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Microbiology
Table of Contents
Unit 5 Overview: The Eukaryotes of Microbiology
5.1 Unicellular Eukaryotic Parasites
5.2 Parasitic Helminths
5.3 Fungi
5.4 Algae
5.5 Lichens

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5.1 Unicellular Eukaryotic Parasites

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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 Parasite Characteristics and Taxonomy

Characteristics of unicellular eukaryotic parasites

  • Contain membrane-bound organelles such as a nucleus housing genetic material, mitochondria generating energy, and endoplasmic reticulum and Golgi apparatus synthesizing and transporting proteins
  • Unicellular organisms that live as parasites inside host organisms
  • Possess adaptations for a parasitic lifestyle including specialized structures for attaching to and invading host cells (adhesive discs in Giardia), mechanisms to evade host immune responses (antigenic variation in Trypanosoma), and the ability to obtain nutrients from the host (phagocytosis in Entamoeba)

Classification of unicellular eukaryotes

  • Diverse morphologies and life cycles historically made classification challenging
  • Molecular techniques and genetic sequencing, such as phylogenetic analyses of ribosomal RNA sequences and multigene analyses, have improved taxonomy by revealing more accurate evolutionary relationships
  • Currently classified based on morphological, biochemical, and molecular characteristics into major groups: Excavata (Giardia, Trichomonas, Trypanosoma), Chromalveolata (Plasmodium, Toxoplasma), Rhizaria, and Unikonta (Entamoeba)

Life Cycles, Infections, and Adaptations of Unicellular Eukaryotic Parasites

Life cycles of eukaryotic parasites

  • Involve multiple stages and hosts, alternating between sexual and asexual reproduction
  • Transmitted between hosts through various routes such as vector-borne (mosquitoes) or fecal-oral
  • Plasmodium (malaria) life cycle:
  1. Sporozoites injected by Anopheles mosquito infect liver cells and develop into merozoites
  2. Merozoites infect red blood cells, reproduce asexually, and release new merozoites
  3. Some merozoites differentiate into gametocytes, which are taken up by mosquito during blood meal
  4. Sexual reproduction occurs in mosquito midgut, and sporozoites migrate to salivary glands
  • Entamoeba histolytica life cycle: Fecal-oral transmission of cysts, excystation in small intestine, trophozoites colonize colon
  • Giardia lamblia life cycle: Fecal-oral transmission of cysts, excystation in small intestine, trophozoites attach to intestinal wall

Infections from eukaryotic parasites

  • Malaria (Plasmodium): Causes fever, anemia, and flu-like symptoms; severe cases can lead to organ failure and death; major global health burden, especially in sub-Saharan Africa
  • Amoebiasis (Entamoeba histolytica): Causes diarrhea, abdominal pain, and bloody stools; can cause liver abscesses; common in developing countries with poor sanitation
  • Giardiasis (Giardia lamblia): Causes diarrhea, abdominal cramps, and malabsorption; can lead to chronic infections; common waterborne infection worldwide
  • African sleeping sickness (Trypanosoma brucei): Causes fever, headache, and neurological symptoms; fatal if untreated; transmitted by tsetse flies in sub-Saharan Africa
  • Leishmaniasis (Leishmania): Causes cutaneous, mucocutaneous, or visceral manifestations depending on the species; transmitted by sandflies in tropical and subtropical regions

Adaptations for parasitism

  • Excavata (Giardia, Trichomonas, Trypanosoma) adaptations: Adhesive discs, hydrogenosomes, glycosomes, and variant surface glycoproteins
  • Chromalveolata (Plasmodium, Toxoplasma) adaptations: Apicoplast, rhoptries, micronemes, and antigenic variation
  • Unikonta (Entamoeba) adaptations: Amoeboid movement, cyst formation, and proteolytic enzymes
  • Attachment and invasion structures: Giardia's adhesive disc for attaching to intestinal wall, Plasmodium's apical complex (rhoptries and micronemes) for invading red blood cells
  • Nutrient acquisition: Trypanosoma's glycosomes for efficient glucose metabolism, Entamoeba's phagocytosis of bacteria and host cells
  • Immune evasion: Trypanosoma's variant surface glycoproteins for antigenic variation, Plasmodium's antigenic variation of PfEMP1 protein on infected red blood cell surface
  • Environmental resistance: Formation of cysts (Giardia, Entamoeba) or oocysts (Toxoplasma) for surviving outside the host

