Inquiry into Life Eleventh Edition Sylvia S Mader

Inquiry into Life Eleventh Edition Sylvia S. Mader Chapter 28 Lecture Outline Prepared by: Wendy Vermillion Columbus State Community College 1 Copyright The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

28. 1 Viruses, viroids, and prions • Biology of viruses-noncellular, obligate parasites – Viral structure • 0. 2 microns in size, much smaller than bacteria • Many shapes- rods, blocks, polyhedrons • 2 basic parts – Outer capsid of protein subunits – Inner core of nucleic acid » Can be either double-stranded DNA. Single-stranded DNA, single-stranded RNA, or double-stranded RNA • Some viruses have an envelope surrounding capsid – Derived from host cell’s plasma membrane – Viral spikes-extensions of envelop for adherence 2

Viral structure • Fig. 28. 1 3

Viruses, viroids, and prions cont’d. • Viral reproduction – Highly specific for host cells • Spike and host cell membrane receptor fits like lock and key – Life cycle of typical animal virus has 6 steps • • • Attachment-spike binds to receptor Entrance-virus enters cell and uncoating occurs Replication-many copies of viral genome are made Biosynthesis-viral components synthesized Assembly-new virus particles assembled Budding-acquires an envelope with spikes – These steps are illustrated on the following slide – All Elephants Read Books At Borders (made by Period 7 20082009 bio class) 4

Life cycle of an animal virus • Fig. 28. 2 5

Viruses, viroids, and prions cont’d. • Latency – Viral genome of some viruses can lie dormant within host cell genome • Called a provirus • Viral DNA is replicated along with the host genome – Can lie dormant for years • Stress may stimulate provirus to enter biosynthesis stage – Retroviruses • Genome is in RNA • Enzyme reverse transcriptase transcribes RNA into DNA – This DNA is called c. DNA (copy DNA) • c. DNA can incorporate into host cell genome 6

Viruses, viroids, and prions cont’d. • Human viral diseases – Influenza and colds • Colds are caused by rhinoviruses • Flu is caused by influenza viruses • Many antigenic forms of both – Explains why flu vaccinations must be given each year as new antigenic forms appear 7

Influenza virus • Fig. 28. 3 8

Viruses, viroids, and prions cont’d. • Measles – Most contagious human disease – Spread by respiratory route – 7 -12 day incubation period before flu-like symptoms and rash appear • Major killer worldwide in non-vaccinated populations • MMR vaccine protects against measles • Herpes – Chronic viral infection that can remain latent • Herpes simplex type 1 -cold sores and fever blisters • Herpes simplex type 2 -genital herpes • Herpes zoster- chickenpox and shingles 9

Chickenpox • Fig. 28. 4 10

Viruses, viroids, and prions cont’d. • Drug control of human viral diseases – Difficult to develop drugs that affect viral reproduction without harming host cell – Antiviral drugs against HIV have been developed – Acyclovir is used against Herpes – Antibiotics are not effective against viruses 11

Viruses, viroids, and prions cont’d. • Viroids and prions – Also acellular pathogens – Viroids are naked RNA molecules which do not code for proteins • Infect plant cells and cause disease – Prions are rogue folded proteins-passed through ingestion of infected tissues • • • Derived from normal proteins in the brain Scrapie in sheep Mad cow disease in cattle Creutzfeld-Jakob disease in people Kuru- human to human transmission through cannibalism 12

28. 2 Bacteria and Archaea • Biology of bacteria – 3 basic shapes-cocci, bacilli, spirillum • Bacilli and cocci may be solitary or in clusters or chains – Bacterial structure • Plasma membrane • Many have a cell wall containing peptidoglycans – Differential stains like the Gram stain interact with cell wall components » Gram-positive bacteria-retain crystal violet (purple color) » Gram-negative bacteria-retain the counter stain safranin (red color) • Organelles as illustrated on the following slide 13

