Chlamydia trachomatis is an important human pathogen which possesses a unique bi-phasic developmental cycle. We used lightcycler methodology to quantitatively measure gene transcript levels in C. trachomatis strain L2. By measuring 16S rRNA transcript levels, we determined C. trachomatis L2 to have a generation time of approximately 3 h and an inclusion burst size of 200^300 particles. The three chlamydial c c factor genes rpoD (c c 66 ), rpsD (c c 28 ) and rpoN (c c 54 ) exhibited different patterns of temporal expression. rpoD was central to early chlamydial development, whereas rpsD and rpoN were temporally expressed, coinciding with elementary body (EB) to reticulate body (RB) conversion and RB to EB conversion, respectively.z 1999 Federation of European Biochemical Societies.

The koala biovar of Chlamydia pneumoniae was identified in lung tissue from a sick, free-ranging giant barred frog (Mixophyes iteratus) by using electron microscopy, C. pneumoniae-specific fluorescent-antibody staining, cell culture, and sequencing of the ompA, ompB and 16S rRNA genes. This is the first report of a chlamydial strain infecting both a homeotherm and a poikilotherm and only the fourth host (in addition to humans, koalas, and horses) to be naturally infected with this species of Chlamydia. The frog had severe, chronic, mononuclear pneumonia and nonregenerative anemia and pancytopenia.

Immunization of female guinea pigs with a chimeric peptide consisting of variable domain IV (VDIV) and a region known as GP8 from the major outer membrane protein of Chlamydophila caviae, formerly Chlamydia psittaci guinea pig inclusion conjunctivitis strain, was performed to assess whether humoral immune responses could be elicited in the reproductive tracts of immunized animals. The C. caviae strain is able to cause a sexually transmitted infection in the guinea pig that closely parallels C. trachomatis infections in humans. The best anti‐VDIV antibody response in vaginal secretions was achieved by intraperitoneal priming with subsequent intravaginal boosting (P < 0.001). Dot‐blot analyses of vaginal secretions confirmed that these anti‐VDIV antibodies, produced against a linear peptide, were able to recognize and bind to whole conformational C. caviae elementary bodies. Following live intravaginal challenge with C. caviae, a significant reduction in the intensity (P = 0.01) and an apparent reduction in the duration of the infection was evident between the guinea pigs immunized with VDIV‐GP8 and non‐immunized controls.