Viruses, Bacteria and Archea

Transcription

1 10th Edition b. Bacilli: Bacillus anthracis SEM 35,000X b: Gary Gaugler/Visuals Unlimited; Sylvia S. Mader Viruses, Bacteria and Archea RNA envelope RNA c. d. a: Dr. Hans Gelderblom/Visuals Unlimited; b: Eye of Science/Photo Researchers, Inc. c: Dr. O. Bradfute/Peter Arnold, Inc.; d: K.G. Murti/Visuals Unlimited Structure Classification Reproduction Prokaryotes Influenza virus: RNA virus with a helical surrounded by an envelope with spikes. spikes Viruses 20 nm TEM 500,000X Tobacco mosaic virus: RNA virus with a helical. Outline BIOLOGY Chapter 20: pp Structure Reproduction Nutrition Bacteria Archaea 1 PowerPoint Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor Copyright The McGraw Hill Companies Inc. Permission required for reproduction or display 2 The Viruses Viral Diseases in Humans Are associated with a number of plant, animal, and human diseases Can only reproduce using the metabolic machinery of the host cell Are noncellular; May have a DNA or RNA genome. With the invention of the electron microscope, these infectious agents could be seen. 3 4

2 The Viruses: Structure The Viruses: Structure Generally smaller than 200 nm in diameter Each type has at least two parts Capsid: Outer layer composed of protein subunits Capsid (protein) Covering Some enveloped by membrane Others naked Envelope (not found in all viruses) Virus particle Nucleic acid molecule (DNA or RNA) Nucleic acid core: DNA or RNA Inner core Vary in shape from thread-like to polyhedral Various proteins (enzymes) 5 Viruses 6 Viral Categorization Classification is based on: Type of nucleic acid Size and shape Presence / absence of outer envelope Adenovirus: DNA virus with a polyhedral and a fiber at each corner. TEM 80,000X T-even bacteriophage: DNA virus with a polyhedral head and a helical tail. fiber protein TEM 90,000X fiber DNA protein unit neck tail sheath DNA tail fiber a. pins b. base plate 20 nm TEM 500,000X Tobacco mosaic virus: RNA virus with a helical. Influenza virus: RNA virus with a helical surrounded by an envelope with spikes. spikes RNA envelope RNA c. d. a: Dr. Hans Gelderblom/Visuals Unlimited; b: Eye of Science/Photo Researchers, Inc. c: Dr. O. Bradfute/Peter Arnold, Inc.; d: K.G. Murti/Visuals Unlimited 7 9

3 Parasitic Nature Viruses are: Obligate intracellular parasites Cannot reproduce outside a living cell Can be cultured only inside living cells Chicken egg Tissue culture Growing Viruses Ed Degginger/Color Pic Inc Viral Reproduction Gain entry into specific host cell Capsid (or spikes of the envelope) adhere to specific receptor sites on the host cell surface. Viral nucleic acid then enters a cell Viral genome codes for production of protein units in the. Relies on host cell enzymes, ribosomes, transfer RNA (trna), and ATP for its own replication The Bacteriophages: Reproduction Bacteriophages Viruses that infect bacterial cells Portions of adhere to specific receptor on the host cell Viral nucleic acid enters the cell Once inside, the virus takes over metabolic machinery of the host cell 12 17

4 Bacteriophages: The Lytic Cycle The Bacteriophages: The Lysogenic Cycle Lytic cycle may be divided into five stages: Attachment Penetration Biosynthesis Maturation Release Phage becomes a prophage Becomes integrated into the host genome Becomes latent May later reenter the lytic cycle 19 Lytic and Lysogenic Cycles in Prokaryotes Health Focus: Flu Viruses 1. ATTACHMENT Capsid combines with receptor. bacterial cell wall 20 nucleic acid bacterial DNA A flu virus has an H (hemagglutinin) spike and an N (neuraminidase) spike H spike allows the virus to bind to the receptor 2. PENETRATION Viral DNA enters host. 5. RELEASE New viruses leave host cell. INTEGRATION Viral DNA is integrated into bacterial DNA and then is passed on when bacteria reproduce. LYTIC CYCLE LYSOGENIC CYCLE 4. MATURATION Assembly of viral components. N spike attacks host plasma membranes viral DNA viral DNA 3. BIOSYNTHESIS Viral components are synthesized. prophage 16 different types Allows mature viruses to exit the cell 9 different types Each type of spike can occur in different varieties called subtypes. Our immune system only recognizes H spikes and N spikes it has been exposed to. daughter cells 21 23