Typical bacterial cell • Fig. 28. 6 14

Bacteria and archaea cont’d. • Bacterial reproduction – Binary fission-after a period of growth a bacterial cell can replicate its genome and divide in half asexually – In harsh conditions, Gram-positive bacteria (and some Gram negatives) can form a resistant endospore – No sexual reproduction, but three mechanisms of genetic recombination • Conjugation-cell passes DNA through a sex pillus • Transformation-bacterium takes up DNA from environment released by dead bacteria • Transduction-viruses carry bacterial DNA from cell to cell 15

Binary fission • Fig. 28. 7 16

Bacteria and archaea cont’d. • Bacterial metabolism – Most are heterotrophic • Some are anaerobic and cannot use oxygen • Some are photosynthetic • Cyanobacteria- have chlorophyll a and undergo photosynthesis – Some are chemosynthetic • Use chemicals to generate sugar 17

Cyanobacteria • Fig. 28. 8 18

Bacteria and archaea cont’d. • Environmental and medical aspects of bacteria – Bacteria are decomposers • Break down organic matter and make inorganic nutrients available for plants 19

Bacteria and archaea cont’d. • Environmental and medical aspects of bacteria – Food processing – Antibiotic production – Genetically engineered bacteria produce many products such as insulin and vaccines 20

Bacteria and archaea cont’d. • Bacterial diseases in humans – Streptococcus infections • • • Cause more disease than any other genus Pharyngitis-most common and mild strep disease Streptococcus pneumoniae-important agent in bacterial pneumonia Streptococcus mutans- contributes to dental cavities Streptococcus pyogenes-causes the most disease of any strep – Impetigo in infants- mild skin disease – Rheumatic fever- from endotoxins – Necrotizing fasciitis-”flesh-eating” bacteria 21

Streptococcus pyogenes • Fig. 28. 9 22

Bacteria and archaea cont’d. • Bacterial diseases in humans -Tuberculosis -Highest mortality worldwide of any disease -Active lesions in lung cause tubercles - Food poisoning -Salmonella-symptoms take several days to weeks to develop -Staphlyococcus- acts quickly due to toxin production -Clostridium botulinum- produces one of the most deadly toxins on Earth; anaerobic, and can survive in improperly canned foods 23

Tuberculosis • Fig. 28. 10 24

Bacteria and archaea cont’d. • Drug control of human bacterial diseases – Antibiotics interfere with metabolic processes unique to bacteria • Inhibition of synthesis of bacterial proteins • Should not harm human cells – Problems related to antibiotic therapy • • Potentially fatal allergic reactions Killing off of normal flora Prevention of natural immunity Bacterial resistance 25

Bacteria and archaea cont’d. • Biology of archae – Very different from the bacteria – Inhabit extreme environments • Extreme thermophiles- live in extremely high temperatures • Extreme thermoacidophiles- line in habitats with high temperature and low p. H • Halophiles- live in salty habitats • Methanogens- anaerobic environments 26

Comparison of domains Archae and Eukarya • Table 28. 1 27

Extreme habitats • Fig. 28. 11 28

28. 3 Protists • Overview – Very diverse group, widespread in moist environments – Generally unicellular 29

Protists cont’d. • Biology and diversity of algae – Can be unicellular, colonial, or filamentous – Components of phytoplankton • • Important food source for heterotrophs Oxygen-producers Symbiotic relationships with fungi-lichens Green algae- have chlorophyll a and b 30

Representative green algae • Fig. 28. 12 31

Protists cont’d. • Diatoms – – Most numerous unicellular algae in the oceans Component of phytoplankton Intricate shells of silica Diatomaceous earth- shells of diatoms • Dinoflagellates – Have cellulose plates and 2 flagella – Component of phytoplankton • Can produce neurotoxin- red tides – Generally photosynthetic – Some have bioluminescence 32

