Abstract
As the 1st stage in investigating the genetic basis of natural variation in E. coli, the gene(s) conferring the ability to use sucrose as a C and energy source (given the symbol sac+) was transferred from a wild strain to K12, which does not use sucrose. The sac+ region was transferred by 2 different methods. On both occasions it took a chromosomal location at 50.5 min on the linkage map, between aroC and supN, in the region of the dsd genes, which confer the ability to use D-serine as a C and energy source. When the sac+ region was present in the K12 chromosome the bacteria were unable to use D-serine as a C and energy source. In F''sac+/dsd+ diploids, the dsd+ genes were similarly not expressed. Strain K12(sac+) bacteria were sensitive to inhibition by D-serine; they mutated to D-serine resistance with much greater frequency than did a dsd mutant of K12. Such bacteria also mutated frequently to use raffinose. Strain K12(sac+) bacteria did not utilize sucrose when they carried a mutation affecting the phosphotransferase system.