Host-Parasite Interactions and Disease Dynamics

Host-parasite interactions

  • Parasites evolve mechanisms to exploit host resources while hosts develop defenses, leading to an evolutionary arms race
  • Zoonotic transmission occurs when parasites jump from animal reservoirs to humans, often facilitated by close contact or environmental factors
  • Vector-borne diseases rely on arthropod vectors for transmission between hosts, complicating control efforts

Pathogenesis and epidemiology

  • Pathogenesis involves the mechanisms by which parasites cause disease, including direct tissue damage, toxin production, and immune-mediated pathology
  • Epidemiology studies the distribution, determinants, and control of parasitic diseases in populations, informing public health interventions and disease management strategies

Key Terms to Review (108)

African sleeping sickness: 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.
Algae: Algae are photosynthetic eukaryotic microorganisms found in various aquatic environments. They can be unicellular or multicellular, and play a crucial role in producing oxygen and serving as the base of many aquatic food webs.
Amoebic dysentery: Amoebic dysentery is a severe intestinal infection caused by the protozoan parasite Entamoeba histolytica. It leads to symptoms such as diarrhea, abdominal pain, and fever.
Amoebozoa: Amoebozoa is a phylum of unicellular eukaryotic organisms characterized by their amoeboid movement and shape-shifting abilities. They play significant roles in both free-living ecosystems and as parasites in various hosts.
Apicomplexans: Apicomplexans are a group of intracellular parasitic protozoans characterized by the presence of an apical complex, which aids in host cell invasion. They are known for causing significant diseases in humans and animals.
Apical complex: 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.
Balantidium coli: Balantidium coli is a unicellular, ciliated protozoan parasite that primarily infects the large intestine of humans and pigs. It is the only known ciliate parasite to infect humans.
Chagas disease: Chagas disease is a tropical parasitic illness caused by the protozoan Trypanosoma cruzi, primarily spread by triatomine bugs. It can lead to serious cardiac and digestive complications if untreated.
Chromalveolata: 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.
Ciliate: Ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia. These cilia are used for locomotion and feeding.
Cilia: Cilia are hair-like structures on the surface of eukaryotic cells that facilitate movement and sensory functions. They play vital roles in cell motility, fluid movement, and signaling.
Conjugation: Conjugation is a process where genetic material is transferred between bacterial cells through direct contact. It often involves the formation of a pilus to facilitate the exchange of plasmids.
Cryptosporidium parvum: Cryptosporidium parvum is a unicellular eukaryotic parasite that causes cryptosporidiosis, primarily affecting the intestines. It is known for its resilience in water and resistance to many conventional disinfection methods.
Contractile vacuole: A contractile vacuole is a specialized organelle in certain unicellular eukaryotes that expels excess water to maintain osmotic balance. It plays a crucial role in osmoregulation, especially in freshwater environments.
Cytoproct: A cytoproct is an excretory structure in certain unicellular eukaryotic organisms where waste materials are expelled from the cell. It functions similarly to an anus in multicellular organisms.
Cysticercosis: Cysticercosis is a parasitic tissue infection caused by the larval stage of the pork tapeworm, Taenia solium. It occurs when eggs are ingested and develop into cysticerci in tissues such as muscles, brain, and eyes.
Cytostome: A cytostome is a specialized cell structure in certain unicellular eukaryotic organisms, functioning as the cell's 'mouth.' It is involved in the ingestion of food particles.
Cyst: 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.
Dinoflagellates: Dinoflagellates are a group of unicellular eukaryotic organisms found in marine and freshwater environments. They can be photosynthetic, heterotrophic, or mixotrophic and are known for their two distinct flagella.
Diatoms: Diatoms are a major group of algae, specifically microalgae, characterized by their unique silica cell walls. They are found in oceans, freshwater, soils, and damp surfaces.
Dictyostelium discoideum: Dictyostelium discoideum is a species of soil-dwelling amoeba belonging to the group of cellular slime molds. It is commonly used as a model organism in molecular biology and genetics due to its unique life cycle and ease of cultivation.
Eimeria: Eimeria is a genus of unicellular eukaryotic parasites that primarily infect the intestines of various animals, causing coccidiosis. They belong to the phylum Apicomplexa and are known for their complex life cycles involving multiple stages.
Ectoplasm: Ectoplasm is the outer, more viscous region of the cytoplasm in certain unicellular eukaryotic organisms, such as protozoa. It plays a role in cell movement and shape maintenance.
Encystment: Encystment is the process by which a unicellular eukaryotic organism forms a cyst. This cyst acts as a protective barrier, allowing the organism to survive in unfavorable environmental conditions.
