The Pneumocystis life cycle

First recognised as "schizonts" of Trypanosoma cruzi, Pneumocystis organisms are now considered as part of an early-diverging lineage of Ascomycetes. As no robust long-term culture model is available, most data on the Pneumocystis cell cycle have stemmed from ultrastructural images of infected mammalian lungs. Although most fungi developing in animals do not complete a sexual cycle in vivo, Pneumocystis species constitute one of a few exceptions. Recently, the molecular identification of several key players in the fungal mating pathway has provided further evidence for the existence of conjugation and meiosis in Pneumocystisorganisms. Dynamic follow-up of stage-to-stage transition as well as studies of stage-specific proteins and/or genes would provide a better understanding of the still hypothetical Pneumocystislife cycle. Although difficult to achieve, stage purification seems a reasonable way forward in the absence of efficient culture systems. This mini-review provides a comprehensive overview of the historical milestones leading to the current knowledge available on the Pneumocystis life cycle.

Primary culture of intestinal epithelial cells as a potential model for Toxoplasma gondii enteric cycle studies

The primary culture of intestinal epithelial cells from domestic cats is an efficient cellular model to study the enteric cycle of Toxoplasma gondii in a definitive host. The parasite-host cell ratio can be pointed out as a decisive factor that determines the intracellular fate of bradyzoites forms. The development of the syncytial-like forms of T. gondii was observed using the 1:20 bradyzoite-host cell ratio, resulting in similar forms described in in vivo systems. This alternative study potentially opens up the field for investigation into the molecular aspects of this interaction. This can contribute to the development of new strategies for intervention of a main route by which toxoplasmosis spreads.