Microbiology Chapter 12

What are five different kinds of asexual spores?

-Conidiospore, or conidium, a unicellular or multicellurlar spore that is not enclosed in a sac. Conidia are produced in a chain at the end of a conidiophore. Conidia formed by the fragmentation of septate hypha into single, slightly thickened cells are called arthroconidia. Another type of conidium, blastoconidia, consists of buds coming off the parent cell. A chlamydoconidium is a thick-walled spore formed by rounding and enlargement within a hyphal segment. The other type of asexual spore is a sporangiospre, formed within a sporangium, or sac, at the end of an aerial hypha called a sporangiosphore. The sporangium can contain hundreds of sporangiospores.

What are some of the ways fungi differ from bacteria in terms of environmental requirements and nutritional characteristics?

-Fungi usually grow better in an environment with a pH of about 5, which is too acidic for the growth of most common bacteria. -Almost all molds are aerobic. Most yeasts are facultative anaerobes. -Most fungi are most resistant to osmotic pressure than bacteria; most can therefore grow in relatively high sugar or salt concentrations. -Fungi can grow on substances with a very low moisture content, generally too low to support the growth of bacteria. -Fungi require somewhat less nitrogen than bacteria for an equivalent amount of growth. -Fungi are often capable of metabolizing complex carbohydrates, such as lignin (a component of wood), that most bacteria cannot use for nutrients.

What are the similarities and differences between systemic, subcutaneous, and cutaneous mycoses?

-Systemic mycoses are fungal infections deep within the body. They are not restricted to any particular region of the body but can affect a number of tissues and organs. Systemic mycoses are usually cause by fungi that live in the soil. Inhalation of spores is the route of transmission; these infections typically being in the lungs and then spread to other body tissues. They are not contagious from animal to human or from human to human. Two systemic mycoses, histoplasmosis and coccidioidomycosis. -Subcutaneous mycoses are final infections beneath the skin cause by saprophytic fungi that live in soil and on vegetation. Sporotrichosis is a subcutaneous infection acquired by gardeners and farmers. Infection occurs by direct implantation of spores of mycelial fragments into a puncture wound in the skin. -Cutaneous mycoses fungi that infect only the epidermis, hair, and nails are called dermatophytes, and their infections are called dermatomycoese or cutaneous mycoses.Dermatophytes secrete keratinase, an enzyme that degrades keratin, a protein found in hair, skin, and nails. In- fection is transmitted from human to human or from animal to human by direct contact or by contact with infected hairs and epidermal cells (as from barber shop clippers or shower room f loors).

94. What four generalizations distinguish parasitic from free-living helminths?

1. They may lack a digestive system. They can absorb nu- trients from the host's food, body fluids, and tissues. 2. Their nervous system is reduced. They do not need an extensive nervous system because they do not have to search for food or respond much to their environment. The environment within a host is fairly constant. 3. Their means of locomotion is occasionally reduced or com pletely lacking. Because they are transferred from host to host, they do not need to search actively for a suitable habitat. 4. Their reproductive system is often complex. An individual produces large numbers of eggs, by which a suitable host is infected.

What happens in protozoan conjugation?

2 cells fuse, and a haploid nucleus (the micronucleus) from each cell migrates to the other cell. This haploid micronucleus fuses with the haploid micronucleus within the cell. The parent cells separate, each now a fertilized cell. When the cells later divide they produce daughter cells with recombined DNA

What is plasmogamy? Karyogamy? Meiosis?

A fungal sexual spre results from sexual reproduction, which consists of three phases: 1) Plasmogamy- A haploid nucleus of a donor cell (+) penetrates the cytoplasm of a recipient cell (-). 2) Karyogamy- The (+) and (-) nuclei fuse to form a diploid zygote nucleus. 3) Meiosis: The diploid nucleus gives rise to haploid nuclei (sexual spores), some of which may be genetic recombinants.

What disease is caused by giardia lamblia?

A parasite without mitochondria, the parasite is found in the small intestine of humans and other mammals, it is excreted in the feces as a cyst and survives in the environment before being ingested by the next host

What is pneumocytsis? What type of mycosis does it produce? What kind of pathogen is it?

A parasitic protozoan that can cause fatal pneumonia in people with immunodeficiency disease

What are conidia?

