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EUKARYOTIC PARASITES.pptx
- 1. EUKARYOTIC DIVERSITY A REPORTON MICROBIOLOGY
- 2. UNICELLULAR EUKARYOTIC PARASITES Eukaryotic microbesare an extraordinarily diverse group, including species with a wide range of life cycles, morphological specializations, and nutritional needs. Although more diseases are caused by viruses and bacteria than by microscopic eukaryotes, these eukaryotes are responsible for some diseases of great public health importance.
- 3. UNICELLULAR EUKARYOTIC PARASITES For example,the protozoal disease malaria was responsible for 584,000 deaths worldwide (primarily children in Africa) in 2013, according to the World Health Organization (WHO). The protist parasite Giardia causes a diarrheal illness (giardiasis) that is easily transmitted through contaminated water supplies.
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- 5. PROTISTA Protozoans inhabit awide variety of habitats, both aquatic and terrestrial. Many are free-living, while others are parasitic, carrying out a life cycle within a host or hosts and potentially causing illness. There are also beneficial symbionts that provide metabolic services to their hosts. During the feeding and growth part of their life cycle, they are called trophozoites; these feed on small particulate food sources such as bacteria.
- 6. PROTISTA While some typesof protozoa exist exclusively in the trophozoite form, others can develop from trophozoite to an encapsulated cyst stage when environmental conditions are too harsh for the trophozoite. A cyst is a cell with a protective wall, and the process by which a trophozoite becomes a cyst is called encystment. When conditions become more favorable, these cysts are triggered by environmental cues to become active again through excystment.
- 7. PROTISTA Protozoans have avariety of reproductive mechanisms. Some protozoans reproduce asexually and others reproduce sexually; still others are capable of both sexual and asexual reproduction. In protozoans, asexual reproduction occurs by binary fission, budding, or schizogony. In schizogony, the nucleus of a cell divides multiple times before the cell divides into many smaller cells. The products of schizogony are called merozoites and they are stored in structures known as schizonts.
- 8. PROTISTA Many protists havewhip-like flagella or hair-like cilia made of microtubules that can be used for locomotion (Figure 4). Other protists use cytoplasmic extensions known as pseudopodia (“false feet”) to attach the cell to a surface; they then allow cytoplasm to flow into the extension, thus moving themselves forward.
- 9. PROTISTA Protozoans have avariety of unique organelles and sometimes lack organelles found in other cells. Some have contractile vacuoles, organelles that can be used to move water out of the cell for osmotic regulation (salt and water balance) (Figure 4). Mitochondria may be absent in parasites or altered to kinetoplastids (modified mitochondria) or hydrogenosomes.
- 10. PROTISTA AMOEBOZOA The supergroup Amoebozoa includes protozoansthat use amoeboid movement. Actin microfilaments produce pseudopodia, into which the remainder of the protoplasm flows, thereby moving the organism.
- 11. PROTISTA This deadly parasiteis found in warm, fresh water and causes primary amoebic meningoencephalitis (PAM). Another member of this group is Acanthamoeba, which can cause keratitis (corneal inflammation) and blindness.
- 12. PROTISTA The Eumycetozoa arean unusual group of organisms called slime molds, which have previously been classified as animals, fungi, and plants
- 13. PROTISTA CHROMALVEOLATA The supergroup Chromalveolata isunited by similar origins of its members’ plastids and includes the apicomplexans, ciliates, diatoms, and dinoflagellates, among other groups (we will cover the diatoms and dinoflagellates in Algae). The apicomplexans are intra- or extracellular parasites that have an apical complex at one end of the cell.
- 14. PROTISTA Chromalveolata The supergroup Chromalveolata isunited by similar origins of its members’ plastids and includes the apicomplexans, ciliates, diatoms, and dinoflagellates, among other groups (we will cover the diatoms and dinoflagellates in Algae). The apicomplexans are intra- or extracellular parasites that have an apical complex at one end of the cell.
- 15. PROTISTA Other apicomplexans arealso medically important. Cryptosporidium parvum causes intestinal symptoms and can cause epidemic diarrhea when the cysts contaminate drinking water. Theileria (Babesia) microti, transmitted by the tick Ixodes scapularis, causes recurring fever that can be fatal and is becoming a common transfusion- transmitted pathogen in the United States (Theileria and Babesia are closely related genera and there is some debate about the best classification).
