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BIOLOGY Chapter 20: pp. 354 - 372 10th Edition Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 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 capsid. Sylvia S. Mader Viruses, Bacteria and Archaea Influenza virus: RNA virus with a helical capsid surrounded by an envelope with spikes. spikes RNA capsid envelope RNA c. capsid 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 1 Outline Viruses Structure Classification Reproduction Prokaryotes Structure Reproduction Nutrition Bacteria Archaea 2 The Viruses 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 The Viruses: Structure Generally smaller than 200 nm in diameter Each type has at least two parts Capsid: Outer layer composed of protein subunits Some enveloped by membrane Others “naked” Nucleic acid core: DNA or RNA Vary in shape from thread-like to polyhedral 4 The Viruses: Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Capsid (protein) Covering Envelope (not found in all viruses) Virus particle Nucleic acid molecule (DNA or RNA) Inner core Various proteins (enzymes) 5 Viruses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Adenovirus: DNA virus with a polyhedral capsid and a fiber at each corner. TEM 80,000X TEM 90,000X T-even bacteriophage: DNA virus with a polyhedral head and a helical tail. fiber protein capsid fiber DNA protein unit neck tail sheath DNA capsid tail fiber pins a. base plate b. 20 nm TEM 500,000X Tobacco mosaic virus: RNA virus with a helical capsid. Influenza virus: RNA virus with a helical capsid surrounded by an envelope with spikes. spikes RNA capsid envelope RNA c. capsid 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 6 Viral Categorization Classification is based on: Type of nucleic acid Size and shape Presence / absence of outer envelope 7 Parasitic Nature Viruses are: Obligate intracellular parasites Cannot reproduce outside a living cell Can be cultured only inside living cells Chicken egg Tissue culture 8 “Growing” Viruses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Ed Degginger/Color Pic Inc. 9 Viral Reproduction Gain entry into specific host cell Viral nucleic acid then enters a cell Capsid (or spikes of the envelope) adhere to specific receptor sites on the host cell surface. Viral genome codes for production of protein units in the capsid. Relies on host cell enzymes, ribosomes, transfer RNA (tRNA), and ATP for its own replication 10 The Bacteriophages: Reproduction Bacteriophages – Viruses that infect bacterial cells Portions of capsid 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 11 Bacteriophages: The Lytic Cycle Lytic cycle may be divided into five stages: Attachment Penetration Biosynthesis Maturation Release 12 The Bacteriophages: The Lysogenic Cycle Phage becomes a prophage Becomes integrated into the host genome Becomes latent May later reenter the lytic cycle 13 Lytic and Lysogenic Cycles in Prokaryotes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. ATTACHMENT Capsid combines with receptor. bacterial cell wall nucleic acid bacterial DNA capsid 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 viral DNA viral DNA LYSOGENIC CYCLE 4. MATURATION Assembly of viral components. 3. BIOSYNTHESIS Viral components are synthesized. prophage daughter cells 14 Health Focus: Flu Viruses A flu virus has an H (hemagglutinin) spike and an N (neuraminidase) spike H spike allows the virus to bind to the receptor N spike attacks host plasma membranes 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. 