A unicellular of multicellular spore that is not enclosed in a sac. Conidia are produced in a chain at the end of conidiophore. Conidia formed by the fragmentation of a septate hypha into single, slightly thickened cells are called arthroconidia.

96. What does dioecious and hermaphroditic mean?

Adult helminths may be dioecious; male reproductive or- gans are in one individual, and female reproductive organs are in another. In those species, reproduction occurs only when two adults of the opposite sex are in the same host. Adult helminths may also be monoecious, or hermaphroditic— one animal has both male and female reproductive organs. Two hermaphrodites may copulate and simultaneously fertilize each other. A few types of hermaphrodites fertilize themselves.

107. What are hookworms and why are they important?

Adult hookworms, Necator americanus (ne-kāʹtôr ä-me-ri-kaʹnus) and Ancylostoma duodenale (an-sil-osʹtoma düʹo-den-al-ē), live in the small intestine of humans (Figure 25.23, page 741); the eggs are excreted in feces. The larvae hatch in the soil, where they feed on bacteria. A larva enters its host by penetrating the host's skin. It then enters a blood or lymph vessel, which carries it to the lungs. It is coughed up in sputum, swallowed, and finally carried to the small intestine.

Which categories are protozoans in terms of nutrition?

Aerobic heterotrophs

How do ascospores differ from conidia?

An ascospore results from the fusion of the nuclei of two cells that can be either morphologically similar or dissimilar.

What is an opportunistic pathogen?

An opportunistic pathogen generally harmless in its normal habitat but can become pathogenic in a host who is seriously debilitated or traumatized, who is is under treatment with broad-spectrum antibiotics, whose immune system is suppressed by drugs or by an immune disorder, or who has a lung disease.

What is Stachybotrys and why is it important?

Another example of an opportunistic pathogen is the fungus Stachybotrys , which normally grows on cellulose found in dead plants but in recent years has been found growing on water-damaged walls of homes.

What is coccidiodomycosis?

Another fungal pulmonary disease, rather restricted geographically, causative agent is coccidioides immitis, a dimorphic fungus

76. What does Plasmodium cause and why is that important?

Apicomplexans have a complex life cycle that involves trans- mission between several hosts. An example of an apicomplexan is Plasmodium (plaz-mōʹdē-um), the causative agent of malaria. Malaria affects 10% of the world's population, with 300 to 500 million new cases each year. The complex life cycle makes it dif- ficult to develop a vaccine against malaria.

What are apicomplexa? What are they important?

Are not motile in their mature forms and are obligate intercellular parasites, characterized by the presence of a complex of special organelles at the apexes (tips) of their cells

What are dinoflagellates and why are they medically important?

Are unicellular algae collectively called plankton or free floating organisms produce 80% of the earths O2

What are diatoms and why are they sometimes medically important?

Are unicellular or filamentous algae with complex cell walls that consist of pectin and a layer of silica. Store energy captured through photosynthesis in the form of oil

What are Protozoa?

Are unicellular, eukaryotic organisms, Protozoa inhabit water and soil

106. Why is Ascaris important? What is their life cycle?

Ascaris lumbricoides (asʹkar-is lum-bri-koiʹdēz) is a large nematode (30 cm in length) that infects over 1 billion people worldwide (Figure 25.24, page 742). It is dioecious with sexual dimorphism; that is, the male and female worms look dis- tinctly different, the male being smaller with a curled tail. The adult Ascaris lives in the small intestines of humans exclu- sively; it feeds primarily on semidigested food. Eggs, excreted with feces, can survive in the soil for long periods until acci- dentally ingested by another host. The eggs hatch in the small intestine of the host. The larvae then burrow out of the intes- tine and enter the blood. They are carried to the lungs, where they grow. The larvae will then be coughed up, swallowed, and returned to the small intestine, where they mature into adults.

What is the life cycle of Rhizopus? (sexual and asexual)

Asexual Reproduction: 1) Aerial hypha produces a sporangium 2) Sporangium bursts to release spores 3) Spore germinates to produce hyphae 4) Vegetative mycelium grows. Sexual reproduction: 1) Aerial hypha produces a sporangium 2) Sporangium bursts to release spores 3) Spore germinates to produce hyphae 4) Vegetative mycelium grows. 5) Gametes form at tip of hypha 6) Plasmogamy 7) Zygospore forms 8) Karyogamy and meiosis 9) Zygote produces a sporangium 10) Spores are released from sporangium 11) spore germinates to produce hyphae

What is the life cycle of Enephalitozoon, a microsporidian?