- 16. PROTISTA Finally, Toxoplasma gondii causes toxoplasmosisand can be transmitted from cat feces, unwashed fruit and vegetables, or from undercooked meat. Because toxoplasmosis can be associated with serious birth defects, pregnant women need to be aware of this risk and use caution if they are exposed to the feces of potentially infected cats.
- 17. PROTISTA The ciliates (Ciliaphora), alsowithin the Chromalveolata, are a large, very diverse group characterized by the presence of cilia on their cell surface. Although the cilia may be used for locomotion, they are often used for feeding, as well, and some forms are nonmotile.
- 18. PROTISTA Balantidium coli (Figure 10)is the only parasitic ciliate that affects humans by causing intestinal illness, although it rarely causes serious medical issues except in the immunocompromised (those having a weakened immune
- 19. PROTISTA Öomycetes have similaritiesto fungi and were once classified with them. They are also called water molds. However, they differ from fungi in several important ways. Öomycetes have cell walls of cellulose (unlike the chitinous cell walls of fungi) and they are generally diploid, whereas the dominant life forms of fungi are typically haploid. Phytophthora, the plant pathogen found in the soil that caused the Irish potato famine, is classified within this group.
- 20. PROTISTA The group Excavataincludes the subgroups Fornicata, Parabasalia, and Euglenozoa. The Fornicata lack mitochondria but have flagella. This group includes Giardia lamblia (also known as G. intestinalis or G. duodenalis), a widespread pathogen that causes diarrheal illness and can be spread through cysts from feces that contaminate water supplies
- 21. PROTISTA The trichomonads (asubgroup of the Parabasalia) include pathogens such as Trichomonas vaginalis, which causes the human sexually transmitted disease trichomoniasis. Trichomoniasis often does not cause symptoms in men, but men are able to transmit the infection. In women, it causes vaginal discomfort and discharge and may cause complications in pregnancy if left untreated.
- 22. PROTISTA The Euglenozoa are commonin the environment and include photosynthetic and nonphotosynthetic species. Members of the genus Euglena are typically not pathogenic.
- 23. PROTISTA The Euglenozoa also includethe trypanosomes, which are parasitic pathogens. The genus Trypanosoma includes T. brucei, which causes African trypanosomiasis (African sleeping sickness and T. cruzi, which causes American trypanosomiasis (Chagas disease).
- 24. PROTISTA These tropical diseasesare spread by insect bites. In African sleeping sickness, T. brucei colonizes the blood and the brain after being transmitted via the bite of a tsetse fly (Glossina spp.) (Figure 15). The early symptoms include confusion, difficulty sleeping, and lack of coordination. Left untreated, it is fatal.
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- 27. PARASITIC HELMINTHS Parasitic helminthsare animals that are often included within the study of microbiology because many species of these worms are identified by their microscopic eggs and larvae. There are two major groups of parasitic helminths: the roundworms (Nematoda) and flatworms (Platyhelminthes). Of the many species that exist in these groups, about half are parasitic and some are important human pathogens.
- 28. PARASITIC HELMINTHS As animals,they are multicellular and have organ systems. However, the parasitic species often have limited digestive tracts, nervous systems, and locomotor abilities. Parasitic forms may have complex reproductive cycles with several different life stages and more than one type of host. Some are monoecious, having both male and female reproductive organs in a single individual, while others are dioecious, each having either male or female reproductive organs.
- 29. PARASITIC HELMINTHS NEMATODA These unsegmentedworms have a full digestive system even when parasitic. Some are common intestinal parasites, and their eggs can sometimes be identified in feces or around the anus of infected individuals. Ascaris lumbricoides is the largest nematode intestinal parasite found in humans; females may reach lengths greater than 1 meter.
- 30. PARASITIC HELMINTHS Of allnematode infections in the United States, pinworm (caused by Enterobius vermicularis) is the most common. Pinworm causes sleeplessness and itching around the anus, where the female worms lay their eggs during the night. Toxocara canis and T. cati are nematodes found in dogs and cats, respectively, that can be transmitted to humans, causing toxocariasis.
- 31. PARASITIC HELMINTHS Another commonnematode infection is hookworm, which is caused by Necator americanus (the New World or North American hookworm) and Ancylostoma duodenale (the Old World hookworm). Symptoms of hookworm infection can include abdominal pain, diarrhea, loss of appetite, weight loss, fatigue, and anemia.
