3 min read•Last Updated on June 18, 2024
Unicellular eukaryotic parasites are tiny but mighty troublemakers. They've got all the fancy cell parts like a nucleus and mitochondria, but they use them to freeload off other organisms. These sneaky little guys have evolved some clever tricks to survive inside hosts.
Scientists used to struggle to classify these diverse parasites, but new genetic tools have helped sort them out. Now we group them based on their looks, biochemistry, and DNA into categories like Excavata and Chromalveolata. Understanding their relationships helps us fight them better.
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
1 of 2
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
Unicellular Eukaryotic Parasites | Microbiology View original
Is this image relevant?
1 of 2
African sleeping sickness, also known as human African trypanosomiasis, is a parasitic disease caused by protozoa of the genus Trypanosoma. It is transmitted by the bite of an infected tsetse fly.
Term 1 of 108
African sleeping sickness, also known as human African trypanosomiasis, is a parasitic disease caused by protozoa of the genus Trypanosoma. It is transmitted by the bite of an infected tsetse fly.
Term 1 of 108
African sleeping sickness, also known as human African trypanosomiasis, is a parasitic disease caused by protozoa of the genus Trypanosoma. It is transmitted by the bite of an infected tsetse fly.
Term 1 of 108
Excavata is a major supergroup of unicellular eukaryotes characterized by their feeding groove, which is used to capture food. They include important parasitic species that affect humans and animals.
Giardia: A genus within the Excavata group known for causing gastrointestinal infections.
Trichomonas: A genus within the Excavata group known for causing sexually transmitted infections.
Flagella: Whip-like appendages used by some protists, including many in the Excavata group, for movement.
Chromalveolata is a major clade of eukaryotic organisms, primarily including certain algae and protists, characterized by the presence of alveoli structures beneath their cell membranes. This group includes important photosynthetic organisms and several pathogenic parasites.
Alveolate: A subgroup within Chromalveolata characterized by the presence of alveoli under their cell membranes.
Stramenopile: A subgroup within Chromalveolata known for having flagella with hair-like projections.
Plasmodium: A genus of parasitic protozoa within Chromalveolata responsible for causing malaria in humans.
Antigenic variation is the ability of pathogens, such as parasites and viruses, to alter their surface antigens or epitopes to evade the host's immune response. This process allows the pathogen to repeatedly infect the same host by presenting new antigenic targets, making it challenging for the immune system to mount an effective and lasting defense.
Epitope: The specific region on an antigen that is recognized and bound by antibodies or T-cell receptors, triggering an immune response.
Clonal Variation: The generation of genetically distinct subpopulations within a pathogen, each expressing different surface antigens.
Phase Variation: The reversible switching between the expression of different sets of surface antigens, allowing the pathogen to adapt to changing environmental conditions.
Trypanosoma is a genus of unicellular parasitic protozoa. They are known for causing diseases such as African sleeping sickness and Chagas disease in humans.
Protozoa: Single-celled eukaryotic organisms that can be free-living or parasitic.
Tsetse Fly: An insect vector responsible for transmitting Trypanosoma brucei, causing African sleeping sickness.
Chagas Disease: A disease caused by Trypanosoma cruzi, transmitted by triatomine bugs.
Plasmodium is a genus of unicellular eukaryotic parasites known to cause malaria in humans. These parasites are transmitted through the bite of infected Anopheles mosquitoes.
Malaria: A disease caused by Plasmodium parasites characterized by fever, chills, and anemia.
Anopheles mosquito: The primary vector responsible for transmitting Plasmodium parasites to humans.
Antimalarial drugs: Medications used to prevent or treat malaria infections caused by Plasmodium species.
Toxoplasma is a genus of obligate intracellular parasitic protozoa that can infect a wide range of warm-blooded animals, including humans. It is the causative agent of the disease toxoplasmosis, which can have serious consequences for certain populations, particularly pregnant women and individuals with compromised immune systems.
Toxoplasmosis: The disease caused by infection with the Toxoplasma parasite, which can lead to a range of symptoms and complications depending on the host's immune status.
Oocyst: The environmentally resistant stage of the Toxoplasma life cycle that is shed in the feces of infected cats, the definitive host for the parasite.
Bradyzoite: A slowly replicating stage of Toxoplasma that forms tissue cysts, allowing the parasite to persist in the host's body for long periods.
Rhizaria are a supergroup of mostly unicellular eukaryotes characterized by their amoeboid movement and the presence of complex shell structures. They are important in ecological roles such as nutrient cycling and as indicators in paleontological studies.
Foraminiferans: A group of Rhizaria known for their calcareous shells and significant role in marine sediments.
