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Inquiry into Life Eleventh Edition Sylvia S. Mader

28-2. 28.1 Viruses, viroids, and prions. Biology of viruses-noncellular, obligate parasitesViral structure0.2 microns in size, much smaller than bacteriaMany shapes- rods, blocks, polyhedrons2 basic partsOuter capsid of protein subunitsInner core of nucleic acidCan be either double-stranded DNA. Single-stranded DNA, single-stranded RNA, or double-stranded RNASome viruses have an envelope surrounding capsidDerived from host cell's plasma membraneViral spikes-extensions of envelop for adherence.

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Inquiry into Life Eleventh Edition Sylvia S. Mader

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    1. 28-1 Inquiry into Life Eleventh Edition Sylvia S. Mader Chapter 28 Lecture Outline

    2. 28-2 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

    3. 28-3 Viral structure Fig. 28.1

    4. 28-4 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 RNA 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

    5. 28-5 Life cycle of an animal virus Fig. 28.2

    6. 28-6 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 cDNA (copy DNA) cDNA can incorporate into host cell genome

    7. 28-7 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 Antigenic drift-re-assortment and combination of RNA from more than one viral form Explains why flu vaccinations must be given each year as new antigenic forms appear

    8. 28-8 Influenza virus Fig. 28.3

    9. 28-9 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

    10. 28-10 Chickenpox Fig. 28.4

    11. 28-11 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

    12. 28-12 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

    13. 28-13 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 Gram-negative bacteria-retain the counter stain safranin; high lipopolysaccarhide content causes crystal violet to be washed out Organelles as illustrated on the following slide

    14. 28-14 Typical bacterial cell Fig. 28.6

    15. 28-15 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-”male” cell passes DNA to “female” through a sex pillus Transformation-bacterium takes up DNA from environment released by dead bacteria Transduction-viruses carry bacterial DNA from cell to cell

    16. 28-16 Binary fission Fig. 28.7

    17. 28-17 Bacteria and archaea cont’d. Bacterial metabolism Most are heterotrophic Some are anaerobic and cannot use oxygen as final electron acceptor Sulfate reducers-transfer electrons to sulfate Denitrifying bacteria use nitrate Some are photosynthetic Cyanobacteria- have chlorophyll a and undergo photosynthesis Other types split hydrogen sulfide instead of water to produce sulfur as a by-product Some are chemosynthetic Reduce carbon dioxide to an organic compound using electrons from ammonia, hydrogen gas, hydrogen sulfide, or certain minerals such as iron

    18. 28-18 Cyanobacteria Fig. 28.8

    19. 28-19 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 Essential to biogeochemical cycles Cyanobacteria produce oxygen from photosynthesis First colonizers of rocky habitats Many capable of both carbon and nitrogen fixation Form a symbiotic relationship with fungi in lichens

    20. 28-20 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

    21. 28-21 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 caries Streptococcus pyogenes-causes the most disease of any strep Impetigo in infants- mild skin disease Rheumatic fever- from endotoxins Necrotizing fasciitis-”flesh-eating” bacteria

    22. 28-22 Streptococcus pyogenes Fig. 28.9

    23. 28-23 Bacteria and archaea cont’d. Bacterial diseases in humans Tuberculosis Highest mortality worldwide of any disease 1/3 of the world’s population is infected Caused by Mycobacterium tuberculosis Active lesions in lung cause tubercles from immune response Become calcified 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

    24. 28-24 Tuberculosis Fig. 28.10

    25. 28-25 Bacteria and archaea cont’d. Bacterial diseases in humans Chlamydia infections Chlamydia trachomatis small intestinal parasite causing variety of diseases Blindness Venereal disease

    26. 28-26 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

    27. 28-27 Bacteria and archaea cont’d. Biology of archae Very different from the bacteria Archaea are more closely related to Eukarya based on nucleic acid similarities Inhabit extreme environments Extreme thermophiles- live in extremely high temperatures Extreme thermoacidophiles- line in habitats with high temperature and low pH Halophiles- live in salty habitats Methanogens- anaerobic environments

