Amphotericin B resistance is recessive in Chinese hamster hybrid cells

Previous studies from our laboratory have shown that Chinese hamster V79 cells mutated to high level resistance to amphotericin B have a lower cellular level of cholesterol, the target molecule for the polyene antibiotic. Two amphotericin B‐resistant (AMB R ) mutants were each hybridized to their parental amphotericin B‐sensitive (AMB S ) V79 cells. All the hybrids derived from AMB R /AMB S fusions were as sensitive to polyene antibiotics (amphotericin B, filipin, and pimaricin) as AMB S /AMB S hybrids. The AMB R /AMB S hybrids were found to contain cholesterol per phospholipids that is comparable to those in AMB S or AMB S /AMB S . The analysis of hybrids formed between mutant and wild‐type cells thus indicated that resistance to amphotericin B is a recessive marker, and that the cellular level of cholesterol is compensated in the AMB S /AMB R hybrids. Hybrids of AMB R and AMB R cells were all resistant, so that the three AMB R mutants all fell into a single complementation group.