Covers the phylum Ciliophora, describing typical ciliate habitats, lifestyles, cilia, dual nuclei, cell organelles and binary fission and conjugation. Focuses on Balantidium coli: its trophozoite and cyst forms, infection via contaminated food or water, pathogenicity in malnourished or immunocompromised people, and its life cycle. Includes recap questions and four mnemonics, one for the ciliate functions, one for the nuclei, one for the life cycle and one for symptoms.
Inside: 6 sections · 10 flashcards · 14 min
Topic 85 of 105 in the MU Sofia syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 4 sections, about 1,987 words (14 min of reading), with 10 flashcards.
In this note
Phylum Ciliophora. Balantidium coli
Recap Questions
Mnemonics
Metazoa: important evolutionary changes associated with the transition to multicellularity. Phylum Cnidaria (Coelenterata). Genus Hydra. Genus Obelia.
Phylum Ciliophora. Balantidium coli
Phylum Ciliophora (also known as Ciliata)
Members of this phylum are unicellular protozoa that are typically larger and more structurally complex than other protozoans.
Some ciliates can reach sizes up to 2 millimeters, making them visible to the naked eye in certain cases.
They inhabit a variety of aquatic environments, including:
Freshwater ecosystems such as lakes and ponds
Marine habitats such as oceans and estuaries
Moist terrestrial environments such as damp soils
Ciliates can live as:
Free-living organisms
Ectosymbionts that live on the surfaces of other organisms
Endosymbionts that reside within other organisms
Parasites, although parasitic forms are less common in this phylum
Key Structural Features of Ciliophora
A defining feature of ciliates is the presence of cilia, which are:
Short, hair-like projections covering all or part of the cell surface
Used for movement, feeding, attachment, and sensation
Structurally similar to flagella, but present in greater numbers and shorter in length
Ciliates have two types of nuclei:
A micronucleus, which is small and diploid, involved in genetic exchange and reproduction
A macronucleus, which is large and polyploid, responsible for metabolic and developmental control
The cell also contains:
A cytostome, which acts as a cell mouth for food intake
A cytopharynx, which channels food particles
Digestive vacuoles for intracellular digestion
Contractile vacuoles for expelling excess water
A cytoproct, which functions as the cell’s waste exit
Reproductive Processes in Ciliophora
Asexual reproduction takes place through binary fission, where the organism divides into two genetically identical cells.
Sexual reproduction occurs via a process called conjugation, which involves:
Two compatible ciliates joining temporarily
The exchange and fusion of haploid micronuclei
This process increases genetic diversity but does not immediately result in new offspring
Balantidium coli
Balantidium coli is the only known ciliate that infects humans and causes disease.
It primarily inhabits the caecum and colon of humans and certain animals including pigs, rats, and other mammals.
This organism is more commonly found in animals than in humans, and pigs are considered the primary reservoir.
Forms of Balantidium coli
The organism exists in two forms during its life cycle:
The trophozoite, which is the active, feeding form
Trophozoites are relatively large, measuring approximately 70 by 45 micrometers, but can grow up to 200 micrometers
The cyst, which is the dormant and infective stage
The cyst is characterized by a resistant wall, and it contains structures such as a macronucleus, micronucleus, contractile vacuole, and cilia
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