PYRIMIDINE BIOSYNTHESIS IN PSEUDOMONAS-STUTZERI ATCC-17588

The de novo pyrimidine biosynthetic enzymes in the denitrifying bacter ium Pseudomonas stutzeri ATCC 17588 were assayed and their activities were lower in glucose-grown cells than in succinate-grown cells. When P. stutzeri was grown in the presence of uracil, the de novo enzyme ac tivities in succinate-grown cells were lowered while they remained lar gely unchanged in glucose-grown cells. A uracil auxotroph of P. stutze ri, deficient for aspartate transcarbamoylase activity, was isolated a nd its auxotrophic requirement was met by only uracil and cytosine. Th e inability of pyrimidine ribonucleosides to meet the auxotrophic requ irement was related to the limited ability of P. stutzeri to transport uridine and cytidine. Pyrimidine limitation of the auxotroph elevated the de novo enzyme activities indicating that this pathway may be rep ressible by a uracil-related compound in succinate-grown P. stutzeri c ells. Regulation of pyrimidine synthesis in P. stutzeri was similar to that observed for other pseudomonads classified within rRNA homology group I.