Distribution of Hopanoid Triterpenes in Prokaryotes

Pentacyclic triterpenoids of the hopane family were found in about half of some 100 strains of prokaryotes belonging to diverse taxonomic groups, such a wide distribution indicating the biological significance of these compounds. Hopanoids were found in almost all the cyanobacteria and obligate methylotrophs examined, in all the purple non-sulphur bacteria studied and in many taxonomically diverse Gram-negative or Gram-positive chemohetero-trophs. They were absent in all archaebacteria and purple sulphur bacteria examined as well as in various other Gram-positive or Gram-negative genera. The C30 hopanoids, diploptene and diplopterol, are present in almost all hopanoid-containing prokaryotes. The major compounds are always the C35 bacteriohopanepolyols, which are present at a level of 0.1-2 mg per g dry weight, the most common one being bacteriohopanetetrol. Because of their structural characteristics and their influence on the properties of biological membrane models, these compounds might be the structural equivalents of the sterols found in eukaryotes.