    28. 28-28 Comparison of domains Archae and Eukarya Table 28.1

    29. 28-29 Extreme habitats Fig. 28.11

    30. 28-30 Bacteria and archaea cont’d. Archaeal structure and metabolism Structure 0.1-15 microns in size DNA genome is a single, closed circular molecule Gram-positive archaea have thick polysaccarhide cell wall Gram-negative archaea have a protein surface layer Cell membranes-single lipid layer which may be highly branched Chemical characteristics make them acid and heat tolerant Reproduce by binary fission

    31. 28-31 Bacteria and archaea cont’d. Archaeal structure and metabolism cont’d. Metabolism Some are heterotrophs, some are autotrophs Halophiles-unique photopigment resembling pigment in human retina Many are obligate anaerobes Methanogens reduce carbon dioxide to methane Found in swamps, lake sediments, hot springs, and digestive tracts of animals Methane can be used for fuel, also a greenhouse gas

    32. 28-32 28.3 Protists Overview Very diverse group, widespread in moist environments Generally unicellular Have combination of characteristics not found in other eukaryotic kingdoms Have complicated life cycles that allow survival in adverse conditions Have some specialized organelles not found in other eukaryotes

    33. 28-33 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 Store carbohydrates in the form of starch within pyrenoids Cells walls of cellulose Unicellular green algae-Chlamydomonas filamentous-Spirogyra Colonial- Volvox

    34. 28-34 Representative green algae Fig. 28.12

    35. 28-35 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

    36. 28-36 Diatom shells Fig. 28.13

    37. 28-37 Dinoflagellates Fig. 28.14

    38. 28-38 Protists cont’d. Red algae Mainly multicellular seaweeds Contain red and blue pigments as well as chlorophyll Produce useful gelling agents Agar Carageenan Brown algae Multicellular seaweeds, kelps Has accessory pigments ranging in color from brown to black Sargasso Sea-has large floating mats of brown algae Harvested for food in some parts of the world Also as a source of algin-gelatinous product used in foods

    39. 28-39 Red alga Fig. 28.15

    40. 28-40 Brown alga Fig. 28.16

    41. 28-41 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 Pyrenoids-contain an unusual carbohydrate polymer Cell membrane is surrounded by a flexible pellicle-allows movement

    42. 28-42 Euglena Fig. 28.17

    43. 28-43 Protists cont’d. Biology and diversity of protozoans Overview Usually motile eukaryotic unicellular heterotrophic protists Commonly divided and classified by mechanism of locomotion Wide distribution Aquatic habitats- zooplankton Parasites Variable cell structure Some have more than one nucleus Contractile vacuoles- regulate water balance Some produce cysts for survival in adverse conditions

    44. 28-44 Protists cont’d. Classification of protozoans by motility The ciliates Move by means of cilia Cilia also aid in prey capture and feeding Cilia moves food to gullet, engulfed in phagocytic vacuole Merges with lysosome and digested Examples: Paramecium and Stentor

    45. 28-45 Ciliates Fig. 28.18

    46. 28-46 Protists cont’d. Protozoans cont’d. Ameboids Move by pseudopodia Aquatic, freshwater and saltwater forms Component of zooplankton Feed by phagocytosis Examples Ameba proteus- free-living freshwater ameba Entamoeba sp.- causes amebic dysentary Foraminiferans and radiolarians- have a skeleton called a test Deposits indicate presence of oil on land and sea Used to date sedimentary rocks Deposits form White Cliffs of Dover

    47. 28-47 Ameboids Fig. 28.19

    48. 28-48 Protists cont’d. Zooflagellates (mastigophora) 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

    49. 28-49 Trypanosome Fig. 28.20

    50. 28-50 Protists cont’d. Sporozoans Generally nonmotile with complex life cycles Intercellular or intracellular parasites Produce resistant spores Malaria- most widespread and dangerous sporozoan disease Plasmodium vivax- spread by the Anopheles mosquito Life cycle illustrated on the following slide