Asexual reproduction: 1) Spores are ingested or inhaled 2) Spore injects tube into host cell 3) Cytoplasm and nucleus enter 4) Cytoplasm grows, and nuclei reproduce 5) Cytoplasm breaks up around the nuclei to form spores. 6) New spores are released.

83. Name four other Apicomplexa that are human pathogens besides Plasmodium.

Babesia microti toxoplasma gondi cryptosporidium cyclospora

84. What diseases do they cause? (see pages 356, 668, 673, 737, 738 & 740)

Babesia microti: babesiosis, fever, anemia, affects rbc, ticks toxoplasma gondi: toxoplasmosis, in cats, feces cryptosporidium: diarrhea, inside cells of small intestine, to humans by feces of animals cyclospora: diarrhea, snowpeas in US

How are fungal spores similar and different from endospores?

Bacterial endospores allow a bacterial cell to survive adverse environmental conditions. A single vegetative bacterial cell forms one endospore, which eventually germinates to produce a single vegetative bacterial cell. This process is not reproduction because it does not increase the total number of bacterial cells. But after a mold forms a spore, the spore detaches from the parent and germinates into a new mold. Unlike the bacterial endospore, this is a true reproductive spore; a second organism grows from the spore. Although fungal spores can survive for extended periods in dry or hot environments, most do not exhibit the extreme tolerance and longevity of bacterial endospores.

What is the difference between budding and fission yeasts?

Budding yeasts, such as Saccharomyces, divide unevenly. In budding, the parent cell forms a protuberance (bud) on its outer surface. As the bud elongates, the parent cell's nucleus divides, and one nucleus migrates into the bud. Cell wall material is then laid down between the bud and parent cell, and the bud eventually breaks away. Fission yeasts, such as Schizosaccharomyces, divide evenly to produce two new cells. During fission, the parent cell elongates, its nucleus divides, and two offspring cells are produce. Increases in the number of yeast cells on a solid medium produce a colony similar to a bacterial colony.

Which pathogen is the most common of yeast infections?

Candida albicans

What is pneumocystis pneumoniae?

Caused by pneumocystis jirovecii, the toxonomic position of this microbe has been uncertain ever since its discovery in 1909 has characteristics of both a protozoan and fungus, analysis of RNA and certain other structural characteristics indicate that it is closely related to certain yeasts and it is usually reported a fungus

101. What are cestodes or tapeworms? Why are they medically important? (see pages 732-737 for information in this area & information to answer upcoming questions)

Cestodes, or tapeworms, are intestinal parasites

102. What are characteristics of tapeworms?

Cestodes, or tapeworms, are intestinal parasites. Their structure is shown in Figure 12.27. The head, or scolex (plural: scoleces), has suckers for attaching to the intestinal mucosa of the defini- tive host; some species also have small hooks for attachment. Tapeworms do not ingest the tissues of their hosts; in fact, they completely lack a digestive system. To obtain nutrients from the small intestine, they absorb food through their cuticle. The body consists of segments called proglottids. Proglottids are continu- ally produced by the neck region of the scolex, as long as the scolex is attached and alive. Each mature proglottid contains both male and female reproductive organs. The proglottids far- thest away from the scolex are the mature ones containing eggs. Mature proglottids are essentially bags of eggs, each of which is infective to the proper intermediate host.

89. What is Chagas' disease and why is it important? (see pages 356 and 666)

Chagas' disease, also known as American trypanosomiasis, is a protozoan disease of the cardiovascular system human pathogen: trypanosome cruzi source: bite of triatoma (kissing bug)

What is a cystostome used for?

Ciliates take in food by waving their cilia toward a mouth like opening called a cytosome

Which important human pathogens are dimorphic?

Coccidiomycosis,blastomycosis

What is arthroconidia? Blastoconidia? Chamydoconidia?

Condidia formed by the fragmentation of a septate hypha into single, slightly thickened cells are called arthroconidia. Another type of conidium, blastoconidia, consists of buds coming off the parent cell. (i.e. Candida albicans). A chlamydoconidium is a thick-walled spore formed by rounding and enlargement within a hyphal segment.

