This picture shows a schematic view of the life cycle of P.carinii, a specific pathogen for human which caused Pneumocystis pneumonia as a form of pneumonia.
Two developmental stages are the mature cyst and the trophozoite. It is not yet clear which is the main infective form responsible for the primary infection. However, it is well established that airbone transmission is the most important
one.
Full description can be viewed here: http://www.scielo.br/pdf/mioc/v100n8/v100n8a13.pdf
yuk pneumonia would be bad