Final answer:
Balantidium coli is a trophozoite, the only parasitic ciliate that infects humans, often causing mild intestinal illness. It possesses cilia for movement and feeding, and has a unique nuclear setup with a micronucleus and macronucleus. B. coli contrasts with other parasites like Giardia lamblia and various tapeworms that have different infection mechanisms.
Step-by-step explanation:
The organism Balantidium coli is a trophozoite form isolated from the gut of a primate. This ciliate is notable for being the only protozoan parasite capable of infecting humans, specifically causing intestinal illness. B. coli is part of the Ciliophora, a diverse group whose members are characterized by the presence of cilia, which may be used for locomotion and feeding. The illness caused by B. coli is generally not serious except in individuals who are immunocompromised.
Within the ciliate group, the most well-known example is Paramecium, which is often studied in biology labs. Ciliates have unique nuclear machinery with both a micronucleus for sexual reproduction and a polyploid macronucleus for metabolic functions. In comparison to other protozoan parasites like Giardia lamblia that cause severe diarrhea, B. coli tends to have milder effects unless the individual has a weakened immune system.
It is important to distinguish B. coli from other intestinal parasites, such as tapeworms from the group of flatworms known as cestodes, which have a different mode of infection and life cycle involving intermediate hosts. Tapeworms can cause more serious health issues depending on the species and the site of infection.