87. How are Cryptosporidium transmitted?

Cryptosporidium (krip-tō-spô-riʹdē-um) lives inside the cells lining the small intestine and can be transmitted to humans through the feces of cows, rodents, dogs, and cats

What is Candida albicans? What type of mycosis does it produce? What kind of pathogen is it? Where is it typically found?

Diploid fungus that grows both as yeasts and filamentous cells and a causal agents of opportunistic oral and genital infections in humans, most common human fungal pathogen normally harmless is those with not weakened immune systems

What is cryptococcus gattii? Why is it important?

Encapsulated yeast found primarily in tropical and subtropical climates

What is the trophozoite stage?

Feeding and growing stage, feeds upon bacteria small particulate nutrients

What do they eat?

Feeds upon bacteria, small particulate nutrients

What are the three ways that Protozoa can reproduce asexually?

Fission, budding, or schizogony

What is in them that is responsible for photosynthesis?

Found throughout the photic (light) zone of bodies of water, chlorophyll a ( a light trapping pigment) and accessory pigments involved in photosynthesis are responsible for the distinctive colors of many algae

What are chemoheterotrophs?

Fungi are chemoheterotrophs, and, like bacteria, they absorb nutrients rather than ingesting them like animals do.

Compare fungi to bacteria. Be able to state major differences between the two. (see table 12.1)

Fungi are eukaryotic, bacteria are prokaryotic. In the cell membrane of fungi sterols are present, in bacteria sterols are absent (except in Mycoplasma). In fungi cells walls have glucans; manna's; chitin, and in bacteria cell walls have peptidoglycan. In fungi spore are sexual and asexual reproductive spores, in bacteria endospores (not for reproduction); some asexual reproductive spores. In fungi metabolism is limited to heterotrophic; aerobic, facultatively anaerobic, in bacteria metabolism is heterotrophic, autotrophic, aerobic, facultatively anaerobic, anaerobic.

What are fungi important in medicine?

Fungi are used by humans to produce drugs such as alcohol and penicillin.

Why are spores important in the study of fungi?

Fungi are usually identified by spore type.

What forms of reproduction are used by fungi?

Fungi can reproduce asexually or sexually. Both sexual and asexual reproduction in fungi occurs by the formation of spores.

What is ringworm?

Fungi that colonize the hair, nails, and the outer layer (stra- tum corneum) of the epidermis (see Figure 21.1) are called dermatophytes; they grow on the keratin present in those loca- tions. Termed dermatomycoses, these fungal infections are more informally known as tineas or ringworm. Tinea capitis, or ring- worm of the scalp, is fairly common among elementary school children and can result in bald patches. This characteristic led the Romans to adopt the name tinea, Latin for clothes moth, because the infection resembles the holes left by the wormlike larvae of the moth in wool clothing. The infections tend to expand cir- cularly, hence the term ringworm (Figure 21.16a). The infection is usually transmitted by contact with fomites. Dogs and cats are also frequently infected with fungi that cause ringworm in children. Ringworm of the groin, or jock itch, is known as tinea cruris, and ringworm of the feet, or athlete's foot, is known as tinea pedis (Figure 21.16b). The moisture in such areas favors fungal infections.

What are some characteristics of this medically important phyla?

Have a complex life cycle that involves transmission between several hosts making it hard to develop a vaccine

81. Why might malaria increase in the United States? (see pages 668-672)

In recent years, however, there has been an upward trend in the number of U.S. cases, reflecting a world- wide resurgence of malaria, increased travel to malarial areas, and an increase in immigration from malarial areas. Occasion- ally, malaria has been transmitted by unsterilized syringes used by drug addicts. Blood transfusions from people who have been in an endemic area are also a potential risk.

What is cryptococcus neoformans? What type of mycosis does it produce? What kind of pathogen is it? Where is it typically found?

Is an encapsulated yeast that can live in both plants and animals, it's teleomorph is filobasidiella neoformans, a filamentous fungus belonging to the class tremellomycetes, often found in bird excrement

What is schizogony?

Is multiple fission; the nucleus undergoes multiple divisions before cell divides, after many nuclei are formed a small portion of cytoplasm concentrates around each nucleus, then the single cells separated into daughter cells

What disease does entamoeba histolytica cause? How is it transmitted?