Radiolarians: A subgroup of Rhizaria with intricate silica-based skeletons, often found in oceanic plankton.
Cercozoans: Diverse group within Rhizaria that includes free-living and parasitic species with various feeding strategies.
Unikonta is a major group of eukaryotes that includes animals, fungi, and several protist lineages. The term 'unikonta' refers to the presence of a single flagellum or pseudopod during at least one stage of the organism's life cycle.
Opisthokonts: A clade of unikonts that includes animals, fungi, and closely related protist groups, characterized by a posterior flagellum or pseudopod.
Amoebozoa: A major group of unikonts that includes many amoeba-like protists, such as the common house amoeba.
Choanoflagellates: A group of free-living, aquatic unikont protists that are considered the closest living relatives of animals.
Sporozoites are the infective stage of certain parasitic protozoa, such as those that cause malaria and toxoplasmosis. They are the form of the parasite that is transmitted to a host, typically through the bite of an infected insect vector, and then invade the host's cells to initiate the parasitic life cycle.
Merozoites: Merozoites are the form of the parasite that multiplies within the host's cells, eventually rupturing the cells and invading new ones.
Gametocytes: Gametocytes are the sexual stage of the parasite that develop within the host's cells and are taken up by the insect vector during a blood meal, allowing the parasite to continue its life cycle.
Oocysts: Oocysts are the stage of the parasite that develops within the insect vector and eventually release the infective sporozoites.
Merozoites are the invasive stage of the malaria parasite that infects red blood cells during the asexual reproduction cycle. They play a crucial role in the pathogenesis of malaria, a parasitic infection that affects the circulatory and lymphatic systems.
Plasmodium: The genus of protozoan parasites that cause malaria in humans, with several species including P. falciparum, P. vivax, P. ovale, and P. malariae.
Erythrocytes: Red blood cells that are the target host cells for the Plasmodium merozoites during the asexual reproduction cycle.
Schizogony: The asexual replication process in the Plasmodium life cycle where merozoites are produced within the infected red blood cells.
Gametocytes are the sexual reproductive stages of certain unicellular eukaryotic parasites, such as those that cause malaria. They are responsible for the transmission of the parasite from the human host to the mosquito vector, enabling the continuation of the parasite's life cycle.
Sporozoites: The infective stage of malaria parasites that are injected into the human host by infected mosquitoes and initiate the infection.
Merozoites: The asexual reproductive stages of malaria parasites that invade and multiply within red blood cells.
Zygote: The diploid cell formed by the fusion of a male and female gamete, which develops into the ookinete stage in the mosquito.
Excystation is the process by which a dormant, encysted stage of a protozoan parasite emerges from its protective cyst to become an active, feeding trophozoite form. This process is a crucial part of the life cycle of many unicellular eukaryotic parasites and enables them to infect and proliferate within their host organisms.
Encystation: The process by which a protozoan parasite forms a protective cyst around itself, allowing it to survive in unfavorable environmental conditions.
Trophozoite: The active, feeding stage of a protozoan parasite that is capable of replicating and causing infection within the host.
Cyst: The dormant, environmentally resistant stage of a protozoan parasite that can survive outside of a host organism until conditions are favorable for excystation and infection.
Giardia lamblia is a unicellular eukaryotic parasite that causes giardiasis, a common gastrointestinal infection. It primarily inhabits the small intestine of humans and other mammals.
Cyst: A dormant form of certain parasites that allows survival in harsh conditions.
Trophozoite: The active, feeding stage in the life cycle of some protozoa.
Giardiasis: An infection caused by Giardia lamblia characterized by gastrointestinal symptoms.
Amoebiasis is a parasitic infection caused by the protozoan Entamoeba histolytica, which primarily affects the gastrointestinal tract. It is a significant public health concern, particularly in developing countries with poor sanitation and limited access to clean water.
Entamoeba histolytica: The pathogenic protozoan parasite that causes amoebiasis by infecting and damaging the human intestines and, in some cases, spreading to other organs.
Cyst: The dormant, infectious stage of Entamoeba histolytica that can survive outside the host and is responsible for the transmission of amoebiasis.
Trophozoite: The active, feeding stage of Entamoeba histolytica that can cause tissue damage and invasive disease within the human host.
Giardiasis is a parasitic infection caused by the protozoan parasite Giardia lamblia, which primarily affects the gastrointestinal tract. It is a common waterborne disease that can be transmitted through the ingestion of contaminated water or food, making it a significant public health concern.
Giardia lamblia: The protozoan parasite that causes giardiasis, also known as Giardia intestinalis or Giardia duodenalis. It is a flagellated, unicellular organism that can exist in two forms: a cyst and a trophozoite.