5 Spikes of Bird Flu Virus Reproduction of Animal Viruses Animal virus enters the host cell Uncoating releases viral DNA or RNA RNA genome envelope N (neuraminidase) spike mutation 1 mutation 2 Budding: H (hemagglutinin) spike a. Viral genetic mutations occur in a bird host Viral particles released in a bud Acquires a membranous envelope Retroviruses (AIDS) Contain reverse transcriptase Carries out RNA " cdna reverse transcription cdna becomes integrated into host DNA Bird Flu virus Human flu virus combination In host cell b. Combination of viral genes occurs in human host Replicated as host DNA replicates Viral DNA is transcribed; new viruses are produced 24 Reproduction of the Retrovirus HIV-1 Viral Infections 1. Attachment receptor envelope spike 25 Viruses are best known for causing infectious diseases in plants and animals 2. Entry nuclear pore viral RNA reverse transcriptase cdna Integration Herpes, HIV, cancer 3. Reverse transcription Viroids host DNA ribosome viral mrna provirus 4. Biosynthesis ER viral enzyme protein 5. Maturation Viruses lack metabolism; thus, antibiotics have no effect Prions viral RNA Naked strands of RNA Many crop diseases Protein molecules with contagious tertiary structure Some human and other animal diseases - Mad cow disease 6. Release 28 31

6 The Prokaryotes Pasteur s Experiment Include bacteria and archaea, which are fully functioning cells A single spoonful of earth can contain >1000 prokaryotes Range in size from 1-10 m in length and m in width FIRST EXPERIMENT boiling to sterilize broth flasks outside building opened briefly HYPOTHESIS A: Bacteria arise spontaneously in a broth. HYPOTHESIS B: Bacteria in the air contaminate a broth. 89% show growth SECOND EXPERIMENT boiling to sterilize broth flask is open to air air here is pure air enters here flasks inside building opened briefly boiling to sterilize broth 32% show growth 100% have no growth bacteria collect here CONCLUSION: Hypothesis B is supported because relative concentrations of bacteria in the air explain the results. CONCLUSION: Hypothesis B is supported because when air reaching the broth contains no bacteria, the flask remains free of growth Prokaryote Structure Lack a membrane-bounded nucleus (DNA in nucleoid region) Outer cell wall containing peptidoglycan Some move by means of flagella Lack membranous organelles May have accessory ring of DNA (plasmid) Prokaryote Structure Prokaryotic cell Cell envelope Cytoplasm Appendages Glycocalyx Cell wall Plasma membrane Nucleoid Ribosomes Thylakoids (cyanobacteria) Flagella Conjugation pilus Fimbriae 37 39

7 Flagella Reproduction in Prokaryotes Asexual Prokaryotes reproduce asexually by means of binary fission Methods of genetic recombination Conjugation Sex pilus forms between two cells Donor cell passes DNA to recipient cell through pilus TEM 13,250X hook filament Transformation Transduction capsule cell wall basal body plasma membrane RDF/Visuals Unlimited 40 Fimbriae and Sex Pilus 41 Binary Fission epithelial cell of intestinal villus cytoplasm bacterium a. bacterium with fimbriae cell wall flagellum conjugation pilus fimbriae 5 m nucleoid 0.5 m b. 1 m CNRI/SPL/Photo Researchers, Inc. a: Courtesy USDA, photo by Harley W. Moon; b: Courtesy C. Brinton, Jr

8 The Endospore of Clostridium tetani Reproduction in Prokaryotes Transformation Occurs when bacterium picks up free pieces of DNA from other prokaryotes Becomes incorporated into genome endospore Transduction Occurs when bacteriophages carry portions of bacterial DNA from one cell to another Serve as vectors Some bacteria form resistant endospores under unfavorable conditions Alfred Pasieka/SPL/Photo Researchers, Inc. 48 Prokaryotic Nutrition 53 Autotrophic Prokaryotes Oxygen requirements: Obligate aerobes unable to grow in the absence of free oxygen Obligate anaerobes unable to grow in the presence of free oxygen Facultative anaerobes able to grow in either the presence or absence of free oxygen Photoautotrophs Use solar energy to reduce carbon dioxide to organic compounds Photosynthetic Chemoautotrophs Oxidize inorganic compounds to obtain the necessary energy Use it to reduce CO2 to an organic compound 56 Chemosynthetic 57

