PURINE METABOLISM BY INTRACELLULAR CHLAMYDIA-PSITTACI

Purine metabolism was studied in the obligate intracellular bacterium Chlamydia psittaci AA Mp in the wild type and a variety of mutant host cell lines with well-defined deficiencies in purine metabolism. C. ps ittaci AA Mp cannot synthesize purines de novo, as assessed by its ina bility to incorporate exogenous glycine into nucleic acid purines. C. psittaci AA Mp can take ATP and GTP, but not dATP or dGTP, directly fr om the host cell. Exogenous hypoxanthine and inosine were not utilized by the parasite. In contrast, exogenous adenine, adenosine, and guani ne were directly salvaged by C. psittaci AA Mp. Crude extract prepared from highly purified C. psittaci AA Mp reticulate bodies contained ad enine and guanine but no hypoxanthine phosphoribosyltransferase activi ty. Adenosine kinase activity was detected, but guanosine kinase activ ity was not. There was no competition for incorporation into nucleic a cid between adenine and guanine, and high-performance liquid chromatog raphy profiles of radiolabelled nucleic acid nucleobases indicated tha t adenine, adenosine, and deoxyadenosine were incorporated only into a denine and that guanine, guanosine, and deoxyguanosine were incorporat ed only into guanine. Thus, there is no interconversion of nucleotides . Deoxyadenosine and deoxyguanosine were cleaved to adenine and guanin e before being utilized, and purine (deoxy)nucleoside phosphorylase ac tivity was present in reticulate body extract.