Waterborne Transmission: The mode of disease transmission where the Giardia parasite is spread through the ingestion of contaminated water, such as from untreated or improperly treated water sources.
Gastrointestinal Tract: The system of organs responsible for the digestion and absorption of food, which is the primary site of infection for the Giardia parasite in giardiasis.
African sleeping sickness, also known as human African trypanosomiasis, is a parasitic disease caused by protozoa of the genus Trypanosoma. It is transmitted by the bite of an infected tsetse fly.
Trypanosoma brucei: A parasitic protozoan species that causes African sleeping sickness.
Tsetse fly: A vector insect responsible for transmitting Trypanosoma parasites to humans.
Pentamidine: An antimicrobial drug used in the treatment of early-stage T. b. gambiense infection.
Leishmaniasis is a parasitic disease caused by Leishmania protozoa, which are transmitted to humans through the bite of infected sand flies. It is a significant public health concern, particularly in tropical and subtropical regions, and is classified as a neglected tropical disease. Leishmaniasis is closely associated with the topics of Unicellular Eukaryotic Parasites and Parasitic Infections of the Circulatory and Lymphatic Systems. The Leishmania parasites are unicellular eukaryotic organisms that infect and replicate within the host's immune cells, primarily macrophages. The disease can manifest in various forms, including cutaneous, mucocutaneous, and visceral leishmaniasis, depending on the species of Leishmania involved and the host's immune response.
Leishmania: The genus of protozoan parasites that cause leishmaniasis, including species such as Leishmania donovani, Leishmania major, and Leishmania braziliensis.
Sand Fly: The small, blood-feeding insect vector that transmits Leishmania parasites to humans and other mammalian hosts.
Macrophage: A type of immune cell that ingests and destroys foreign particles, bacteria, and other potentially harmful substances, including Leishmania parasites.
Hydrogenosomes are membrane-bound organelles found in certain anaerobic eukaryotic microorganisms that generate ATP. They produce hydrogen as a byproduct of their metabolic processes.
Mitochondria: Organelles responsible for ATP production through oxidative phosphorylation in aerobic eukaryotic cells.
Anaerobic Respiration: A form of respiration using electron acceptors other than oxygen.
Trichomonas vaginalis: A protozoan parasite known to contain hydrogenosomes and cause trichomoniasis in humans.
Glycosomes are specialized organelles found in certain unicellular eukaryotic parasites, such as trypanosomes and leishmania. They are responsible for compartmentalizing key metabolic processes, particularly those related to carbohydrate metabolism, within the parasite's cells.
Peroxisomes: Peroxisomes are membrane-bound organelles that play a role in various metabolic processes, including the breakdown of fatty acids and the detoxification of hydrogen peroxide.
Kinetoplast: The kinetoplast is a specialized DNA-containing structure found in the mitochondrion of trypanosomes and other related parasitic protozoa.
Trypanosoma: Trypanosoma is a genus of parasitic protozoa that are the causative agents of diseases such as African sleeping sickness and Chagas disease.
The apicoplast is a non-photosynthetic plastid organelle found in many apicomplexan parasites, including the causative agents of malaria, toxoplasmosis, and cryptosporidiosis. It is a remnant chloroplast-like structure that retains a small circular genome and is essential for the survival and proliferation of these parasites.
Apicomplexan: A phylum of single-celled eukaryotic parasites that includes the causative agents of malaria, toxoplasmosis, and cryptosporidiosis.
Plastid: A membrane-bound organelle found in plant and algal cells that is responsible for photosynthesis, storage, and other metabolic functions.
Chloroplast: A type of plastid found in the cells of plants and algae that is responsible for photosynthesis.
Rhoptries are specialized secretory organelles found in the apical complex of certain eukaryotic parasites, particularly those belonging to the phylum Apicomplexa. These organelles play a crucial role in the invasion and parasitism of host cells, making them an important feature of unicellular eukaryotic parasites.
Apical Complex: A specialized structure found at the apical (front) end of certain eukaryotic parasites, including the Apicomplexa, which contains various organelles like rhoptries, micronemes, and conoid that facilitate host cell invasion.
Micronemes: Secretory organelles found in the apical complex of Apicomplexa parasites that release proteins involved in the initial attachment and invasion of host cells.
Conoid: A cone-shaped structure found at the apical end of the Apicomplexa parasites that helps in the penetration and invasion of host cells.
Micronemes are specialized secretory organelles found in the apical region of unicellular eukaryotic parasites, such as those belonging to the Phylum Apicomplexa. These organelles play a crucial role in the initial attachment and invasion of host cells by these parasites during the infection process.
