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 synthesize spermidine, because of deletions in the gene encoding S-adenosylmethionine decarboxylase. These mutants are still able to grow at near normal rates in purified media deficient in polyamines. These results in E. coli differ from recent findings that null mutants of Saccharomyces cerevisiae and of Neurospora crassa have an absolute growth requirement for spermidine.