneumoniae C3 isolated in our laboratory. Mutants resistant to this bacteriophage were isolated and found to be devoid of lipopolysaccharide O antigen, modified in outer-membrane protein composition and sensitive to complement killing (serum-sensitive), unlike the wild-type strain. Serum-resistant mutants were isolated from these strains. They regained the lipopolysaccharide O antigen and the wild-type outer membrane protein composition and became sensitive to bacteriophage FC3-9.