- 32. PARASITIC HELMINTHS Trichinellosis, alsocalled trichinosis, caused by Trichinella spiralis, is contracted by consuming undercooked meat, which releases the larvae and allows them to encyst in muscles. Infection can cause fever, muscle pains, and digestive system problems; severe infections can lead to lack of coordination, breathing and heart problems, and even death.
- 33. PARASITIC HELMINTHS Finally, heartwormin dogs and other animals is caused by the nematode Dirofilaria immitis, which is transmitted by mosquitoes. Symptoms include fatigue and cough; when left untreated, death may result.
- 34. PARASITIC HELMINTHS FLATWORMS Phylum Platyhelminthes(the platyhelminths) are flatworms. This group includes the flukes, tapeworms, and the turbellarians, which include planarians. The flukes and tapeworms are medically important parasites (Figure 2).
- 35. PARASITIC HELMINTHS FLATWORMS Phylum Platyhelminthes(the platyhelminths) are flatworms. This group includes the flukes, tapeworms, and the turbellarians, which include planarians. The flukes and tapeworms are medically important parasites (Figure 2).
- 36. PARASITIC HELMINTHS The flukes(trematodes) are nonsegmented flatworms that have an oral sucker (Figure 3) (and sometimes a second ventral sucker) and attach to the inner walls of intestines, lungs, large blood vessels, or the liver. Trematodes have complex life cycles, often with multiple hosts. Several important examples are the liver flukes (Clonorchis and Opisthorchis), the intestinal fluke (Fasciolopsis buski), and the oriental lung fluke (Paragonimus westermani).
- 37. PARASITIC HELMINTHS Schistosomiasis isa serious parasitic disease, considered second in the scale of its impact on human populations only to malaria. The parasites Schistosoma mansoni, S. haematobium, and S. japonicum, which are found in freshwater snails, are responsible for schistosomiasis (Figure 4). Immature forms burrow through the skin into the blood. They migrate to the lungs, then to the liver and, later, other organs. Symptoms include anemia, malnutrition, fever, abdominal pain, fluid buildup, and sometimes death.
- 38. PARASITIC HELMINTHS The othermedically important group of platyhelminths are commonly known as tapeworms (cestodes) and are segmented flatworms that may have suckers or hooks at the scolex (head region) (Figure 3).
- 39. PARASITIC HELMINTHS Taenia saginata(the beef tapeworm) and T. solium (the pork tapeworm) enter humans through ingestion of undercooked, contaminated meat. The adult worms develop and reside in the intestine, but the larval stage may migrate and be found in other body locations such as skeletal and smooth muscle. The beef tapeworm is relatively benign, although it can cause digestive problems and, occasionally, allergic reactions.
- 40. PARASITIC HELMINTHS Taenia saginata(the beef tapeworm) and T. solium (the pork tapeworm) enter humans through ingestion of undercooked, contaminated meat. The adult worms develop and reside in the intestine, but the larval stage may migrate and be found in other body locations such as skeletal and smooth muscle. The beef tapeworm is relatively benign, although it can cause digestive problems and, occasionally, allergic reactions.
- 41. PARASITIC HELMINTHS Diphylobothrium latumis the largest human tapeworm and can be ingested in undercooked fish. It can grow to a length of 15 meters. Echinococcus granulosus, the dog tapeworm, can parasitize humans and uses dogs as an important host.
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- 43. FUNGI The fungi comprisea diverse group of organisms that are heterotrophic and typically saprozoic. In addition to the well-known macroscopic fungi (such as mushrooms and molds), many unicellular yeasts and spores of macroscopic fungi are microscopic. For this reason, fungi are included within the field of microbiology.
- 44. FUNGI Some pathogenic fungiare opportunistic, meaning that they mainly cause infections when the host’s immune defenses are compromised and do not normally cause illness in healthy individuals.
- 45. FUNGI They act asdecomposers in the environment, and they are critical for the production of certain foods such as cheeses. Fungi are also major sources of antibiotics, such as penicillin from the fungus Penicillium.
- 46. FUNGI Characteristics of Fungi Fungihave well-defined characteristics that set them apart from other organisms. Most multicellular fungal bodies, commonly called molds, are made up of filaments called hyphae.
