The incorporation of 5-fluorouracil by Staphylococcus aureus (strain Duncan). II

• 1.

  1. The effects of 5-fluorouracil, not reversible in the presence of uracil, on Staphylococcus aureus (strain Duncan) were studied.

• 2.

  2. The logarithmic growth of S. aureus (strain Duncan) in the presence of 5-fluorouracil (100 μg/ml) and uracil (200 μg/ml) was retarded by 90% after 60-min incubation.

• 3.

  3. Up to 4% of the UMP in the ribosomal RNA was replaced during 60-min growth, by 5-fluorouracil ribotide: 14% of UMP in the soluble RNA was replaced during this period.

• 4.

  4. The proportions of cell wall, hexose and polysaccharide were unaffected, but the lipid content fell slightly.

• 5.

  5. Total nucleic acid fell by 45% but the total nitrogen (less nucleic acids) remained constant.

• 6.

  6. Continued incorporation of the analogue into soluble RNA was in contrast to its uptake into particulate RNA.

• 7.

  7. Acid-soluble protein from the cell sap showed marked changes in its electrophoretic characteristics.

• 8.

  8. It was concluded that protein synthesis was unabated, with the production of abnormal proteins caused by unnatural nucleic acids; and that ribosome synthesis was halted, although pre-existing ribosomes remained active.