The Eukaryotes: Fungi, Algae, Protozoa, and Helminths

Transcription

1 PowerPoint Lecture Presentations prepared by Bradley W. Christian, McLennan Community College C H A P T E R 12 The Eukaryotes: Fungi, Algae, Protozoa, and Helminths

2 Fungi Mycology: the study of fungi Chemoheterotrophs Decompose organic matter Aerobic or facultative anaerobic

3 Table 12.1 Selected Features of Fungi and Bacteria Compared

4 Vegetative Structures Molds and fleshy fungi The fungal thallus (body) consists of hyphae filaments; a mass of hyphae is a mycelium Septate hyphae: contain cross-walls Coenocytic hyphae: do not contain septa Vegetative hyphae obtain nutrients while aerial hyphae are involved with reproduction

5 Figure 12.2 Characteristics of fungal hyphae. Cell wall Pore Nuclei Septum Spore Septate hypha Coenocytic hypha Growth of a hypha from a spore

6 Vegetative Structures Yeasts Nonfilamentous and unicellular Budding yeasts divide unevenly Fission yeasts divide evenly Dimorphic fungi Yeastlike at 37 C and moldlike at 25 C

7 Life Cycle Fungi reproduce sexually and asexually via the formation of spores that detach from the parent and germinate into a new mold

8 Life Cycle Asexual spores Produced via mitosis and cell division; formed by the hyphae of one organism Conidiospore: not enclosed in a sac Arthroconidia: fragmentation of septate hyphae Blastoconidia: buds of the parent cell Chlamydoconidium: spore within a hyphal segment Sporangiospore: enclosed in a sac

9 Life Cycle Sexual spores Fusion of nuclei from two opposite mating strains Three phases of sexual reproduction: Plasmogamy: haploid donor cell nucleus (+) penetrates cytoplasm of recipient cell ( ) Karyogamy: + and nuclei fuse and form diploid zygote Meiosis: diploid nucleus produces haploid nuclei (sexual spores)

10 Nutritional Adaptations Grow better at ph of 5 Grow in high sugar and salt concentration; resistant to osmotic pressure Can grow in low moisture content Can metabolize complex carbohydrates

11 Medically Important Fungi Zygomycota Microsporidia Ascomycota Basidiomycota

12 Zygomycota Conjugation fungi Coenocytic hyphae Produced asexually: sporangiospore Produced sexually: zygospore Forms when nuclei of two similar cells fuse

13 Figure 12.7 The life cycle of Rhizopus, a zygomycete. Sporangiospore Spores are released from sporangium. Sporangium bursts to release spores. Spore germinates to produce hyphae. Spore germinates to produce hyphae. Zygote produces a sporangium. Aerial hypha produces a sporangium. Asexual reproduction Sporangium Sporangiophore Vegetative mycelium grows. Sexual reproduction Karyogamy and meiosis. Gametes form at tip of hypha. Zygospore forms. Plasmogamy. Sporangiospores Zygosporangium containing zygospore

14 Microsporidia No sexual reproduction is observed, but probably occurs in a host No mitochondria Obligate intracellular parasites

15 Figure 12.8 The life cycle of Encephalitozoon, a microsporidian. Spores are ingested or inhaled. Mature spores Vacuole New spores are released. Spore injects tube into host cell. Host cell Asexual reproduction Cytoplasm and nucleus enter. Cytoplasm breaks up around nuclei to form spores. Cytoplasm grows, and nuclei reproduce.

16 Ascomycota Sac fungi; septate hyphae Teleomorphic fungi Produce sexual and asexual spores Some are anamorphic Lost ability to sexually reproduce Produced asexually: conidiospore Produced sexually: ascospore Nuclei morphologically similar or dissimilar fuse in a saclike ascus

17 Figure 12.9 The life cycle of Talaromyces, an ascomycete. Conidia are released from conidiophore. Conidium germinates to produce hyphae. Ascospore germinates to produce hyphae. Ascus opens to release ascospores. Asexual reproduction Vegetative mycelium grows. Sexual reproduction Meiosis then mitosis. Hypha produces conidiophore. Ascus Conidia Karyogamy. Plasmogamy. Ascospore Conidiophore

