title: The effect of penicillin on Chlamydia trachomatis DNA replication.
abstract: Chlamydia trachomatis L2 was used to infect BGMK cells at an m.o.i. of 1.0, and the developmental cycle was followed by transmission electron microscopy and quantitative PCR (QPCR) for both chromosomal and plasmid DNA. Samples were taken at sequential 6 h time points. Subsequent analysis by QPCR showed that there was an initial slow replication period (0-18 h), followed by a rapid phase (18-36 h) coinciding with exponential division when the DNA doubling time was 4.6 h. Chromosomal DNA was amplified 100-200-fold corresponding to 7-8 generations for the complete developmental cycle. Penicillin (10 and 100 units ml(-1)) was added to cultures at 20 h post-infection (p.i.). This blocked binary fission and also prevented reticulate body (RB) to elementary body transition. However, exposure to penicillin did not prevent chromosomal or plasmid DNA replication. After a short lag period, following the addition of penicillin, chlamydial chromosomal DNA replication resumed at the same rate as in control C. trachomatis-infected cells. C. trachomatis-infected host cells exposed to penicillin did not lyse, but instead harboured large, aberrant RBs in massive inclusions that completely filled the cell cytoplasm. In these RBs, the DNA continued to replicate well beyond the end of the normal developmental cycle. At 60 h p.i. each aberrant RB contained a minimum of 16 chromosomal copies.
authors.affiliation: Molecular Microbiology Group, University of Southampton Medical School, MP814, Southampton General Hospital, Hampshire SO16 6YD, UK.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Lambden
authors.affiliation: Molecular Microbiology Group, University of Southampton Medical School, MP814, Southampton General Hospital, Hampshire SO16 6YD, UK.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Pickett
authors.affiliation: Molecular Microbiology Group, University of Southampton Medical School, MP814, Southampton General Hospital, Hampshire SO16 6YD, UK.
authors.forename: Ian N
authors.initials: IN
authors.lastname: Clarke
mesh_terms: D000818:Animals; D002460:Cell Line; D002692:Chlamydia trachomatis / Q000187:drug effects* / Q000235:genetics* / Q000648:ultrastructure; D002522:Chlorocebus aethiops; D002876:Chromosomes, Bacterial / Q000235:genetics; D004261:DNA Replication / Q000187:drug effects* / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D002479:Inclusion Bodies / Q000648:ultrastructure; D007668:Kidney / Q000166:cytology; D010406:Penicillins / Q000494:pharmacology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D004269:DNA, Bacterial; D010406:Penicillins