Endoplasm: Endoplasm is the inner, dense part of the cytoplasm in unicellular eukaryotic organisms. It plays a crucial role in cellular processes such as nutrient absorption and movement.
Euglena: Euglena is a genus of single-celled flagellate eukaryotes characterized by their ability to perform photosynthesis and heterotrophy. They are commonly found in freshwater environments.
Excavata: 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.
Eumycetozoa: Eumycetozoa, also known as slime molds, are a diverse group of single-celled eukaryotes that exhibit characteristics of both fungi and protozoa. They are primarily known for their unique life cycle stages, which include both unicellular and multicellular forms.
Flagella: Flagella are long, whip-like structures that protrude from the cell body of certain prokaryotic and eukaryotic cells. They are primarily used for locomotion and can also serve sensory functions.
Euglenozoa: Euglenozoa are a diverse group of unicellular eukaryotic organisms that include both free-living species and important parasites. They are characterized by the presence of a unique flagellum structure and a flexible pellicle.
Excystment: Excystment is the process by which a dormant cyst form of a microorganism, such as a protozoan, emerges into its active, vegetative state. This transition usually occurs in response to favorable environmental conditions.
Fornicata: Fornicata is a group of flagellated protozoan parasites within the supergroup Excavata. They are known for their unique feeding groove and lack of mitochondria, and include notable pathogens such as Giardia lamblia.
Fuligo septica: Fuligo septica, commonly known as the 'dog vomit' slime mold, is a plasmodial slime mold found in decaying wood and organic matter. It is notable for its bright yellow color and unique life cycle involving both single-celled and multicellular stages.
Giardia lamblia: 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.
Holozoic: Holozoic is a mode of nutrition where organisms ingest and internally digest solid food particles. It is characteristic of many unicellular eukaryotic parasites.
Hydrogenosomes: Hydrogenosomes are membrane-bound organelles found in certain anaerobic eukaryotic microorganisms that generate ATP. They produce hydrogen as a byproduct of their metabolic processes.
Irish potato famine: The Irish Potato Famine (1845-1852) was a period of mass starvation and disease in Ireland caused by the failure of the potato crop, which was heavily relied upon as a food source. The crop failure was due to an infection by the water mold Phytophthora infestans.
Ixodes scapularis: Ixodes scapularis, also known as the black-legged tick or deer tick, is a parasitic arachnid that primarily feeds on the blood of mammals, birds, and reptiles. It is a vector for several pathogens, including those causing Lyme disease and babesiosis.
Kinetoplastids: Kinetoplastids are a group of unicellular, flagellated eukaryotic organisms characterized by the presence of a kinetoplast, a unique structure containing condensed mitochondrial DNA. They are notable for including many parasitic species that cause significant human diseases.
Keratitis: Keratitis is the inflammation of the cornea, often caused by infections or injury. It can lead to pain, impaired vision, and if untreated, blindness.
Macronucleus: A macronucleus is a type of nucleus in certain unicellular eukaryotes, particularly ciliates, responsible for the regulation of non-reproductive cell functions. It controls everyday metabolic and developmental processes.
Microtubules: Microtubules are cylindrical structures composed of tubulin proteins that form part of the cytoskeleton in eukaryotic cells. They play critical roles in maintaining cell shape, enabling intracellular transport, and facilitating cell division.
Micronucleus: A micronucleus is a small, extra nucleus found in some unicellular eukaryotic organisms, playing a key role in reproductive and genetic processes. It usually contains a copy of the organism's genome and is involved in processes like conjugation.
Neglected parasitic infections (NPIs): Neglected parasitic infections (NPIs) are a group of parasitic diseases that are often overlooked by public health initiatives despite their significant impact on human health. They predominantly affect impoverished populations and can cause chronic illness and disability.
Opisthokonta: Opisthokonta is a broad, monophyletic group of eukaryotes characterized by cells with a single posterior flagellum. This group includes both fungi and animals, as well as some unicellular organisms.
Paramecium: Paramecium is a genus of unicellular ciliated protozoa commonly found in freshwater environments. They are characterized by their slipper-like shape and numerous hair-like structures called cilia.
Parabasalia: Parabasalia are a group of unicellular eukaryotic organisms within the supergroup Excavata. They are known for their symbiotic and parasitic relationships with various hosts, including humans.
Pellicle: A pellicle is a flexible, protective layer found just beneath the plasma membrane of certain unicellular eukaryotic organisms. It provides structural support and maintains cell shape while allowing some degree of flexibility.