18 Basidiomycota Club fungi; septate hyphae Produced asexually: conidiospores Produced sexually: basidiospores Formed externally on a base pedestal called a basidium

19 Figure A generalized life cycle of a basidiomycete. Hyphal fragment breaks off vegetative mycelium. Fragment grows to produce new mycelium. Basidiospore germinates to produce hyphae. Basidiospores are discharged. Basidiospores mature. Basidium Asexual reproduction Sexual reproduction Vegetative mycelium grows. Plasmogamy. Basidiospores are formed by meiosis. Fruiting structure ("mushroom") develops.

20 Fungal Diseases Mycosis: fungal infection Systemic mycoses: deep within the body Subcutaneous mycoses: beneath the skin Cutaneous mycoses: affect hair, skin, and nails Superficial mycoses: localized (e.g., hair shafts) Opportunistic mycoses: fungi harmless in normal habitat but pathogenic in a compromised host

21 Table 12.2 Characteristics of Some Pathogenic Fungi (1 of 2)

22 Table 12.2 Characteristics of Some Pathogenic Fungi (2 of 2)

23 Economic Effects of Fungi Saccharomyces cerevisiae: bread, wine, hepatitis B vaccine Trichoderma: cellulase Taxomyces: taxol Entomophaga: biocontrol Coniothyrium minitans: kills fungi on crops Paecilomyces: kills termites

24 Lichens Mutualistic combination of a green alga (or cyanobacterium) and fungus Crustose encrusted on the substratum Foliose leaflike Fruticose fingerlike Thallus (body) of lichens are made of: Medulla hyphae grown around algal cells Rhizines (holdfasts) hyphae projections below the body Cortex protective coating over the algal layer

25 Figure 12.11b Lichens. Fungus Alga Cortex Algal layer Medulla Fungal hyphae Cortex Rhizine Lichen thallus

26 Lichens Alga produces and secretes carbohydrates; fungus provides holdfast Economic importance Dyes Antimicrobial (Usnea) Litmus Food for herbivores

27 Algae Not a taxonomic group Unicellular or filamentous photoautotrophs Lack roots, stems, and leaves Mostly aquatic Water is necessary for growth and reproduction

28 Table 12.3 Characteristics of Selected Algae

29 Characteristics of Algae Locations depend on nutrient availability, wavelengths of light, and surfaces to attach Thallus: body of multicellular algae Consists of holdfasts, stipes, and blades

30 Photic zone Figure 12.12a Algae and their habitats. SURFACE Sublittoral zone Unicellular green algae, diatoms, dinoflagellates Littoral zone Green algae, cyanobacteria, euglenoids LAND Red Orange Multicellular green algae Brown algae Yellow Violet Blue Red algae Algal habitats

31 Characteristics of Algae All reproduce asexually Multicellular algae can fragment or reproduce sexually via alternation of generations

32 Figure 12.13b Green algae. Flagella Mitosis Meiosis Zygote formation Fertilization Growth Nucleus Sexual reproduction Chloroplast Eyespot Stored starch Asexual reproduction Cell wall Gamete formation Growth Life cycle of a unicellular green alga (Chlamydomonas)

33 Selected Phyla of Algae Brown algae (kelp) Cellulose and alginic acid cell walls Multicellular and macroscopic Produce algin thickener used in foods

34 Selected Phyla of Algae Red algae Have branched thalli Most are multicellular Harvested for agar and carrageenan Some produce a lethal toxin

35 Selected Phyla of Algae Green algae Cellulose cell walls Unicellular or multicellular Chlorophyll a and b Store starch Gave rise to terrestrial plants

36 Selected Phyla of Algae Diatoms Pectin and silica cell walls Unicellular or filamentous Store oil Produce domoic acid cause neurological disease

37 Selected Phyla of Algae Dinoflagellates Cellulose in plasma membrane Unicellular Neurotoxins (saxitoxins) cause paralytic shellfish poisoning

