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Three Domain System Carl R. Woese Based on Ribosomes Ribosomes are in all cells but they are not all alike. Three Domains: 1. Eukaryotes 2. Bacteria- Prokaryotes (pathogenic bacteria and bacteria that live in soil and water) 3. Archaea- Prokaryotes (bacteria without peptidoglycan; methanogens, halophiles, and Figure 10.1 The Three-Domain System. Eukarya Fungi Origin of mitochondria Bacteria Origin of chloroplasts Animals Amebae Mitochondria Slime molds Cyanobacteria Proteobacteria Chloroplasts Archaea Methanogens Plants Extreme halophiles Ciliates Green algae Dinoflagellates Diatoms Hyperthermophiles Gram-positive bacteria Euglenozoa Thermotoga Horizontal gene transfer occurred within the community of early cells. Giardia Mitochondrion degenerates Nucleoplasm grows larger Taxonomic Hierarchy Domain Kingdom Phylum Class Order Family Genus Species Figure 10.5 The taxonomic hierarchy. All organisms Eukarya Archaea Bacteria Fungi None assigned for archaea None assigned for bacteria Ascomycota Euryarcheota Proteobacteria Hemiascomycetes Methanococci Gammaproteobacteria Saccharomycetales Methanococcales Enterobacteriales Saccharomycetaceae Methanococcaceae Enterobacteriaceae Domain Kingdom Phylum Class Order Family Genus Species Saccharomyces S. cerevisiae Baker’s yeast Methanothermococcus M. okinawensis Methanococcus Escherichia E. coli E. coli FUNGI Fungi Kingdom Fungi Nutritional Type Chemoheterotroph Multicellularity All, except yeasts Cellular Arrangement Unicellular, filamentous, fleshy Food Acquisition Method Absorptive Characteristic Features Sexual and asexual spores Mycology: the study of fungi Table 12.1 Selected Features of Fungi and Bacteria Compared. Vegetative Growth Molds ◦ The fungal thallus consists of hyphae; a mass of hyphae is a mycelium Unicellular fungi ◦ Fission yeasts divide symmetrically ◦ Budding yeasts divide asymmetrically Dimorphism ◦ Pathogenic dimorphic fungi are yeastlike at 37°C and moldlike at 25°C Figure 12.2 Characteristics of fungal hyphae. Cell wall Pore Nuclei Spore Septum Septate hypha Coenocytic hypha Growth of a hypha from a spore Figure 12.3a Aerial and vegetative hyphae. Aerial hyphae Aspergillus niger Figure 12.4 A budding yeast. Bud Parent cell Bud scar Figure 12.5 Fungal dimorphism. Yeastlike growth Moldlike growth Life Cycle Spores- reproductive fungal product ◦ Asexual- formed by one organism; genetically identical to parent ◦ Sexual- formed by the fusion of 2 nuclei from 2 organisms; genetic characteristics of both parents ◦ Most are asexual. Conidiospore Sporangiospore Unicellular or multicellular Spores are not enclosed in a sac. Spores are released one at a time. Has a sporangium(sac) that encloses the spores. More than one spore is released at one time. ASEXUAL SPORES Figure 12.6a Representative asexual spores. Conidia Conidiophore Figure 12.6e Representative asexual spores. Sporangiospores Sporangiophore Sexual Spores Zygospore: fusion of haploid cells produces one zygospore Ascospore: formed in a sac (ascus) Basidiospore: formed externally on a pedestal (basidium) Nutritional Adaptations pH-5 Aerobes(molds) and facultative anaerobes(yeast) Can grow in high salt and sugar environment and low moisture environments. Grow on a WIDE variety of substances. Fungal Diseases (Mycoses) Systemic mycoses: deep within body Subcutaneous mycoses: beneath the skin Cutaneous mycoses: affect hair, skin, and nails Superficial mycoses: localized, e.g., hair shafts Opportunistic mycoses: caused by normal microbiota or environmental fungi MEDICALLY IMPORTANT FUNGI Aspergillus sp. Opportunistic Found in decaying vegetation Usually affects immunocompromised or people with other lung infections Causes pulmonary aspergilliosis; cough, wheezing, fever Microsporum Cutaneous/Superficial Ringworm Circular patches are affected Transmitted with fomite contact Stachybotrys Opportunistic Found in water damaged walls of buildings Can lead to pulmonary problems Candida albicans Subcutaneous Normal flora of the genitourinary tract and mouth Dimorphic Overgrows when other normal flora is