Phytoplankton: Phytoplankton are microscopic, photosynthetic organisms found in aquatic environments. They form the base of the marine food web and play a crucial role in biogeochemical cycles, particularly carbon cycling.
Phytophthora: Phytophthora is a genus of plant-damaging oomycetes, known as water molds. These organisms are notorious for causing devastating plant diseases such as root rot and blight.
Plasmalemma: The plasmalemma, also known as the plasma membrane, is the outer boundary of a eukaryotic cell that regulates the movement of substances in and out of the cell. It consists of a lipid bilayer with embedded proteins that aid in various cellular functions.
Plasmodial slime molds: Plasmodial slime molds are unicellular eukaryotic organisms that exist as a large, multinucleate cell. They exhibit amoeboid movement and can form spore-producing structures under unfavorable conditions.
Plankton: Plankton are diverse collections of microscopic organisms that float or drift in water bodies. They play crucial roles in aquatic food webs and nutrient cycles.
Plasmodium: 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.
Polyphyletic: Polyphyletic refers to a group of organisms that are classified together but do not share an immediate common ancestor. This classification is based on convergent traits rather than genetic lineage.
Protist conjugation: Protist conjugation is a sexual reproduction process where two protists exchange genetic material through direct contact. This process enhances genetic diversity within the population.
Protists: Protists are a diverse group of unicellular eukaryotic microorganisms that can be free-living or parasitic. They inhabit various environments and exhibit a range of nutritional and reproductive strategies.
Protozoans: Protozoans are single-celled eukaryotic organisms often classified by their movement mechanisms. They can be free-living or parasitic and are found in various aquatic environments.
Pseudopodia: Pseudopodia are temporary, foot-like extensions of the cell membrane and cytoplasm used by some eukaryotic cells for movement and feeding. Commonly found in amoebas, pseudopodia enable these cells to change shape and navigate their environments.
Ringworm: Ringworm is a common fungal infection of the skin caused by dermatophytes. It presents as a red, circular rash with clearer skin in the middle.
Rhizaria: 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.
Saprozoic: Saprozoic organisms derive their nutrients through the absorption of dissolved organic material from their environment. They are often found in decaying matter and play a role in nutrient cycling.
Slime molds: Slime molds are eukaryotic organisms that can live freely as single cells but can aggregate to form multicellular reproductive structures. They are not true fungi but share some similarities in their life cycle and habitat.
Stentor: Stentor is a genus of unicellular eukaryotic protists, known for their trumpet-like shape and large size relative to other protozoa. Predominantly found in freshwater environments, they are notable for their cilia, which they use for feeding and locomotion.
Stigma: Stigma is a light-sensitive organelle found in certain unicellular eukaryotic organisms, such as algae and some protists. It helps the organism navigate toward light sources for photosynthesis.
Schizogony: Schizogony is a type of asexual reproduction in unicellular eukaryotic parasites where the nucleus divides multiple times before the cell splits into several daughter cells. This process is common in certain protozoans, such as Plasmodium species.
Supergroups: Supergroups are large, inclusive categories used to classify eukaryotes based on genetic and morphological similarities. They help organize the diversity of unicellular organisms into groups that share common ancestry.
Syngamy: Syngamy is the process of fusion between two gametes to form a zygote. It is a critical step in sexual reproduction among unicellular eukaryotic parasites.
Taenia solium: Taenia solium is a parasitic tapeworm primarily found in pigs and humans. It can cause neurocysticercosis, a serious nervous system infection.
Theileria (Babesia) microti: Theileria (Babesia) microti is a protozoan parasite that infects red blood cells and causes the disease babesiosis in humans. It is primarily transmitted through the bite of infected Ixodes scapularis ticks.
Toxoplasmosis: Toxoplasmosis is an infection caused by the unicellular eukaryotic parasite Toxoplasma gondii. It primarily affects the circulatory and lymphatic systems, often with mild symptoms in healthy individuals but can cause serious complications in immunocompromised patients and during pregnancy.
Toxocariasis: Toxocariasis is an infection caused by the larvae of Toxocara canis or Toxocara cati, which are parasitic roundworms typically found in dogs and cats. The condition primarily affects humans when they ingest infective eggs from contaminated soil or animal feces.
Trophozoite: A trophozoite is the active, feeding, and growing stage of a protozoan parasite. It contrasts with other life cycle stages such as cysts, which are dormant and resistant.
Trichomoniasis: Trichomoniasis is a sexually transmitted infection caused by the protozoan parasite Trichomonas vaginalis. It primarily affects the urogenital system, leading to symptoms such as itching, burning, and discharge.
