Microbiology Exam #2 Ch. 12
What is a vector? Name 2 protozoan and 2 helminth diseases requiring vectors.
A vector: an organism that transmits a disease. Two protozoans that have vectors: Euglena-African Sleeping Sickness and Plasmodium-Malaria. Two helminths: Trichinella-causes inflammation in eyes, nails, digestive tract from pork with encysted larval worms. Cestodes which are tapeworms that infect GI from undercooked meats.
Know the differences between the following asexual spore types found in fungi: arthrospores, chlamydospores, sporangiospores, conidiospores, blastospores.
(1). Arthrospores are thickened fragments of septate hyphae (2). Chlamydospores are rounded swollen section of septate hyphae (3). Sporangiospores are spores encased in a protective sack (4). Conidiospores are chains of spores with NO protective sack (5). Blastospores are multiple buds off of parent cells
Be able to describe the types of sexual and asexual reproduction which occur in protozoans.
-Asxeual reproduction happens through mitosis as the offspring has two identical parents. Processes like fission, budding and schizogony is how they get by. Fission is when the cytoplasm splits into equal halves, budding is when the smaller daughter cells are produced and attached to the outside of the mother cell, and lastly, schizogony is when multiple nuclear divisions without cytoplasmic divisions and creates multinuclear cells. -Sexual reproduction requires meiosis that allows for genetic variability, recombination, and change. Processes like conjugation and gametocytes help with this. Conjugation is the insertion of a haploid micronucleus into another cell that leads to fusion to form a diploid zygote then ultimately cytokinesis. As for gametocytes (gamete cells), haploid cells fuse with the opposite mating type to form zygotes.
Know the functions of the following structures found in Protozoans: cytosome/ oral groove, storage vacuoles, anal pores, macronucleus, micronucleus, cyst, trophozoite.
-Cytosome (=oral groove) is the mouth to bring nutrients into the cell. -Food vacuoles are for storage and digestion like a stomach. -The Anal pore is for excretion of wastes and the contractile vacuole is used to squirt out excess fluids to maintain osmotic balance. -A trophozoite is a motile, metabolically active cell with a soft pellicle (no rigid cell wall) -whereas a cyst is a thick-walled, dormant, protected cell that is designed for survival outside of the host. The trophozoite and cyst are both stages of protozoa cells that are cycled throughout their life, depending on their environmental conditions. The troph stage is known to eat human intestinal tissues and RBCs and the Cyst stage can survive in dirty water sources for weeks and still be infectious to other humans. When conditions are harsh cysts are formed, when life is good trophs take advantage of the nutrient-rich environment. The macronucleus is the centre of all metabolic activities of the organism. The micronucleus is a storage site for the germline genetic material of the organism
Know the differences between the following sexual spore types found in fungi: zygospores, ascospores, basidiospores.
-Zygospores are spores encased in a thick, spiny structure formed around a diploid zygote -Ascospores are found in a sack or pod-like structure called an ascus. -Basidiospores are found under the fruiting structures (cap) of mushrooms.
For the Nematodes, list their general characteristics and the pathogenic examples given in lecture. For the pathogens, know the disease caused and transmission mode.
1) Enterobius(pinworm)- Common in US preschool aged kids (10%) and their families. Oral/fecal transmission. Primary symptoms- perianal itching. Scotch tape ID. 2)Ascaris- ⅓ humans infected world-wide. Mostly asymptomatic. May migrate out anus, nose, umbilicus. 10 inch adults. Eggs in feces. Transmitted by oral/fecal route (dirty water) 3)Necator- Hookworms (2nd most common in humans) 20% humans worldwide Chronic, causes severe anemia. Transmitted by larval in soil enter skin of bare feet 4)Trichinella-1% humans. Mild disease. Causes inflammation of eyes, nails, digestive tract. Transmitted by improperly cooked pork with encysted larval worms
What are buds? How are fungal spores different from bacterial spores? What is a dimorphic fungus?
Buds are small outgrowths from the parent organism, which eventually become a new individual and they are asexually produced by mitosis. Mother cells of yeast can produce 24 daughter cells that each leave behind a bud scar on their surface. Fungal spores are different from bacterial spores because these spores are used for reproduction whereas bacteria use them for protection. Dimorphic fungi are fungi that can exist in the form of both mold and yeast. An example is Penicillium marneffei, a human pathogen that grows as a mold at room temperature, and as a yeast at human body temperature.
