Squalenes, phytanes and other isoprenoids as major neutral lipids of methanogenic and thermoacidophilic “archaebacteria”

Abstract

The neutral lipids of nine species of methanogenic bacteria including five methanobacilli, two methanococci, a methanospirillum, one methanosarcina as well as two thermoacidophilic bacteria, Thermoplasma and Sulfolobus, were analyzed. The major components were C₃₀, C₂₅ and/or C₂₀ acyclic isoprenoid hydrocarbons with a continuous range of hydroisoprenoid homologues. The range of acyclic isoprenoids detected were from C₁₄ to C₃₀. Apart fromMetbanosarcina barkeri, squalene and/or hydrosqualene derivatives were the predominant components in all species studied. The components ofMetbanosarcina barkeri were a family of C₂₅ homologues. The distribution of the neutral lipid components and their specItIc variations in relative intensities emphasized the differences between the test organisms while the generic nature of the isoprenoid hydrocarbons demonstrated similarities between the diverse bacteria. The neutral lipid compositions from these bacteria, many of which exist in evironmental conditions like those described for the various evolutionary stages of the archean ecology, resemble the isoprenoid distribution isolated from ancient sediments and petroleum. Therefore, these findings may have major implications to biological and biogeochemical evolution.