15 Spikes of Bird Flu Virus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. capsid RNA genome envelope N (neuraminidase) spike H (hemagglutinin) spike mutation 1 mutation 2 a. Viral genetic mutations occur in a bird host Human flu virus Bird Flu virus combination In host cell b. Combination of viral genes occurs in human host 16 Reproduction of Animal Viruses Animal virus enters the host cell Uncoating releases viral DNA or RNA Budding: 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 Replicated as host DNA replicates Viral DNA is transcribed; new viruses are produced 17 Reproduction of the Retrovirus HIV-1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. Attachment receptor envelope spike 2. Entry capsid nuclear pore 3. Reverse transcription viral RNA reverse transcriptase cDNA Integration host DNA ribosome 4. Biosynthesis ER viral mRNA provirus viral enzyme capsid protein 5. Maturation viral RNA 6. Release 18 Viral Infections Viruses are best known for causing infectious diseases in plants and animals Herpes, HIV, cancer Viroids Viruses lack metabolism; thus, antibiotics have no effect Naked strands of RNA Many crop diseases Prions Protein molecules with contagious tertiary structure Some human and other animal diseases - Mad cow disease 19 The Prokaryotes Include bacteria and archaea, which are fully functioning cells A single spoonful of earth can contain >1000 prokaryotes Range in size from 1-10 µm in length and 0.7-1.5 µm in width 20 Pasteur’s Experiment Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. HYPOTHESIS A: Bacteria arise spontaneously in a broth. HYPOTHESIS B: Bacteria in the air contaminate a broth. FIRST EXPERIMENT SECOND EXPERIMENT flask is open to air flasks outside building opened briefly boiling to sterilize broth 89% show growth boiling to sterilize broth air here is pure air enters here flasks inside building opened briefly boiling to sterilize broth bacteria collect here 32% show growth CONCLUSION: Hypothesis B is supported because relative concentrations of bacteria in the air explain the results. 100% have no growth CONCLUSION: Hypothesis B is supported because when air reaching the broth contains no bacteria, the flask remains free of growth. 21 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) 22 Prokaryote Structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prokaryotic cell Cell envelope Glycocalyx Cell wall Plasma membrane Cytoplasm Nucleoid Ribosomes Thylakoids (cyanobacteria) Appendages Flagella Conjugation pilus Fimbriae 23 Flagella Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. TEM 13,250X hook filament capsule cell wall basal body plasma membrane © RDF/Visuals Unlimited 24 BACTERIA & VIRUSES Prokaryotic vs. Eukaryote Flagella Binary Fission Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. cytoplasm cell wall nucleoid 0.5 µm © CNRI/SPL/Photo Researchers, Inc. 26 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 Transformation… Transduction… 27 Fimbriae and Sex Pilus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. epithelial cell of intestinal villus bacterium a. bacterium with fimbriae flagellum conjugation pilus fimbriae b. 5 µm 1 µm a: Courtesy USDA, photo by Harley W. Moon; b: Courtesy C. Brinton, Jr. 28 Reproduction in Prokaryotes Transformation Occurs when bacterium picks up free pieces of DNA from other prokaryotes Becomes incorporated into genome 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 29 BACTERIA & VIRUSES Spore Forming Bacteria: Endospores NOT a form of reproduction One endospore per cell Contain chromosome & small amount cytoplasm Allow germination after decades or centuries BACTERIA & VIRUSES B. subtilis B. anthracis The Endospore of Clostridium tetani Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. endospore © Alfred Pasieka/SPL/Photo Researchers, Inc. 32 Prokaryotic Nutrition 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 33 Autotrophic Prokaryotes 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 Chemosynthetic 34 Heterotrophic Prokaryotes Most prokaryotes are chemoheterotrophs that take in organic nutrients Aerobic saprotrophs decompose most large organic molecules to smaller molecules Essential components of healthy ecosystem May be free-living or symbiotic Nitrogen fixation Commensalism Parasites 35 Nodules of a Legume Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. root nodule Courtesy Nitragin Company, Inc. 36 The Bacteria Bacteria are the more common type of prokaryote. Over 2,000 different bacteria have been named. Most bacterial