Know how fungi are classified. Know the characteristics and examples given for the following Phyla of fungi: Zygomycota, Ascomycota, Basidiomycota, Deuteromycota (Anamorphs)
Fungi are classified by their sexual spore type. The 4 phyla include: Zygomycota, Ascomycota, Basidiomycota, and Deuteromycota (anamorphs). The Zygomycota are the conjugation fungi and are Saprophytic otherwise known as being able to live off of decaying matter. Some examples include Rhizopus, also known as ordinary bread mold. Another would be Mucor and its ability to be an opportunistic infection causing respiratory and systemic mycosis. The Ascomycota are sac fungi (like ascus that protects sexual spores) that are often dimorphic. Some examples include Aspergillus and Histoplasma that cause pneumonia and Trichophyton that causes athlete's foot. These examples are common environmental species which cause infections ranging from life threatening to simply annoying. The next one is Basidiomycota otherwise known as "club fungi" because of their club shaped basidiospores. An example would be Cryptococcus that causes pneumonia. Lastly, Anamorphs also known as "fungi imperfecti" because they only reproduce asexually. They are also related to Ascomycota by RNA genes. Some examples include Candida which form vaginita and thrush, Coccidiodes which form Valley Fever that grows in the San Joaquin Valley, and Pneumocystis which forms a fatal structure of pneumonia in immunocompromised patients. The last example is a hallmark opportunistic infection that can lead to an AIDS diagnosis in HIV infected patients! All of these examples can be fatal if not properly taken care of.
Know the vegetative (non-reproductive) structures found in yeasts and molds: hyphae, mycelium, pseudohyphae.
Molds are multicellular with microscopic cell chains called hyphae. If these chains are separated they are called septate hyphae, but if the cytoplasm is shared then they are coenocytic. The macroscopic mass of hyphae is mycelium which can be seen with the naked eye, hence the term macro. Yeasts are single-celled organisms with short chains of unseparated cells called pseudohyphae ("false" hyphae).
How are protozoans classified today? How did they used to be classified? Know the characteristics and examples given for the following phyla of protozoans: Archezoa (Diplomonads/Parabasalids), Amebae, Apicomplexa, Ciliates, Euglenozoa. Know the diseases and transmission modes for the pathogens.
Protozoans used to be classified by motility but today they are classified by rRNA and are separated into 5 groups of phyla. The first is the Amoebozoa move by their pseudopodia ("false feet"). For example, Entamoeba histolytica causes amoebic dysentery in 10% of all humans infected by oral/fecal route. This organism eats the host's tissues and red blood cells and the patients become severely anemic and dehydrated. The second Archaezoa move using flagella and are considered evolutionary ancient because they lack mitochondria. Examples include Trichomonas vaginalis which causes vaginitis and urethritis and Giardia lamblia causes diarrheal syndrome. Ciliates are motile by cilia, most are free-living and only have one pathogen that is non-parasitic. An example is the Balantidium coli which causes severe/rare dysentery in the colon. The next one is Euglenozoa that have flagella and do have mitochondria. Some examples are the Euglena, which is not pathogenic but it is photosynthetic and Trypanosoma (Hemoflagellate) which causes African Sleeping sickness and chagas disease. Each species has different symptoms/disease, vectors and geography. Lastly, the Apicomplexa is NOT motile, obligate intracellular parasites that have very complex life cycles. An example would be Plasmodium that is a causal agent for malaria and it infects 300X10^6 humans. It also killed nearly one million every year and the life cycle is very complex with mosquitos being the vector of the disease.
For the Platyhelminthes, list their general characteristics, classes, pathogenic examples given in lecture. What is the difference between intermediate and definitive hosts? Be able to give two examples of intermediate hosts from the textbook. Know the diseases and transmission modes for the human pathogens.
The characteristics of the platyhelminthes (flatworms) are the trematodes and cestodes: Trematodes: -Flukes after the oval/leaf-shaped -One stage in life cycle -Suckers for attachment to host -Usually require an intermediate hosts -Hermaphroditic -Incomplete digestive system -Their definitive hosts are typically vertebrates including humans, birds, and fish EX: Schistosoma (liver or bladder fluke): Humans (250X10^6) are infected when larval forms (cercariae). Swims from water into skin. Intermediate hosts are small who become infected in water with human feces with eggs. The adult worm has a split body (schisto/soma). Usually in areas of poverty and poor sanitation. These worms are common parts of the world where waste material contaminates fresh water sources containing particular types of snails. Cestodes: -Tapeworms contracted from undercooked meats that infect GI -Grows meters long -Rarely serious -Scolex (head) has suckers and hooks to attach to host. (POA) -Segments (proglottids) hermaphroditic -Most mature point is the gravid, the proglottids farthest from the head that is full of fertilized egg. -One species produces cysts in human tissues (MT/NT). EX: Taenia sp. T. saginata: in beef, usually asymptomatic or mild T. solium: in pork, much worse, cysts can develop in human brain Definitive hosts are hosts that support adult worms whereas intermediate hosts contain larval or immature worms. Two intermediate hosts examples would be humans and a deer in the case of asexual reproduction of the tapeworm. Transmission modes that pathogens usually take are fecal/oral or through the skin.