38 Selected Phyla of Algae Oomycota (water molds) Cellulose cell walls Chemoheterotrophic Produce zoospores Decomposers and plant parasites Phytophthora infestans was responsible for Irish potato blight P. cinnamoni infects Eucalyptus P. ramorum causes "sudden oak death"

39 Roles of Algae in Nature Fix CO 2 into organic molecules Produce 80% of Earth's O 2 Algal blooms are increases in planktonic algae that can result in toxin release or die and consume oxygen Oil production Symbionts of animals

40 Protozoa Unicellular eukaryotes Inhabit water and soil Animal-like nutrition Complex life cycles

41 Protozoa Feeding and growing form is a trophozoite Asexual reproduction is by fission, budding, or schizogony (multiple fission) Sexual reproduction is by conjugation Some produce a cyst to survive adverse conditions

42 Characteristics of Protozoa Require a large supply of water Many have an outer protective pellicle, requiring specialized structures to take in food Ciliates wave cilia toward mouthlike cytosome Amebae phagocytize food Food is digested in vacuoles and wastes eliminated through an anal pore

43 Medically Important Protozoa Feeding grooves (Excavata) Diplomonads Parabasalids Euglenozoa Amebae Apicomplexa Ciliates

44 Medically Important Protozoa Diplomonads No mitochondria; multiple flagella Parabasalids Undulating membrane; no cyst stage Euglenozoa Photoautotrophs or facultative chemotrophs Hemoflagellates transmitted by bites of blood-feeding insects

45 Amebae Move by extending pseudopods Entamoeba histolytica causes amebic dysentery Acanthamoeba infects corneas and causes blindness Balamuthia granulomatous amebic encephalitis

46 Apicomplexa Nonmotile Obligate intracellular parasites Complex life cycles Toxoplasma gondii transmitted by cats; causes fetal infections Cryptosporidium transmitted via feces; causes waterborne illness

47 Apicomplexa Plasmodium causes malaria Sexually reproduces in the Anopheles mosquito A mosquito injects a sporozoite into its bite, and the sporozoite undergoes schizogony in the liver; merozoites are produced Merozoites infect red blood cells, forming a ring stage inside the cell Red blood cells rupture, and merozoites infect new red blood cells

48 Figure The life cycle of Plasmodium vivax, the apicomplexan that causes malaria. Resulting sporozoites migrate to salivary glands of mosquito. Sporozoites in salivary gland Infected mosquito bites human; sporozoites migrate through bloodstream to liver of human. Sporozoites undergo schizogony in liver cell; merozoites are produced. In mosquito's digestive tract, gametocytes unite to form zygote. Zygote Sexual reproduction Female gametocyte Male gametocyte Male Gametocytes Asexual reproduction Merozoites released into bloodstream from liver may infect new red blood cells. Merozoite develops into ring stage in red blood cell. Intermediate host Another mosquito bites infected human and ingests gametocytes. Female Ring stage grows and divides, producing merozoites. Merozoites are released when red blood cell ruptures; some merozoites infect new red blood cells, and some develop into male and female gametocytes.

49 Ciliates Move by cilia arranged in precise rows Balantidium coli is the only human parasite; causes dysentery

50 Figure Ciliates. Pellicle Cytostome Food vacuoles Cilia Contractile vacuole Macronucleus Micronucleus Anal pore Paramecium Stalk Cilium Cytostome Vorticella

51 Slime Molds Cellular slime molds Resemble ameba Ingest fungi and bacteria by phagocytosis Cells aggregate to form stalks and spore caps that differentiate into spores

52 Figure The generalized life cycle of a cellular slime mold. Spore caps Spore Ameba reproduces. Nucleus Stalk (1 mm) Spore is released. Ameba germinates from spore. camp Amebae move toward camp signal given off by one ameba. camp Cells in spore cap form spores. Fruiting body with spore cap forms. Slug stops migrating and begins to form stalk in differentiation stage. Asexual reproduction Sheath forms to create migration stage (slug) (0.5 mm). camp Amebae aggregate.