Is the only pathogenic ameba found in the human intestine

What is aspergillosis?

It is airborne by the conidia of aspergillus fumigatus and other species of aspergillus which are widespread in decaying vegetation . Compost piles are ideal sites for growth and farmers and gardeners are most often exposed to infective amounts

What are hyphae?

Long filaments of cells joined together. Hyphae can grow to immense proportions.

104. Why are nematode or roundworms medically important?

Members of the Phylum Nematoda, the roundworms, are cy- lindrical and tapered at each end. Roundworms have a complete digestive system, consisting of a mouth, an intestine, and an anus. Most species are dioecious. Males are smaller than females and have one or two hardened spicules on their posterior ends. Spicules are used to guide sperm to the female's genital pore.

What are Microsporidia and why are they important?

Microsporidia are unusual eukaryotes because they lack mitochondria. Microsporidia do not have microtubules, and they are obligate intracellular parasites.In 1857, when they were discovered, microsporidians were classified as fungi. They were reclassified as protists in 1983 be- cause they lack mithochondria. Recent genome sequencing, however, reveals that the microsporidians are fungi. Sexual re- production has not been observed but probably occurs within the host (Figure 12.8). Microsporidia have been reported since 1984 to be the cause of a number of human diseases, including chronic diarrhea and keratoconjunctivitis (inflammation of the conjunctiva near the cornea), most notably in AIDS patients.

What are some of the characteristics of mold?

Mold has a body call the thallus, has long filaments of cells joined together called hyphae, in most molds the hyphae contain cross-walls called septa.

What is the study of fungi called?

Mycology

What is Rhizopus? What type of mycosis does it produce? What kind of pathogen is it? What kind of spores does it produce?

Mycosis it produces: Mucormycosis. mucormycosis is an opportunistic mycosis caused by rhizopus the infection occurs mostly in patients who have diabetes, luekima, or are undergoing treatment with immunosuppressive drugs.

What causes primary amebic meningoencephalitis? And why is it important?

Naegleria fowleri- brain eating ameba Found in warm freshwater lakes rivers and hot springs and soil

Do many cause human disease?

No because Protozoa are specific for grasshoppers

92. Know the definition of obligate intracellular parasite.

Obligate intracellular parasites cannot reproduce outside their host cell, meaning that the parasite's reproduction is entirely reliant on intracellular resources. Certain bacteria, including: Chlamydia, and closely related species. Rickettsia

108. What are whipworms and why are they important?

One billion people worldwide are infected with Trichuris trichiura, or whipworm. The worms are spread from person to person by fecal-oral transmission or through feces-contaminated food. The disease occurs most often in areas with tropical weather and poor sanitation practices and among children.

What is coccidioides immitis? What type of mycosis does it produce? What kind of pathogen is it?

Pathogenic fungus that resides in the soil in certain parts of the southwestern United States, causes valley fever, San Joaquin valley fever, desert bumps, posadas disease

78. What is a sporozoite?

Plasmodium grows by sexual reproduction in the Anopheles (an-ofʹel-ēz) mosquito (Figure 12.20). When an Anopheles car- rying the infective stage of Plasmodium, called a sporozoite, bites a human, sporozoites can be injected into the human. The sporozoites undergo schizogony in liver cells and produce thousands of progeny called merozoites, which infect red blood cells.

What is Pneumocystis and why is it important?

Pneumocystis is an opportunistic pathogen in individuals with compromised immune systems and is the most common life-threatening infection in AIDS patients. It was first classified as a protozoan, but recent studies of its RNA indicate it is a unicellular anamorphic fungus

What are pseudopods and what is phagocytosis?

Pseudopods-Amebae move by extending blunt, lobelike projections if the cytoplasm Phagocytosis-

What is the difference between septated and coenocytic hyphae?

Septate hyphae- these hyphae contain cross-walls called septa, which divide them into distinct, uninucleate (one-nucleus) cell-like units. Coenocytic hyphae-the hyphae contain no septa and appear as long, continuous cells with many nuclei. **Even in fungi with septate hyphae, there are usually openings in the septa that make the cytoplasm of adjacent "cells" continuous; these fungi are actually coenocytic organisms, too.

What are the characteristics of algae?

