A mutation affecting L-serine and energy metabolism in E. coli K12.

The effects of a pleiotropic mutation ssd are described. This mutation results in decreased efficiency in the use of glucose and fructose as carbon source, inability to use succinate or to grow anaerobically, an alteration in the activity of enzymes responsible for the synthesis and degradation of L-serine, increased resistance to certain antibiotics, and a deficiency in proline transport. This mutation resembles various previously described mutations thought to affect' energy coupling factor' and is located in the same region of the chromosome. While the gene product affected by this mutation is still unidentified, it is clear that L-serine metabolism cannot be understood merely in terms of providing L-serine and its derivatives.