9 Nodules of a Legume Heterotrophic Prokaryotes Most prokaryotes are chemoheterotrophs that take in organic nutrients root Aerobic saprotrophs decompose most large organic molecules to smaller molecules Essential components of healthy ecosystem nodule May be free-living or symbiotic Nitrogen fixation Commensalism Parasites Courtesy Nitragin Company, Inc. 59 The Bacteria The Bacteria Bacteria are the more common type of prokaryote. Bacteria are commonly diagnosed using the Gram stain procedure When washed after staining: Over 2,000 different bacteria have been named. Gram-positive bacteria retain dye and appear purple Gram-negative bacteria do not retain dye and appear pink Most bacterial cells are protected by a cell wall 60 Contains peptidoglycan 61 64

10 The Bacteria Structure of cell wall also of diagnostic use Bacteria can be further classified in terms of their three basic shapes Spiral (spirilli), Rod (bacilli), and Round (cocci) Diversity of Bacteria a. Spirillum: SEM 3,520X b. Bacilli: SEM 35,000X c. Cocci: SEM 6,250X Spirillum volutans Bacillus anthracis Streptococcus thermophilus a: Dr. Richard Kessel & Dr. Gene Shih/Visuals Unlimited; b: Gary Gaugler/Visuals Unlimited; c: SciMAT/Photo Researchers, Inc Bacterial Diseases in Humans Cyanobacteria Formerly called the Blue-Green algae (Cyanophyta) Cyanobacteria are Gram-negative bacteria that photosynthesize Believed to be responsible for introducing oxygen into the primitive atmosphere Lack visible means of locomotion Can live in extreme environments When commensals with fungi, form lichens 69 71

11 Diversity Among the Cyanobacteria The Archaea plasma membrane cell wall a. Gloeocapsa LM 250X b. Oscillatoria LM 100X c. Oscillatoria cell a: Michael Abbey/Photo Researchers, Inc.; b: Tom Adams/Visuals Unlimited DNA thylakoids storage granule Archaea were earlier considered bacteria Carl Woese discovered that the base sequence of their rrna differs from Bacteria Other differences: Archaea do not have peptidoglycan in their cell walls like the Bacteria Archaea biochemical more like Eukarya than Bacteria Archaea now thought to be more closely related to Eukarya than to Bacteria Archaea Metabolism Types of Archaea Most are chemoautotrophs Some mutualistic Some commensalistic None known to be parasitic None are photosynthetic Many live in harsh conditions Many live in harsh conditions: Anaerobic marshes Methanogens Produce methane from hydrogen gas and carbon dioxide Salty lakes Halophiles Require high salt concentrations for growth, and Hot sulfur springs Thermoacidophiles Reduce sulfides and survive best at temperatures above 80ºC Plasma membranes contain unusual lipids convey tolerance of high temperatures 75 76

12 Extreme Habitats Salt Lake Extreme Habitats Hot Spring a(main): John Sohlden/Visuals Unlimited; a (Inset): From J.T. Staley, et al., Bergey's Manual of Systematic Bacteriology, Vol Williams & Wilkins Co., Baltimore. Prepared by A.L. Usted. Photography by Dept. of Biophysics, Norwegian Institute of Technology b(main): Jeff Lepore/Photo Researchers, Inc.; b (Inset): Courtesy Dennis W. Grogan, Univ. of Cincinnati; c(main): Susan Rosenthal/Corbis RM; c (Inset): Ralph Robinson/Visuals Unlimited Extreme Habitats Swamp Review Viruses Structure Classification Reproduction Prokaryotes Structure Reproduction Nutrition Bacteria Archaea c(main): Susan Rosenthal/Corbis RM; c (Inset): Ralph Robinson/Visuals Unlimited

13 BIOLOGY Chapter 20: pp th Edition b. Bacilli: Bacillus anthracis SEM 35,000X b: Gary Gaugler/Visuals Unlimited; 20 nm TEM 500,000X Tobacco mosaic virus: RNA virus with a helical. Sylvia S. Mader Viruses, Bacteria and Archea Influenza virus: RNA virus with a helical surrounded by an envelope with spikes. spikes RNA envelope RNA c. d. a: Dr. Hans Gelderblom/Visuals Unlimited; b: Eye of Science/Photo Researchers, Inc. c: Dr. O. Bradfute/Peter Arnold, Inc.; d: K.G. Murti/Visuals Unlimited PowerPoint Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor Copyright The McGraw Hill Companies Inc. Permission required for reproduction or display 81