cells are protected by a cell wall Contains peptidoglycan 37 BACTERIA & VIRUSES Gram Pos. Cell Wall BACTERIA & VIRUSES Gram Neg. Cell Wall The Bacteria Bacteria are commonly diagnosed using the Gram stain procedure When washed after staining: Gram-positive bacteria retain dye and appear purple Gram-negative bacteria do not retain dye and appear pink 40 BACTERIA & VIRUSES GRAM STAIN BACTERIA & VIRUSES Gram + Cocci Gram - Bacilli The Bacteria Structure of cell wall also of diagnostic use Bacteria can be further classified in terms of their three basic shapes Spiral (spirilli), Spirochaete Rod (bacilli), and Round (cocci) Vibrio (comma) 43 BACTERIA & VIRUSES Diversity of Bacteria Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. Spirillum: Spirillum volutans SEM 3,520X b. Bacilli: Bacillus anthracis SEM 35,000X c. Cocci: SEM 6,250X Streptococcus thermophilus a: © Dr. Richard Kessel & Dr. Gene Shih/Visuals Unlimited; b: © Gary Gaugler/Visuals Unlimited; c: © SciMAT/Photo Researchers, Inc. 45 Animation Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 46 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 47 Diversity Among the Cyanobacteria Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. DNA thylakoids plasma membrane cell wall storage granule a. Gloeocapsa LM 250X b. Oscillatoria LM 100X c. Oscillatoria cell a: © Michael Abbey/Photo Researchers, Inc.; b: © Tom Adams/Visuals Unlimited 48 The Archaea 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 49 Archaea Metabolism Most are chemoautotrophs Some mutualistic Some commensalistic None known to be parasitic None are photosynthetic Many live in harsh conditions 50 Types of Archaea Many live in harsh conditions: Anaerobic marshes Salty lakes Methanogens Produce methane from hydrogen gas and carbon dioxide 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 51 Archaebacteria vs. Eubacteria •Cell Wall Eubacteria: Peptidoglycan Archaebacteria: No peptidoglycan •Plasma Membrane: Eubacteria: Lipids in bilayer “ester-linked’. Archaebacteria: “Ether-linked” 52 BACTERIA & VIRUSES Archaebacteria vs. Eubacteria •GENE TRANSFER MACHINERY: Eubacteria: Ribosomal proteins & RNA polymerase different from Eukaryotes. Archaebacteria: Ribosomal protein & RNA is SIMILAR to eukaryotes BACTERIA & VIRUSES Archaebacteria vs. Eubacteria •GENE ARCHITECTURE: Eubacteria: No Introns Archaebacteria: Sometimes Introns BACTERIA & VIRUSES PROKARYOTE VS. EUKARYOTE 1. Multicellularity 2. Cell Size 3. Chromosomes 4. Cell Division/Genetic Recombination A. Asexual Division: a. Binary Fission b. Fragmentation c. Budding BACTERIA & VIRUSES Bacterial Growth Curve BACTERIA & VIRUSES BACTERIAL GROWTH 1. Lag Phase: Intense synthesis of enzymes & AA Bacteria adjusting to new substrate 2. Log Phase: Exponential growth N(t) = N(0)2n 3. Stationary Phase: Equilibrium achieved death = replication BACTERIA & VIRUSES BACTERIAL GROWTH 3. Stationary Phase: Essential nutrient depleted Toxic byproducts Physiologic Change occurs Metabolism becomes unbalanced Gram staining variable Peptidoglycan cell wall deteriorates BACTERIA & VIRUSES BACTERIAL GROWTH 4. Death Phase: Death rate exceeds replication Bacteria decrease exponentially BACTERIA & VIRUSES MEASURING BACTERIAL GROWTH 1. Viable Counts: Each bacterium produces colony CFU’s 2. Turbidity: Spectrophotometry Higher population, less transmission 3. Analysis of Cellular Components Measure amount of DNA, Protein, etc. BACTERIA & VIRUSES Viable counts Utilize serial Dilutions. Count the CFU’s BACTERIA & VIRUSES MEASURING BACTERIAL GROWTH 1. Viable Counts: Each bacterium produces colony CFU’s 2. Turbidity: Spectrophotometry Higher population, less transmission 3. Analysis of Cellular Components Measure amount of DNA, Protein, etc. BACTERIA & VIRUSES Spectrophotometric analysis measures the turbidity of a solution BACTERIA & VIRUSES MEASURING BACTERIAL GROWTH 4. Analysis Metabolic Products: Measure consumption substrate Measure substance produced e.g. Lactic acid Bacterial Diseases in Humans 65 Viral Diseases in Humans 66