53 Slime Molds Plasmodial slime molds Mass of protoplasm with multiple nuclei; moves as a giant ameba Cytoplasmic streaming protoplasm moves and changes speed and direction to distribute oxygen and nutrients

54 Helminths Parasitic worms Two phyla: Platyhelminthes (flatworms) Nematoda (roundworms)

55 Characteristics of Helminths Multicellular eukaryotic animals Specialized to live in hosts May lack digestive system Reduced nervous system Reduced or lacking locomotion Complex reproductive system

56 Life Cycle Dioecious Separate male and female Monoecious (hermaphroditic) Male and female reproductive systems in one animal Egg larva(e) adult

57 Platyhelminths Trematodes (flukes) Flat, leaf-shaped Ventral and oral sucker Absorb food through cuticle covering Paragonimus spp. lung fluke Schistosoma blood fluke

58 Figure The life cycle of the lung fluke, Paragonimus spp. In crayfish, cercaria encysts to produce metacercaria. Infected crayfish is eaten by human, and metacercaria develops into adult fluke. Hermaphroditic adult fluke releases eggs into human lung. Adult fluke ( mm long) Metacercaria ( mm) Asexual reproduction Definitive host Sexual reproduction Eggs Eggs reach water after being excreted in feces. Intermediate host Cercaria leaves snail and enters crayfish. Cercaria Intermediate host Free-swimming miracidium enters snail. Miracidium develops in egg and hatches from egg. Cercaria (0.5 mm long) Redia Inside snail, miracidium develops into redia, which reproduces asexually to produce rediae; several cercariae develop within redia. Miracidium (0.8 mm long)

59 Platyhelminths Cestodes (tapeworms) Scolex head that has suckers for attachment Absorb food through cuticle Proglottids body segments; contain male and female reproductive organs

60 Figure General anatomy of an adult tapeworm. Scolex Hooks Sucker Neck Testis Genital pore Ovary Mature proglottid will disintegrate and release eggs

61 Cestodes Humans as definitive hosts Eggs from proglottids are ingested, hatch into larvae, and bore into the intestinal wall Produce cysticerci Taenia solium pork tapeworm

62 Cestodes Humans as intermediate hosts Eggs are ingested and hatch in the intestine Larvae migrate to the liver or lungs and develop a hydatid cyst Echinococcus granulosus

63 Figure The life cycle of the tapeworm, Echinococcus spp. Adult tapeworm releases eggs. Intermediate host Scoleces from cyst attach to intestine and grow into adults. Adult tapeworm Egg (30 38lm) Human intermediate host ingests eggs. Dead end. Scolex Intermediate host Sexual reproduction Asexual reproduction Intermediate host ingests eggs. Definitive host eats intermediate host, ingesting cysts. Definitive host Hydatid cyst Larva Eggs hatch, and larvae migrate to liver or lungs. Brood capsule Scolex Larvae develop into hydatid cysts.

64 Nematodes Roundworms Cylindrical; complete digestive system Dioecious; males contain spicules Free-living and parasitic

65 Nematodes Eggs infective for humans Ascaris lumbricoides infects human intestines Baylisascaris procyonis raccoon roundworm Trichuris trichiura whipworm Enterobius vermicularis pinworm

66 Figure The pinworm, Enterobius vermicularis. Mouth Intestine Ovary Mouth Genital pore Anus Intestine Testis Anus Genital pore Spicules Egg (55 m long) Adult pinworm Female (8 13 mm long) Male (2 5 mm long) Pinworm egg Larva

67 Nematodes Larvae infective for humans Strongyloides reemerging infection Necator americanus and Ancylostoma duodenale hookworms; enter the skin and are carried to the intestines Dirofilaria immitis spread by mosquitoes; causes heartworm

68 Arthropods as Vectors Arthropods are animals with segmented bodies, hard external skeletons, and jointed legs Vectors are arthropods that carry pathogenic microorganisms Representative classes: Arachnida eight legs Crustacea four antennae Insecta six legs

69 Arthropods as Vectors Mechanical transmission Biological transmission Pathogen multiplies in the vector Definitive host Microbe's sexual reproduction takes place in the vector