Simple eukaryotic photoautotrophs that lack the tissues (roots,stem, and leaves) of plants, most algae are found in the ocean, their locations depend on the availability of appropriate nutrients, wavelengths of light, and surfaces in which to grow,

What is final dimorphism? under what circumstances would you expect to find fungal dimorphism?

Some fungi, most notably the pathogenic species, exhibit dimorphism-- two forms of growth. Such fungi can grow either as a mold or as a yeast. The mold like forms produce vegetative and aerial hyphae; the yeastlike forms reproduce by budding. Dimorphism in pathogenic fungi is temperature-dependent: at 37 degrees Celsius, the fungus is yeastlike and at 25 degrees Celsius, it is mold like. However, the appearance of the dimorphic (in this instance, nonpathogenic) fungus changes with CO2 concentration.

What are pseudohyphae? How do they differ from hyphae?

Some yeasts produce buds that fail to detach themselves; these buds form a short chain of cells called a pseudohypha. • Hyphae may or may not contain septa, whereas pseudonymous always contain septa. • There is no constriction at the place where septa found in hyphae, whereas it is found in pseudohyphae. • Hyphae can be coenocytic (single celled, multinuclear) or multicellular, but pseudohyphae are always multicellular. • Hyphae do not show budding whereas pseudohyphae do show budding through which it grows continuously. • Hyphae are always stationary, whereas pseudohyphae are used to invade cells by growing faster by budding by showing some kind of mobility.

Why can pulmonary infections due to Rhizopus, Aspergillus, & Mucor be so dangerous?

Such diseases can be very dangerous, par- ticularly invasive infections of pulmonary aspergillosis. Predis- posing factors include an impaired immune system, cancer, and diabetes. As with most systemic fungal infections, there is only a limited arsenal of antifungal agents available; amphotericin B has proved the most useful.

What is histoplasmosis?

Superficially resembles turberculosis, first recognized as a wide spread disease in the United States when x-Ray surveys showed lung lesions in many people who were turberculin test negative, lungs are most likely to be initially infected, the pathogens may spread in the blood and lymph causing lesions in almost all organs of the body

103. What is the life cycle of the beef tapeworm? the pork tapeworm?

The adults of Taenia sagi nata (teʹnē-ä sa-ji-näʹtä), the beef tapeworm, live in humans and can reach a length of 6 m. The scolex is about 2 mm long and is followed by a thousand or more proglottids. The feces of an infected human contain mature proglottids, each of which contains thousands of eggs. As the proglottids wriggle away from the fecal material, they increase their chances of being ingested by an animal that is grazing. Upon ingestion by cattle, the larvae hatch from the eggs and bore through the intestinal wall. The larvae migrate to muscle (meat), in which they encyst as cysticerci. When the cysticerci are in- gested by humans, all but the scolex is digested. The scolex anchors itself in the small intestine and begins producing proglottids. Diagnosis of tapeworm infection in humans is based on the presence of mature proglottids and eggs in feces. Cysticerci can be seen macroscopically in meat; their presence is referred to as "measly beef." Inspecting beef that is intended for human con- sumption for "measly" appearance is one way to prevent infections by beef tapeworm. Another method of prevention is to avoid the use of untreated human sewage as fertilizer in grazing pastures. Humans are the only known definitive host of the pork tape- worm, Taenia solium. Adult worms living in the human intestine produce eggs, which are passed out in feces. When eggs are eaten by pigs, the larval helminth encysts in the pig's muscles; humans become infected when they eat undercooked pork. The human- pig-human cycle of T. solium is common in Latin America, Asia, andAfrica.IntheUnitedStates,however,T.soliumisvirtually nonexistent in pigs; the parasite is transmitted from human to human. Eggs shed by one person and ingested by another person hatch, and the larvae encyst in the brain and other parts of the body, causing cysticercosis (see Figure 25.21, page 739). The human hosting T.solium's larvae is serving as an intermediate host. Approximately 7% of the few hundred cases reported in recent years were acquired by people who had never been out- side the United States. They may have become infected through household contact with people who were born in or had traveled in other countries.

What is a thallus?

The body of a mold or fleshy fungus.

