DELETION MUTATIONS IN THE SPEED OPERON - SPERMIDINE IS NOT ESSENTIAL FOR THE GROWTH OF ESCHERICHIA-COLI

Null mutants of Escherichia coli were constructed that cannot synthesi ze spermidine. because of deletions in the gene encoding S-adenosylmet hionine decarboxylase. These mutants are still able to grow at near no rmal rates in purified media deficient in polyamines. These results in E. coli differ from recent findings that null mutants of Saccharomyce s cerevisiae and of Neurospora crassa have an absolute growth requirem ent for spermidine.