- 47. FUNGI Hyphae can forma tangled network called a mycelium and form the thallus (body) of fleshy fungi. Hyphae that have walls between the cells are called septate hyphae; hyphae that lack walls and cell membranes between the cells are called nonseptate or coenocytic hyphae).
- 48. FUNGI In contrast tomolds, yeasts are unicellular fungi. The budding yeasts reproduce asexually by budding off a smaller daughter cell; the resulting cells may sometimes stick together as a short chain or pseudohypha (Figure 5.3.1 ). Candida albicans is a common yeast that forms pseudohyphae; it is associated with various infections in humans, including vaginal yeast infections, oral thrush, and candidiasis of the skin.
- 49. FUNGI Some fungi aredimorphic, having more than one appearance during their life cycle. These dimorphic fungi may be able to appear as yeasts or molds, which can be important for infectivity. They are capable of changing their appearance in response to environmental changes such as nutrient availability or fluctuations in temperature, growing as a mold, for example, at 25 °C (77 °F), and as yeast cells at 37 °C (98.6 °F).
- 50. FUNGI This ability helpsdimorphic fungi to survive in diverse environments. Histoplasma capsulatum, the pathogen that causes histoplasmosis, a lung infection, is an example of a dimorphic fungus.
- 51. FUNGI There are notableunique features in fungal cell walls and membranes. Fungal cell walls contain chitin, as opposed to the cellulose found in the cell walls of plants and many protists. Additionally, whereas animals have cholesterol in their cell membranes, fungal cell membranes have different sterols called ergosterols. Ergosterols are often exploited as targets for antifungal drugs.
- 52. FUNGI Fungal life cyclesare unique and complex. Fungi reproduce sexually either through cross- or self- fertilization. Haploid fungi form hyphae that have gametes at the tips.
- 53. FUNGI Two different matingtypes (represented as “+ type” and “– type”) are involved. The cytoplasms of the + and – type gametes fuse (in an event called plasmogamy), producing a cell with two distinct nuclei (a dikaryotic cell).
- 54. FUNGI Later, the nucleifuse (in an event called karyogamy) to create a diploid zygote. The zygote undergoes meiosis to form spores that germinate to start the haploid stage, which eventually creates more haploid mycelia (Figure 5.3.3 ).
- 55. FUNGI Depending on thetaxonomic group, these sexually produced spores are known as zygospores (in Zygomycota), ascospores (in Ascomycota), or basidiospores (in Basidiomycota).
- 56. FUNGI Depending on thetaxonomic group, these sexually produced spores are known as zygospores (in Zygomycota), ascospores (in Ascomycota), or basidiospores (in Basidiomycota).
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- 58. ALGAE The algae areautotrophic protists that can be unicellular or multicellular. These organisms are found in the supergroups Chromalveolata (dinoflagellates, diatoms, golden algae, and brown algae) and Archaeplastida (red algae and green algae). They are important ecologically and environmentally because they are responsible for the production of approximately 70% of the oxygen and organic matter in aquatic environments.
- 59. ALGAE Like protozoans, algaeoften have complex cell structures. For instance, algal cells can have one or more chloroplasts that contain structures called pyrenoids to synthesize and store starch. The chloroplasts themselves differ in their number of membranes, indicative of secondary or rare tertiary endosymbiotic events.
- 60. ALGAE Primary chloroplasts havetwo membranes—one from the original cyanobacteria that the ancestral eukaryotic cell engulfed, and one from the plasma membrane of the engulfing cell. Chloroplasts in some lineages appear to have resulted from secondary endosymbiosis, in which another cell engulfed a green or red algal cell that already had a primary chloroplast within it.
- 61. ALGAE The engulfing cell destroyedeverything except the chloroplast and possibly the cell membrane of its original cell, leaving three or four membranes around the chloroplast.
- 62. ALGAE Some algae, theseaweeds, are macroscopic and may be confused with plants. Seaweeds can be red, brown, or green, depending on their photosynthetic pigments. Green algae, in particular, share some important similarities with land plants; however, there are also important distinctions. For example, seaweeds do not have true tissues or organs like plants do.
- 63. ALGAE ALGAL DIVERSITY Although thealgae and protozoa were formerly separated taxonomically, they are now mixed into supergroups. The algae are classified within the Chromalveolata and the Archaeplastida.
