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Keywords:

  • Bradyrhizobium;
  • gammacerane;
  • hopanoid;
  • tetrahymanol;
  • squalene

The nitrogen-fixing, symbiotic root-nodule forming bacterium Bradyrhizobium japonicum USDA 110 contained gammacerane derivatives next to triterpenoids of the hopane series. Diploptene, diplopterol, 2β-methyldiplopterol, aminobacteriohopanetriol and adenosylhopane were accompanied by tetrahymanol and the corresponding novel methylated homologues 2β-methyltetrahymanol, 20α-methyltetrahymanol, and 2β,20α-dimethyltetrahymanol. Incorporation of [2H3]methyl–l-methionine indicated that the additional methyl groups originated from methionine, probably with S-adenosylmethionine acting as methyl donor, with retention of the three deuterium atoms. The simultaneous presence of hopane and gammacerane derivatives seems a characteristic feature of the genus Bradyrhizobium and the phylogenetically closely related Rhodopseudomonas palustris.