99. What is the life cycle of the blood fluke Schistosoma? (see pages 666-667)

The cercariae of the blood fluke Schistosoma (shis-tō-sōʹma) are not ingested. Instead, they burrow through the skin of the human host and enter the circulatory system. The adults are found in certain abdominal and pelvic veins. The disease schistosomiasis is a major world health problem

91. What are hemoflagellates?

The hemoflagellates (blood parasites) are transmitted by the bites of blood-feeding insects and are found in the circula- tory system of the bitten host. To survive in this viscous fluid, hemoflagellates usually have long, slender bodies and an undu- lating membrane. The genus Trypanosoma (tri-paʹnō-sō-mä) includes the species that causes African sleeping sickness, T. brucei (brüsʹē), which is transmitted by the tsetse fly. T. cruzi (kruzʹē; see Figure 23.23, page 667), the causative agent of Chagas' disease, is transmitted by the "kissing bug," so named because it bites on the face (see Figure 12.33d on page 363). After entering the insect, the trypanosome rapidly multi- plies by schizogony. If the insect then defecates while biting a human, it can release trypanosomes that can contaminate the bite wound.

What are some defining characteristics of the life cycle of parasitic helminths?

The life cycle of parasitic helminths can be extremely complex, involving a succession of intermediate hosts for completion of each larval (developmental) stage of the parasite and a definitive host for the adult parasite. Adult helminths may be dioecious; male reproductive or- gans are in one individual, and female reproductive organs are in another. In those species, reproduction occurs only when two adults of the opposite sex are in the same host. Adult helminths may also be monoecious, or hermaphroditic— one animal has both male and female reproductive organs. Two hermaphrodites may copulate and simultaneously fertilize each other. A few types of hermaphrodites fertilize themselves.

79. What is an intermediate host and what is a definitive host?

The mosquito is the definitive host because it harbors the sexually reproducing stage of Plasmodium. The host in which the parasite undergoes asexual reproduction (in this case, the human) is the intermediate host.

82. Compare Plasmodium vivax to Plasmodium falciparum. Why is the latter so much more dangerous? (see page 670)

The most dangerous malaria is that caused by P. falciparum. Perhaps one reason for the virulence of this type of malaria is that humans and the parasite have had less time to become adapted to each other. It is believed that humans have been exposed to this parasite (through contact with birds) only in relatively recent history. Referred to as "malignant" malaria, untreated it eventu- ally kills about half of those infected. The highest mortality rates occur in young children. More red blood cells (RBCs) are infected and destroyed than in other forms of malaria. The resulting ane- mia severely weakens the victim. Furthermore, the RBCs develop surface knobs that cause them to stick to the walls of the capil- lary vessels, which become clogged. This clogging prevents the infected RBCs from reaching the spleen, where phagocytic cells would eliminate them. The blocked capillaries and subsequent loss of blood supply leads to death of the tissues. Kidney and liver damage is caused in this fashion. The brain is frequently affected, and P. falciparum is the usual cause of cerebral malaria.

105. What is the life cycle of pinworms? How are they detected?

The pinworm Enterobius vermicularis (en-te-rōʹbē-us ver-mi-kū-larʹis) spends its entire life in a human host (Fig- ure 12.29). Adult pinworms are found in the large intestine. From there, the female pinworm migrates to the anus to de- posit her eggs on the perianal skin. The eggs can be ingested by the host or by another person exposed through contami- nated clothing or bedding.

What are sporangiospores?

They are formed within a sporangium, or sac, at the end of an aerial hypha called a sporangiophore. The sporangium can contain hundreds of sporangiospores. Such spores are produced by Rhizopus.

What is Aspergillus? What type of mycosis does it produce? What kind of pathogen is it? What kind of spores does it produce?

This disease occurs in people who have debilitating lung disease or dance and have inhaled Apergillus spores.

