Effects of Lead on the Lipid Compusition of Micrococcus luteus Cells

Steven L. Peterson, Larry G. Bennett, Thomas G. Tornabene
1975 Applied microbiology  
Micrococcus luteus cells cultivated in medium containing lead salts exhibited a sequence of changes in the quantity of total cellular lipids with essentially no changes from normal cellular yields. The lipid composition of cells cultivated one to four times was moderately decreased (phase I) whereas that of cells cultivated five to six times was reduced by as much as 50% (phase II). Cells cultivated more than six times in lead-containing media had progressively greater quantities of lipid
more » ... ties of lipid (phase HI) approaching that found in control cells. These cells with reestablished lipid contents showed no further effects from more prolonged exposure to lead salts. Chromatographic studies of total lipids of cells of each lipid phase revealed relatively complete lipid compositions. These results indicated that lead is apparently affecting a common biochemical parameter in the biosynthesis of lipids of lipid phase II cells. Changes in the relative quantities of individual components were observed in both the nonpolar and polar lipids in each lipid phase. The most notable changes were the decrease in aliphatic hydrocarbons with concomitant increases in the diglycerides and components identified as a complex family of ketones. Microscopy examinations of control and lead-treated cells revealed electron dense inclusion bodies in membrane fragments in only lead-treated cells. Previous studies in our laboratory (30, 31) have demonstrated that virtually all of the lead taken up by the bacterial cells was immobilized in the cellular envelope and associated largely with the cellular membrane. Investigations into the mechanisms of lead's immobilization and manifestation of toxicity in bacterial cells are completely lacking. Since specific lipids have been reported to form stable complexes with lead, usually under specific experimental conditions (11, 20, 38), it appears possible that the lipids of the membrane could have a role in the immobilization of lead and be a source of relatively small increments of lead transport to other parts of the cell. To determine the extent that lipids are involved, this paper describes the effects of lead on the total and individual membrane lipids of the natural skin bacterium Micrococcus luteus. The total lipid composition of the cells will be shown to be directly influenced by the presence of lead whereas essentially no differences are observed in culture yields. An accompanying paper describes in vitro studies on the interaction between specific lipids and lead.
doi:10.1128/aem.29.5.669-679.1975 fatcat:4x4bcgw4wrddbglvks7ytdioei