. . "Bacteria and other prokaryotic organisms such as blue-green algae do not in general contain any of the conventional sterols found in plants and animals, but rather many species have related molecules, i.e. pentacyclic triterpenoids, based on a hopane skeleton with a cyclopentane E-ring and termed ???hopanoids??? (from the plant genus Hopea, from which they were isolated as components of the resin)" . .