Long-term incorporation of tritiated adenine into deoxyribonucleic acid and ribonucleic acid by Treponema pallidum (Nichols strain)

Publisher Website
Google Scholar
Abstract
T. pallidum (Nichols strain), extracted in medium containing Eagle minimal essential medium, 50% fresh, heat-inactivated normal rabbit serum and 1.0 mM dithiothreitol, was incubated under 3% O2 in the presence of tritiated nucleic acid precursors. [8-3H]adenine was incorporated with high efficiency into trichloroacetic acid-insoluble material; 2''-deoxyadenosine and uridine were incorporated in lower quantities and thymine and thymidine were not incorporated. Incorporation of [3H]adenine was inhibited by penicillin G, mitomycin C, actinomycin D and erythromycin but was not affected by cycloheximide. Partial purification of nucleic acids from T. pallidum incubated with [8-3H]adenine for 36-72 h and subsequent treatment with RNase and DNase revealed that 15-20% of the trichloroacetic acid-precipitable counts were resistant to RNase but susceptible to DNase. A simple assay was developed in which NaOH treatment was used to distinguish incorporation into RNA and DNA. Both RNA and DNA synthesis continued for 6 days of incubation under 3% O2, incorporation was limited to the 1st day of incubation in samples incubated under aerobic or anaerobic conditions. T. pallidum thus appears to be capable of significant de novo DNA and RNA synthesis under microaerobic conditions.