    51. 28-51 Life cycle of Plasmodium vivax Fig. 28.21

    52. 28-52 Protists cont’d. Other sporozoan diseases Toxoplasmosis Toxoplasma gondii- 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

    53. 28-53 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 Produce flagellated spores during asexual reproduction During sexual reproduction, produce eggs and sperm

    54. 28-54 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 Crawls along forest floor and phagocytizes dead organic matter Plasmodium produces sporangia which produce resistant spores Spores germinate to form flagellated cells and amoeboid cells These fuse and develop into a new plasmodium

    55. 28-55 Plasmodial slime molds Fig. 28.22

    56. 28-56 Protists cont’d. Molds as protists cont’d. Cellular slime molds Exist as individual amoeboid cells Common soil decomposers When food is scarce, they aggregate together to form a pseudoplasmodium This gives rise to sporangia which produces spores Spores germinate releasing haploid amoeboid cells

    57. 28-57 28.4 Fungi Overview of fungi True multicellularity with differentiation Strict heterotrophs Release enzymes into environment- digestion is extracellular Most are saprophytic 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 Nonseptate fungi lack crosswalls between cells-multinucleate

    58. 28-58 Fungal mycelia and hyphae Fig. 28.23

    59. 28-59 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 Energy reserve is glycogen like animal cells Move toward food source by growing toward it Hyphae can grow as much as a meter per day!

    60. 28-60 Fungi cont’d. Fungal reproduction Adapted to dry land-produce wind-blown spores Haploid reproductive cell- germinates and develops into new mycelium-asexual Sexual reproduction-conjugation of two different mating types Designated as + and – Dikaryonic state-in some, the + and – nuclei do not fuse for long periods of time After fusion of nuclei a zygote forms- undergoes meiosis Produces haploid spores and cycle begins again

    61. 28-61 Dispersal of spores Fig. 28.24

    62. 28-62 Fungi cont’d. Diversity of fungi-classified by mode of sexual reproduction Zygospore fungi- Phylum Zygomycota Saprotrophs and parasites Rhizopus stolonifer –black bread mold is a familiar zygospore fungus life cycle is illustrated on following slide Note formation of a zygospore from fusion of + and - hyphae

    63. 28-63 Black bread mold Rhizopus stolonifer Fig. 28.25

    64. 28-64 Fungi cont’d. Sac fungi- Phylum Ascomycota Sexual reproductive structure called an ascus Asci are enclosed within an ascocarp Ascocarp develops after fusion of + and – hyphae Union of + and – nuclei produces and ascus Ascus produces spores by meiosis 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 CO2 and ethanol Used to make beer, wine, and bread

    65. 28-65 Sexual reproduction in sac fungi Fig. 28.26

    66. 28-66 Asexual reproduction in sac fungi Fig. 28.27

    67. 28-67 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 Forms after fusion of + and – hyphae Sexual reproduction is most prominent in this group Asexual reproduction can occur by asexual spores called conidia

    68. 28-68 Sexual reproduction in club fungi Fig. 28.28

    69. 28-69 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 Deuteromycetes always reproduce asexually Produce conidia on aerial hyphae Sexual stage has not been identified and may not exist

    70. 28-70 Blue cheese Fig. 28.29

    71. 28-71 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 3 characteristic forms- crustose, foliose, fruticose Body of lichen has 3 layers-fungi form top and bottom layers and protect middle layer of photosynthetic cells Protects photosynthesizer and delivers water Photosynthesized gives the fungus nutrients

    72. 28-72 Lichen morphology Fig. 28.30

    73. 28-73 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

    74. 28-74 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

    75. 28-75 Smuts and rusts Fig. 28.31

    76. 28-76 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 Candidiasis Yeast infections resulting from imbalance of normal flora

    77. 28-77 Human diseases caused by fungi Fig. 28.32

    78. 28-78 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

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