Diatom shells • Fig. 28. 13 33

Dinoflagellates • Fig. 28. 14 34

Protists cont’d. • Red algae (Rhodophyta) – Mainly multicellular seaweeds – Contain red pigments as well as chlorophyll – Produce useful gelling agents • Agar • Carageenan • Brown algae (Phaeophyta) – Multicellular seaweeds, kelps – Has accessory pigments ranging in color from brown to black – Harvested for food in some parts of the world 35

Red alga • Fig. 28. 15 36

Brown alga • Fig. 28. 16 37

Protists cont’d. • Euglenoids – Freshwater unicellular organisms – Most have chloroplasts but some do not; chloroplasts are surrounded by 3 membranes instead of 2 – Have 2 flagella – Have a photoreceptor called an eyespot 38

Euglena • Fig. 28. 17 39

Protists cont’d. • Biology and diversity of protozoans (animal protists) – Overview • Commonly divided and classified by mechanism of locomotion • Wide distribution – Aquatic habitats- zooplankton – Parasites • Variable cell structure – Contractile vacuoles- regulate water balance – Some produce cysts for survival in adverse conditions 40

Protists cont’d. • Classification of protozoans by motility – The ciliates (Ciliophorans) • Move by means of cilia – Cilia also aid in prey capture and feeding – Cilia moves food to gullet, engulfed in phagocytic vacuole • Examples: Paramecium and Stentor 41

Ciliates • Fig. 28. 18 42

Protists cont’d. • Protozoans cont’d. – Ameboids • • • Move by pseudopodia Aquatic, freshwater and saltwater forms Component of zooplankton Feed by phagocytosis Examples – Entamoeba sp. - causes amebic dysentary – Foraminiferans and radiolarians- have a skeleton called a test » Deposits indicate presence of oil on land sea » Used to date sedimentary rocks » Deposits form White Cliffs of Dover 43

Ameboids • Fig. 28. 19 44

Protists cont’d. • Zooflagellates – Colorless heterotrophs – Move by flagella – Most are symbiotic, many parasitic • Trypanosoma- causes African sleeping sickness – Tsetse fly is vector – Lives in bloodstream of host • Chagas disease- transmitted by the kissing bug • Giardia lamblia- giardiasis- severe diarrhea 45

Trypanosome • Fig. 28. 20 46

Protists cont’d. • Sporozoans – Generally nonmotile – Malaria- most widespread and dangerous sporozoan disease • Plasmodium vivax- spread by the Anopheles mosquito – Life cycle illustrated on the following slide 47

Life cycle of Plasmodium vivax • Fig. 28. 21 48

Protists cont’d. • Other sporozoan diseases – Toxoplasmosis • oocysts commonly transmitted by infected cats – For most people, it produces only mild flu-like symptoms – In pregnant women it can infect the fetus and cause neurological damage – Cryptosporidium –causes mild gastroenteritis in most, but can be fatal in people who are immunosuppressed • Passed in feces of infected animals • Can pass through water filtration processes and is unaffected by chlorination 49

Protists cont’d. • Molds as protists – Water molds and slime molds are classified as protists – Both have flagellated cells – Water molds • Saprophytic, live off dead matter • Have a filamentous body with cell walls of cellulose 50

Protists cont’d. • Molds as protists cont’d. – Slime molds • Feed on dead plant material and bacteria • Plasmodial (acellular) slime molds- exist as a plasmodium – Diploid multinucleate cytoplasmic mass with a slimy sheath (the Blob!) – Crawls along forest floor and phagocytizes dead organic matter 51

Plasmodial slime molds • Fig. 28. 22 52

28. 4 Fungi • Overview of fungi – – – True multicellularity with differentiation Strict heterotrophs Release enzymes into environment- digestion is extracellular Most are saprophytic (feed on dead material) Along with bacteria, fungi are important as decomposers • Biology of fungi – Body- mass of filaments called a mycelium • Each filament is a hypha- increase surface area for absorption – Some have crosswalls between cells-septa 53

