Metabolism of pyrimidine bases and nucleosides in Neisseria meningitidis

In Neisseria meningitidis, uridine, deoxyuridine, cytosine, cytidine, or deoxycytidine could not be used by uracil-requiring mutants as pyrimidine sources. Consistent with these findings, only 5-fluorouracil of the different fluoropyrimidine bases and nucleosides showed any inhibitory effect on the growth of four prototrophic strains of N. meningitidis. Likewise, only radioactive uracil was readily incorporated into nucleic acids, whereas uptake of radioactive uridine, cytosine, or cytidine could not be demonstrated. Uracil was converted to uridine 5'-monophosphate by uracil phosphoribosyltransferase, whereas enzyme activities for conversion of cytosine or any of the nucleosides were not detectable in meningococcal extracts.