High levels of glycolipid and low levels of phospholipid in a marine caulobacter

Abstract

Studies of the lipid composition of the marine bacterium Caulobacter halobacteroides revealed the presence of glycolipid as the predominant lipid constituent. The presence of minor amounts of phospholipid was confirmed with the incorporation of 14C- and 32P-labeled compounds. Other marine caulobacters had similar lipid compositions. Five chromatographically separable glycolipids were detected, two of which were identified as mono- and diglycosyldiglycerides. Glycolipid constituted 90 to 99% of the total extractable lipid based on 14C-acetate incorporation into six marine caulobacter strains. In addition, comparisons were made with the lipid extracts of the nonmarine Caulobacter crescentus and Micrococcus lysodeikticus, which contain substantial amounts of phospholipid. Studies of lipid composition during growth showed the maximum amount of phospholipid during early logarithmic growth (2.9%) with a decrease to 0.3% in the early stationary phase. The finding of a group of organisms in which phospholipid is not a major constituent of the lipid fraction is unique and generates many questions about the lipid requirements for membrane structure and function.