Trypanosoma: Trypanosoma is a genus of unicellular parasitic protozoa. They are known for causing diseases such as African sleeping sickness and Chagas disease in humans.
Water molds: Water molds are filamentous, eukaryotic microorganisms that belong to the class Oomycetes. They thrive in aquatic environments and are known for causing plant diseases.
Wood’s lamp: Wood's lamp is a diagnostic tool that emits ultraviolet (UV) light to detect fungal and bacterial infections in the skin. It helps identify specific pathogens based on their fluorescence under UV light.
Zooplankton: Zooplankton are heterotrophic plankton that drift in aquatic environments. They include various unicellular eukaryotic organisms, many of which can be parasitic.
Trichomoniasis: Trichomoniasis is a sexually transmitted infection caused by the protozoan parasite Trichomonas vaginalis. It is a common urogenital infection that primarily affects the vagina, urethra, and prostate gland.
Giardiasis: 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.
Amoebae: Amoebae are single-celled eukaryotic organisms that belong to the kingdom Protista. They are characterized by their ability to change shape and move using temporary extensions of their cytoplasm called pseudopodia, which allow them to engulf and consume food particles.
Cyst: A cyst is a closed, membrane-bound structure that contains liquid, gaseous, or solid material. Cysts can develop in various parts of the body and are commonly associated with parasitic infections, particularly in the context of unicellular eukaryotic parasites, protozoan and helminthic infections of the skin and eyes, and protozoan infections of the gastrointestinal tract.
Monoxenous: Monoxenous refers to a parasite that requires only a single host species to complete its life cycle. These parasites are specialized to infect and reproduce within a specific host, without the need for an intermediate or secondary host.
Toxoplasma: 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.
Trophozoite: A trophozoite is the active, feeding, and replicating stage of a protozoan parasite that infects a host. It is the form of the parasite that is responsible for causing disease and symptoms in the infected individual.
Flagellates: Flagellates are a diverse group of unicellular eukaryotic organisms that possess one or more whip-like structures called flagella, which they use for locomotion and feeding. These protists are an important component of many ecosystems, including those related to 5.1 Unicellular Eukaryotic Parasites.
Ciliates: Ciliates are a group of eukaryotic, unicellular organisms characterized by the presence of hair-like structures called cilia on their cell surface. These cilia are used for locomotion, feeding, and other essential functions.
Heteroxenous: Heteroxenous refers to a type of parasitic life cycle where the parasite requires two or more different host organisms to complete its development. This term is particularly relevant in the context of unicellular eukaryotic parasites, as many of these organisms exhibit complex life cycles that involve multiple hosts.
Unikonta: 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.
Gametocytes: 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.
Glycosomes: 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.
Apicoplast: 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.
Leishmaniasis: 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.
Merozoites: 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.
African Sleeping Sickness: African sleeping sickness, also known as trypanosomiasis, is a parasitic disease caused by the protozoan Trypanosoma brucei, which is transmitted through the bite of an infected tsetse fly. It primarily affects individuals living in sub-Saharan Africa and can lead to severe neurological symptoms if left untreated.
PfEMP1: 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.
Sporozoites: 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.
Hydrogenosomes: Hydrogenosomes are organelles found in certain anaerobic eukaryotic microorganisms, such as unicellular parasites, that serve as the primary site of energy production in the absence of mitochondria. These specialized organelles are responsible for generating ATP through an anaerobic process involving the oxidation of hydrogen.
Pathogenesis: 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.
Antigenic Variation: 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.
Amoebiasis: 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.
Excystation: 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.
Rhoptries: 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.
Micronemes: 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.
Host-Parasite Interactions: Host-parasite interactions refer to the complex and dynamic relationship between a host organism and the parasitic organisms that live within or on it. This term is particularly relevant in the context of unicellular eukaryotic parasites, as these microscopic organisms rely on a host to survive and reproduce.
Zoonotic Transmission: 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.
Vector-Borne Diseases: 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.
Epidemiology: 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.