Chemical and Ultrastructural Differences in Endotoxic Glycolipids from Salmonella Minnesota Re Mutant Extracted with Various Solvent Systems

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Abstract
Endotoxic glycolipids (ReGl) extracted from the whole cells (WC) and cell walls of heptose‐less Re mutant of Salmonella minnesota with hot phenol‐water (PW), phenol‐chloroform‐petroleum ether (PCP), and chloroform‐methanol (CM) were analyzed chemically and examined with an electron microscope. ReGl‐PW‐(WC) contained mannose and proteins as contaminants, ReGl‐PCP(WC) consisted of an excess amount of amino compound (cadaverine), and ReGl‐CM(WC) consisted of proteins and cadaverine, in addition to the ReGl constituents.The ultrastructure of ReGl‐PW(WC) resembled onions when stained with uranyl formate, and was spherical when stained with uranyl acetate, sodium phosphotungstate and ammonium molybdate, whereas those of ReGl‐PCP(WC) and ReGl‐CM(WC) were shaped like ribbons. However, the shadowed ultrastructures of ReGl‐PCP(WC) and ReGl‐CM(WC) showed small pieces of flat and wide sheets, respectively. ReGl‐PCP(WC) re‐extracted by the PW method was found to be converted into the onion‐like structure which was similar to that of ReGl‐PW(WC), while an intermediate form (fingerprint‐like) was observed after re‐extraction of ReGl‐PW(WC) with PCP. It was strongly suggested that the ultrastructural arrangement of ReGl was dependent on the solvent systems used for extraction.