Description and partial characterization of a new Chlamydia-like microorganism.

A new obligate intracellular bacterium which we called 'Z' was isolated as a cell culture contaminant of unknown origin. The organism grew in a variety of cultured cells with a 5-7-day developmental cycle, within cytoplasmic phagosomes, similarly to Chlamydia and some Rickettsia spp. Two alternating developmental forms (elementary bodies and reticulate bodies) were observed by electron microscopy. SDS-PAGE electrophoresis, immunoblotting with chlamydia-specific antibodies, and polymerase chain reaction using chlamydial genus specific primers provided evidence that our bacterium differs significantly from chlamydiae. Further characterization of 'Z' including determination of 16S ribosomal RNA sequences will allow its taxonomic position to be established.