ABSTRACT
The phylum Ciliophora Doflein, 1901, includes highly evolved protozoa that propel their bodies and gather food by means of short hair-like projections called cilia, whose movement is coordinated in a rhythmical, metachronous (wave4ike) pattern. Cilia have a characteristic structurethe axoneme-consisting of nine pairs of microtubules surrounding an inner pair and anchored to the cell by a basal body, the kinetosome. The kinetosomes are interconnected by rows of fibrils called kinetodesmata that form extremely elaborate locomotor structures termed kineties. This internal system persists even when the cell is devoid of somatic cilia. A semi-rigid cortical pellicle functions as an exoskeleton, protecting and maintaining body shape. Ciliates are dikaryotic, with nuclear dimorphism: one or more polyploid vegetative macronuclei regulate the cell metabolism and have somatic functions, while one or more diploid micronucleirepository of the genomic DNA organized into chromosomes-are involved in the generative processes (Steinbrück, 1990; Lynn and Small,
They are generally amenable to culture in vitro on chemically defined media. The outcome of the dynamic interaction between these opportunistic pathogens and the compromised defense mechanisms of the host determines whether or not they succeed in invading deeper tissues and often causing lethal injuries.
