Design and application of a rapid screening technique for isolation of selenite reduction-deficient mutants of Shewanella putrefaciens.

A rapid screening technique for isolation of selenite (Se(IV)) reduction-deficient (Ser) mutants was developed and used to identify four Ser mutants of Shewanella putrefaciens. Two Ser mutants were unable to grow anaerobically on fumarate, nitrate or nitrite. Two other Ser mutants were unable to grow anaerobically on all compounds tested as sole terminal electron acceptor. Previously isolated Mn(IV) reduction-deficient mutants displayed Ser-positive phenotypes and reduced Se(IV) at wild-type rates, while two of nine Fe(III) reduction-deficient mutants displayed Ser-negative phenotypes and reduced Se(IV) at low rates. This study provides the first reported method for isolation of Ser mutants and demonstrates that Se(IV) reduction by S. putrefaciens is respiratory chain-linked.