suppressed by antibiotics. Thrush and vaginitis(yeast infection) Figure 21.17 Candidiasis. Chlamydoconidia Pseudohyphae Blastoconidia Candida albicans Oral candidiasis, or thrush Pneumocystis jirovecii Systemic Causes pneumonia in people who are immunocompromised especially AIDS and cancer patients. Figure 24.20 The life cycle of Pneumocystis jirovecii, the cause of Pneumocystis pneumonia. Mature cyst Cyst Intracystic bodies Each trophozoite develops into a mature cyst. The mature cyst contains 8 intracystic bodies. The cyst ruptures, releasing the bodies. Trophozoite The trophozoites divide. The bodies develop into trophozoites. Trophozoite, note extensions for feeding on tissue. Economic Effects of Fungi Saccharomyces cerevisiae: bread, wine, HBV vaccine Can control pests. ALGAE Algae Kingdom Protista Nutritional Type Photoautotroph Multicellularity Some Cellular Arrangement Unicellular, colonial, filamentous, tissues Food Acquisition Method Diffusion Characteristic Features Pigments Figure 12.12a Algae and their habitats. Sublittoral zone SURFACE Unicellular green algae, diatoms, dinoflagellates Green algae, Littoral cyanobacteria, zone euglenoids LAND Red 𝛌 Multicellular green algae Orange 𝛌 Brown algae Yellow 𝛌 Violet 𝛌 Blue 𝛌 Algal habitats Red algae Life Cycle Sexual and Asexual- fragments can become a new algae Rhodophyta Red algae Cellulose cell walls Most are multicellular Store glucose polymer Harvested for agar(media plates) Dinoflagellates- Plankton Cellulose in plasma membrane Unicellular Store starch Neurotoxins cause paralytic shellfish poisoning Protozoans Protozoa Kingdom Various Nutritional Type Chemoheterotroph Multicellularity None Cellular Arrangement Unicellular Food Acquisition Method Absorptive; ingestive Characteristic Features Motility; some form cysts Characteristics of Protozoa Two Morphological forms: ◦ Trophozoites- vegetative form; oval to irregular shape ◦ Cysts-some produce; resistant form; round shape Characteristics of Protozoa Means of Motility ◦ Flagella ◦ Cilia ◦ Pseudopods Giardia lamblia No mitochondria Multiple flagella Adheres to the intestinal wall. Causes diarrhea Figure 25.17 The trophozoite form of Giardia lamblia, the flagellated protozoan that causes giardiasis. Insert Fig 25.17 Mark left by ventral sucker Trichomonas vaginalis No mitochondria Multiple flagella No cyst Vagina and male urinary tract STD- greenish yellow discharge Trypansoma brucei Hemoflagellate- lives in the bloodstream Tsetse fly African Sleeping Sickness- causes headache and fever that progress to coma Plasmodium sp. Nonmotile Intracellular parasites Complex life cycles Female Anopheles mosquito Blood and liver are affected Merozoites-infect RBCs, reproduce and the RBC ruptures 48 hours later Chills, fever, headache and vomiting. Alternating periods. Estimated 200-400 million people are in infected Figure 23.26 Malaria. RBCs Merozoites RBCs Merozoites being released from lysed RBCs Ring forms Malarial blood smear; note the ring forms. Entamoeba histolytica Pseudopods Causes cell lysis of the intestinal tissue which leads to bloody and mucoid diarrhea. Transmitted through feces. Figure 25.19 Section of intestinal wall showing a typical flask-shaped ulcer caused by Entamoeba histolytica. Normal mucosa Ulcer Insert Fig 25.19 Toxoplasmosis gondii Nonmotile Carried in a cat’s gut Transmission: ◦ Ingesting undercooked meat ◦ Contact with cat feces People with healthy immune systems may have mild cold-like symptoms or none at all Congenital infection ◦ Stillbirth ◦ Neurological damage Figure 23.24 The life cycle of Toxoplasma gondii, the cause of toxoplasmosis. 