Apicomplexan Parasites: A group of obligate intracellular parasites that belong to the Phylum Apicomplexa, which includes well-known pathogens such as Plasmodium (the causative agent of malaria) and Toxoplasma.
Apical Complex: A specialized set of organelles found at the apical (anterior) end of apicomplexan parasites, which includes the micronemes, rhoptries, and other structures involved in host cell invasion.
Adhesins: Proteins found on the surface of micronemes that mediate the initial attachment of the parasite to the host cell surface, facilitating the invasion process.
A cyst is a dormant, resistant form of a unicellular eukaryotic organism that helps it survive harsh conditions. Cysts are often part of the life cycle of parasitic protozoa and can be involved in transmission to new hosts.
Trophozoite: The active, feeding stage of a protozoan life cycle.
Encystment: The process by which a trophozoite becomes a cyst.
Excystation: The process by which a cyst transforms back into an active trophozoite.
The apical complex is a specialized structure found in certain unicellular eukaryotic parasites, specifically those within the phylum Apicomplexa. It facilitates host cell invasion through a combination of secretory organelles and cytoskeletal elements.
Rhoptries: Organelles within the apical complex involved in secreting enzymes that facilitate host cell invasion.
Micronemes: Small secretory organelles in the apical complex that release proteins aiding parasite attachment to host cells.
Apicoplast: A non-photosynthetic plastid found in most Apicomplexa, crucial for fatty acid synthesis and other metabolic functions.
PfEMP1 (Plasmodium falciparum Erythrocyte Membrane Protein 1) is a key virulence factor expressed on the surface of red blood cells infected by the malaria parasite Plasmodium falciparum. It plays a crucial role in the pathogenesis of severe malaria by mediating the adhesion of infected red blood cells to the vascular endothelium, leading to complications such as cerebral malaria.
Cytoadhesion: The process by which infected red blood cells adhere to the vascular endothelium, leading to the obstruction of blood flow and the development of severe malaria complications.
Antigenic Variation: The ability of the malaria parasite to evade the host's immune system by constantly changing the expression of PfEMP1 proteins, making it difficult for the immune system to mount an effective response.
Rosetting: The formation of clusters of infected red blood cells around uninfected red blood cells, which can contribute to the obstruction of blood flow and the development of severe malaria.
Zoonotic transmission refers to the process by which infectious diseases are transmitted from animals to humans. This term is particularly relevant in the context of various microbiology topics, as it highlights the importance of understanding the complex interplay between different species and the potential for disease spread across the animal-human interface.
Zoonosis: A zoonosis is an infectious disease that can be transmitted from animals to humans, either through direct contact, indirect contact, or via a vector.
Reservoir Host: A reservoir host is an animal species that harbors a pathogen without showing signs of disease and can serve as a source of infection for other species, including humans.
Vector-Borne Transmission: Vector-borne transmission occurs when a vector, such as a mosquito or tick, acquires a pathogen from an infected animal and then transmits it to a human during a blood meal.
Vector-borne diseases are infectious diseases transmitted by the bite of infected arthropod species, such as mosquitoes, ticks, and fleas. These diseases are particularly relevant in the context of unicellular eukaryotic parasites and parasitic infections of the circulatory and lymphatic systems, as many of the causative agents are protozoan or helminthic parasites that rely on vectors for transmission between hosts.
Arthropod Vector: An arthropod, such as a mosquito, tick, or flea, that can transmit infectious pathogens from one host to another.
Zoonotic Diseases: Infectious diseases that can be transmitted from animals to humans, often through the involvement of a vector.
Pathogen Reservoir: A population or environment in which a pathogen can live, grow, and multiply, serving as a source for further infections.
Pathogenesis refers to the biological mechanisms by which a disease or disorder develops and progresses within a host organism. It encompasses the complex interplay between the pathogen and the host's immune system, leading to the manifestation of clinical symptoms and the establishment of the disease state.
Virulence Factors: Specific molecular components or mechanisms that enable a pathogen to cause harm or damage to the host, contributing to the pathogenesis of the disease.
Host-Pathogen Interactions: The dynamic interplay between the pathogen and the host's immune system, which can determine the outcome of the infection and the development of the disease.
Evasion of Host Defenses: The ability of a pathogen to circumvent or suppress the host's immune responses, allowing it to establish and propagate the infection, a crucial aspect of pathogenesis.
Epidemiology is the study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems. It is a fundamental science of public health that investigates the patterns, causes, and effects of diseases and other factors related to health in defined populations.
Incidence: The number of new cases of a disease or condition that develop in a population during a specific time period.
Prevalence: The total number of existing cases of a disease or condition in a population at a given time.
Morbidity: The state of being diseased or unhealthy within a population, often measured by the number of cases or the rate of a particular disease.