- 64. ALGAE The dinoflagellates and stramenopilesfall within the Chromalveolata. The dinoflagellates are mostly marine organisms and are an important component of plankton.
- 65. ALGAE When a populationof dinoflagellates becomes particularly dense, a red tide (a type of harmful algal bloom) can occur. Red tides cause harm to marine life and to humans who consume contaminated marine life. Major toxin producers include Gonyaulax and Alexandrium, both of which cause paralytic shellfish poisoning.
- 66. ALGAE Another species, Pfiesteria piscicida,is known as a fish killer because, at certain parts of its life cycle, it can produce toxins harmful to fish and it appears to be responsible for a suite of symptoms, including memory loss and confusion, in humans exposed to water containing the species.
- 67. ALGAE The stramenopiles includethe golden algae (Chrysophyta), the brown algae (Phaeophyta), and the diatoms (Bacillariophyta). Stramenopiles have chlorophyll a, chlorophyll c1/c2, and fucoxanthin as photosynthetic pigments. Their storage carbohydrate is chrysolaminarin. While some lack cell walls, others have scales.
- 68. ALGAE Diatoms have flagellaand frustules, which are outer cell walls of crystallized silica; their fossilized remains are used to produce diatomaceous earth, which has a range of uses such as filtration and insulation. Additionally, diatoms can reproduce sexually or asexually. One diatom genus, Pseudo-nitzschia, is known to be associated with harmful algal blooms.
- 69. ALGAE The Archaeplastids include thegreen algae (Chlorophyta), the red algae (Rhodophyta), another group of green algae (Charophyta), and the land plants. The Charaphyta are the most similar to land plants because they share a mechanism of cell division and an important biochemical pathway, among other traits that the other groups do not have.
- 70. ALGAE Like land plants,the Charophyta and Chlorophyta have chlorophyll a and chlorophyll b as photosynthetic pigments, cellulose cell walls, and starch as a carbohydrate storage molecule. Chlamydomonas is a green alga that has a single large chloroplast, two flagella, and a stigma (eyespot); it is important in molecular biology research.
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- 72. LICHENS No one hasto worry about getting sick from a lichen infection, but lichens are interesting from a microbiological perspective and they are an important component of most terrestrial ecosystems. Lichens provide opportunities for study of close relationships between unrelated microorganisms. Lichens contribute to soil production by breaking down rock, and they are early colonizers in soilless environments such as lava flows.
- 73. LICHENS The cyanobacteria insome lichens can fix nitrogen and act as a nitrogen source in some environments. Lichens are also important soil stabilizers in some desert environments and they are an important winter food source for caribou and reindeer. Finally, lichens produce compounds that have antibacterial effects, and further research may discover compounds that are medically useful to humans.
- 74. LICHENS A lichen isa combination of two organisms, a green alga or cyanobacterium and an ascomycete fungus, living in a symbiotic relationship. Whereas algae normally grow only in aquatic or extremely moist environments, lichens can potentially be found on almost any surface (especially rocks) or as epiphytes (meaning that they grow on other plants).
- 75. LICHENS In some ways,the symbiotic relationship between lichens and algae seems like a mutualism (a relationship in which both organisms benefit). The fungus can obtain photosynthates from the algae or cyanobacterium and the algae or cyanobacterium can grow in a drier environment than it could otherwise tolerate.
- 76. LICHENS However, most scientistsconsider this symbiotic relationship to be a controlled parasitism (a relationship in which one organism benefits and the other is harmed) because the photosynthetic organism grows less well than it would without the fungus. It is important to note that such symbiotic interactions fall along a continuum between conflict and cooperation.
- 77. LICHENS Lichens have abody called a thallus, an outer, tightly packed fungal layer called a cortex, and an inner, loosely packed fungal layer called a medulla (Figure 1). Lichens use hyphal bundles called rhizines to attach to the substrate.
- 78. LICHENS Examples of thethree types of lichens are shown here. (a) This is a crustose lichen found mostly on marine rocks, Caloplaca marina. (b) This is a foliose lichen, Flavoparmelia caperata. (c) This is a fruticose lichen, Letharia vulpina, which is sufficiently poisonous that it was once used to make arrowheads. (credit b, c: modification of work by Jason Hollinger)