5 1 Cat ingests bradyzoites in tissue cysts of animals, usually mice. Immature oocyst is shed in cat feces. Immature cyst Definitive host 4 Sporozoites from ingested oocysts invade animal tissue and develop into bradyzoites within tissue cysts or into tissue-invading tachyzoites. Sporogony Bradyzoites Tachyzoites in tissue cyst Sporocysts If humans eat undercooked meat containing tissue cysts, they may become infected. Sporozoite 2 Intermediate hosts 3 If a pregnant woman accidentally ingests oocysts (contacted when changing a cat litter box), prenatal infection of the fetus may occur. Mature oocyst (10–13 μm x 9–11 μm) Mature oocysts develop by sporogony and contain two sporocysts, each with four infective sporozoites. Oocysts can infect many hosts, including mice, domestic animals, and humans, via ingestion. Balatidium coli Cilia Trophozoites secrete proteases that destroy cells of the large intestine. Causes severe dysentery. Transmitted through fecal contamination of water Helminths Helminths Kingdom Animalia Nutritional Type Chemoheterotroph Multicellularity All Cellular Arrangement Tissues and organs Food Acquisition Method Ingestive; absorptive Characteristic Features Elaborate life cycles Helminths (Parasitic Worms) Kingdom: Animalia ◦ Phylum: Platyhelminthes (flatworms) Class: trematodes (flukes) Class: cestodes (tapeworms) ◦ Phylum: Nematoda (roundworms) Characteristics of Helminths Reduced digestive system Reduced nervous system Reduced locomotion Complex reproduction Life Cycle of Helminths Monoecious (hermaphroditic) ◦ Male and female reproductive systems in one animal Dioecious ◦ Separate male and female Egg larva(e) adult Question Why are the drugs used to treat parasitic helminths often toxic to the host? 12-14 Platyhelminths- Trematodes Also called flukes Absorb food through a cuticle Schistosoma mansoni Tissue damage (granulomas) in response to eggs lodging in tissues African, Middle East, South America, Caribbean 2nd only to malaria in the # of people it kills or disables Granuloma Figure 23.28 Schistosomiasis. 8 Cercariae travel through circulatory system to intestinal blood vessels, where they mature into adults. 1 Definitive host Adult flukes Adult female flukes lay eggs. Male Mouth Female (size: 15–20 mm) Eggs Sucker Female Mouth Male 7 Free-swimming cercariae penetrate human skin, losing tail. (a) Male and female Cercaria (0.13 mm) 2 Eggs reach body of water after being excreted in human feces or urine. Egg (0.15 mm) Cercaria (0.33 mm) Intermediate host 6 3 Cercariae are released from the snail. 5 Miracidium reproduces in snail, forming several cercariae. 4 Miracidium penetrates snail. Miracidium (0.2 mm) schistosomes. The female lives in a groove on the ventral (lower) surface of the male schistosome (“split-body”), is continuously fertilized, and continuously lays eggs. The sucker is used by the male to attach to the host. Eggs hatch into free-swimming larvae (miracidia). (b) Life cycle of Schistosoma, cause of schistosomiasis. Platyhelminths- Cestodes Also called a tapeworm Scolex- head with suckers or hooks Absorb foods through cuticle Proglottidssegments; contains both female and male reproductive parts Taenia saginata Found in cattle (beef tapeworm) Human ingest the proglottids found in the meat Abdominal distress Nematoda Roundworms Complete digestive system Male and female Some are free living in soil Most common helminth infection Nector americanus Hookworm Attaches and feeds on blood and tissue Leads to anemia and lethargic behavior Ascaris lumbricodes Common in the SE US Absorb partially ingested food Can cause lung problems or blockages in the intestines, liver or pancreas Can come out of the anus, mouth, nose or navel Enterobius vermicularis Most common in the US Females lay their eggs around the anus and this causes itching. Eggs get transmitted by hands and close contact Scotch-Tape test diagnosis Figure 12.29 The pinworm Enterobius vermicularis. Mouth Intestine Mouth Ovary Genital pore Anus Genital pore Intestine Testis Spicules Egg (55 μm long) Anus Adult pinworm Female (8–13 mm long) Male (2–5 mm long) Larva Pinworm egg Arthropods as Vectors May transmit diseases (vectors) Kingdom: Animalia ◦ Phylum: Arthropoda (exoskeleton, jointed legs) Lice, fleas, mosquitoes Mites and ticks Arthropods as Vectors Mechanical transmission Biological transmission ◦ Microbe multiplies in vector Definitive host ◦ Microbe’s sexual reproduction takes place in vector Figure 12.31 Mosquito. Figure 12.32 Tick. Figure 12.33 Arthropod vectors. 2.5 mm 2.5 mm 2 cm Insert Fig 12.33 1 cm Human louse Rat flea Deer fly Kissing bug