Fungal mycelia and hyphae • Fig. 28. 23 54

Fungi cont’d. • Fungal cell structure – Cell walls contain chitin • Polymer of glucose – Each glucose has an amino group attached • Found in exoskeletons of animals • Move toward food source by growing toward it – Hyphae can grow as much as a meter per day! 55

Fungi cont’d. • Fungal reproduction – Adapted to dry land-produce wind-blown spores • Can reproduce sexually or asexually 56

Fungi cont’d. • Diversity of fungi-classified by mode of sexual reproduction – Phylum Zygomycota-bread molds • Saprotrophs and parasites • Rhizopus stolonifer –black bread mold is a familiar zygospore fungus – life cycle is illustrated on following slide 57

Black bread mold Rhizopus stolonifer • Fig. 28. 25 58

Fungi cont’d. • Sac fungi- Phylum Ascomycota – Sexual reproductive structure called an ascus – In asexual reproduction, the asexual spores are called conidia – Unicellular ascomycetes are often called yeasts • Unequal binary fission- called budding • Fermentation by some yeasts produces CO 2 and ethanol – Used to make beer, wine, and bread 59

Sexual reproduction in sac fungi • Fig. 28. 26 60

Asexual reproduction in sac fungi • Fig. 28. 27 61

Fungi cont’d. • Club fungi- Phylum Basidiomycota – Characteristic sexual reproductive structure is called a basidium • Contained within a basidiocarp – Edible part of a mushroom is the basidiocarp – Sexual reproduction is most prominent in this group 62

Sexual reproduction in club fungi • Fig. 28 63

Fungi cont’d. • Imperfect fungi- Phylum Deuteromycota – Includes many familiar fungi – Aspergillis- used to make soy sauce from fermenting soy beans – Penicillium- original source of penicillin • Penicillium roquefortii and camemberti- used in making blue cheeses 64

Blue cheese • Fig. 28. 29 65

Fungi cont’d. • Environmental importance of fungi – Fungi and photosynthesizers • Lichens- associations between fungi and cyanobacteria or green algae • Efficient at acquiring nutrients and moisture-can colonize poor soil, rocky surfaces – Produce organic matter and create new soil 66

Lichen morphology • Fig. 28. 30 67

Fungi cont’d. • Environmental aspects, cont’d. – Mycorrhizal fungi • Mutualistic relationships with plant roots – Helps plants to grow more successfully in poor soils • Fungi can live on the outside surface of roots, or it can penetrate the root tissues – Plant provides organic nutrients to the fungus – Fungus brings water and minerals to the plant » Hyphae provide lots of surface area for water absorption 68

Fungi cont’d. • Medical aspects of fungi – Fungal diseases of plants • Many enter through the stomata of the leaves or through a wound • Smuts and rusts- sac fungi that parasitize cereal crops – Fungal diseases of humans • Mycoses – Cutaneous- affect only the skin – Subcutaneous-deeper skin layers – Systemic-spread throughout the body • Many fungal diseases are acquired from the environment – Ringworm from soil fungi for example 69

Smuts and rusts • Fig. 28. 31 70

Fungi cont’d. • Human fungal diseases – Tineas • Skin infections-can occur anywhere on the skin – Athlete’s foot- scaling, peeling, and itching between toes – Ringworm- redness and inflammation due to enzymes released by the fungus; extends outward in a ring-shape – Histoplasmosis • • Caused by Histoplasmosis capsulatum; common in the Midwest Carried in bird droppings Mild flu-like symptoms, fungus lives in cells of the immune system Healed lesions in the lungs calcify 71

Human diseases caused by fungi • Fig. 28. 32 72

Fungi cont’d. • Control of fungi – Fungi more closely resemble animal cells than bacteria – Makes it harder to develop antibiotics that will kill fungi and not the host – Fungi synthesize steroids differently-fungicides are directed at steroid biosynthesis 73