MICROBIAL CONVERSION OF LONOPHOROUS ANTIBIOTIC NIGERICIN BY THE CILIATE TETRAHYMENA-PYRIFORMIS

The ionophorous antibiotic nigericin is toxic towards the ciliate Tetr ahymena pyriformis GL. At the high concentration of 30 mg/l (sublethal dose), it is bioconverted into several products. The yield of one of these (N1) is appreciably improved with pretreated cells, higher conce ntrations of nigericin (50 or 100 mg/l), and the presence of a larger ciliate biomass. A structural study of N1 by FAB mass spectrometry com bined with tandem mass spectrometry and nuclear magnetic resonance sho ws it to be an epimer, epinigericin, about half as toxic as nigericin. Bioconversion of nigericin by T. pyriformis may be regarded as a deto xication process.