98. What is the life cycle of the lung fluke?

To exemplify a fluke's life cycle, let's look at the lung fluke, Paragonimus, spp (pãr-ä-gōnʹe-mus). Paragonimus species oc- cur throughout the world. P. kellicotti (kel ́li-kot-tē), endemic in the United States, has been associated with eating rawcrayfish on river raft trips. The adult lung fluke lives in the bronchioles of humans and other mammals and is approxi- mately 6 mm wide and 12 mm long. The hermaphroditic adults liberate eggs into the bronchi. Because sputum that contains eggs is frequently swallowed, the eggs are usually excreted in feces of the definitive host. If the life cycle is to continue, the eggs must reach a body of water. A series of steps occurs that ensure adult flukes can mature in the lungs of a new host

86. What is the life cycle of Toxoplasma gondii?

Toxoplasma gondii (toks-ō-plazʹmä gonʹdē-ē) is another api- complexan intracellular parasite of humans. The life cycle of this parasite involves domestic cats. The trophozoites, called tachyzoites, reproduce sexually and asexually in an infected cat, and oocysts, each containing eight sporozoites, are excreted with feces. If the oocysts are ingested by humans or other animals, the sporozoites emerge as trophozoites, which can reproduce in the tissues of the new host (see Figure 23.24, page 669). T. gondii is dangerous to pregnant women because it can cause congenital in- fections in utero. Tissue examination and observation of T. gondii are used for diagnosis. Antibodies may be detected by ELISA and by indirect fluorescent-antibody tests (see Chapter 18).

97. What are trematodes or flukes?

Trematodes, or flukes, often have flat, leaf-shaped bodies with a ven- tral sucker and an oral sucker (Figure 12.25). The suckers hold the organism in place. Flukes obtain food by absorbing it through their nonliving outer covering, called the cuticle. Flukes are given common names according to the tissue of the definitive host in which the adults live

109. What is trichinellosis and why is it important?

Trichinellosis is caused by a nematode that the host ac- quires by eating encysted larvae in undercooked meat of infected animals (see page 743). The nematode, Dirofilaria immitis (dirʹō-fi-lãr-ē-ä imʹmi-tis), is spread from host to hostthrough the bites of Aedes mosquitoes. It primarily affects dogs and cats, but it can infest human skin, conjunctiva, or lungs. Larvae injected by the mosquito migrate to various organs, where they mature into adults. The parasitic worm is called a heartworm because the adult stage is often in the animal host's heart, where it can kill its host through conges- tive heart failure (Figure 12.30). The disease occurs on every continent except Antarctica. Wolbachia bacteria appear to be essential to development of the worm embryos (see the box in Chapter 11 on page 308.)

What is encystment and why does it occur?

Under certain adverse conditions, some Protozoa produce a protective capsule called a cyst, a cyst permits the organism to survive when food,moisture, or oxygen are lacking, when temps are not suitable, or when toxic chemicals are present

What is blastomycosis?

Usually called North American blastomycosis, caused by the fungus blastomyces dermatitidis, a dimorphic fungus found most often in the Mississippi and Ohio river valleys where it grows in soil, infections are a symptomatic, infection begins in the lungs and resembles bacterial pneumonia and can spread rapidly

What is a mycelium?

When environmental conditions are suitable, the hyphae grow to form a filament mass, which is visible to the unaided eye.

What is a yeast?

Yeasts are non filamentous, unicellular fungi that are typically spherical or oval. Like molds, yeasts are widely distributed in nature; they are frequently found as a white powdery coating on fruits and leaves.

88. What is Leishmaniasis and why is it important? (see pages 356 and 672)

a disease its human pathogen is leishmania the source is a bite of a sand fly. contact with contaminated blood from transfusions or shared needles can also lead to infection.

85. Which one is associated with ticks & has been found in Minnesota & Wisconsin?

babesia microti

What is Histoplasma capsulatum? What type of mycosis does it produce? What kind of pathogen is it? What kind of spores does it produce?

conidia spore type. habitat soil, systemic type of mycosis.

What does Domoic acid cause?

diatoms produce A toxin that then concentrated in the mussels, symptoms include diarrhea, and memory loss

What are ciguatera?

diseaseOccurs when the dinoflagellate gambierdiscus toxicus passes up the food chain and is concentrated in large fish. endemic, constantly present

77. What is the life cycle of Plasmodium vivax?

figure 12.20

90. What is African trypanosomiasis and why is it important? (see pages 354 & 629)

human pathogen: t. brucei gambiense. t.b. rhodesiense source:bite of tsetse fly African trypanosomiasis, or sleeping sickness, is a protozoan dis- ease that affects the nervous system.

80. What are the intermediate and definitive hosts for malaria?

intermediate: human definitive: mosquito

93. What are the two major categories of parasitic helminths?

platyhelminthes (flatworms) and Nematoda (roundworms)

100. Why is schistosomiasis important?

world problem