Ch. 19 Viruses & Bacteria: What Is a Virus?

Ch. 19 Viruses & Bacteria: What Is a Virus? Define virus. What are viruses? Define and translate bacteriophage. Review virus composition. What two classes of compounds are found in all viruses? Define capsid. Identify the capsid in this diagram. What are the two primary functions of the capsid? Describe the viral MO in three words. Generally, how do different viruses compare in size and structure? 1

T4 Bacteriophage Head DNA Tobacco Mosaic Virus RNA How are viruses classified? Influenza Virus RNA Capsid Tail sheath Membrane envelope Tail fiber Capsid proteins Surface Glycoproteins Note the variety of nucleic acid, size, shape, complexity and accessories! What is the first level of viral classification? Define host range. Identify the host range of each example. How widely does host range vary? What is the second level of viral classification? Identify the GM of each example. What is the third level of viral classification? What is the forth level of viral classification? Define retrovirus. What is the source of the membrane envelope? Function of surface glycoproteins? 2

Viral Infection Describe how viruses trick the cell into allowing it inside? In general, what happens once the viral GM is inside? Specifically, what two possible modes or pathways may infection take? What does this depend on? Compare & contrast lytic vs. lysogenic infection? What is the most important difference between them? Define virulent virus. Which mode of infection do virulent viruses use? Define temperate virus. Define prophage. Which mode of infection do temperate viruses use? Define latent period. What triggers a prophage to leave the host chromosome and be expressed? 3

HIV Study the diagram showing the mode of HIV infection. Identify this cell. What is this cell's general function? What is HIV's classification? Explain what designates HIV as a retrovirus. Is HIV virulent or temperate? How do you know? What is the latent period of the HIV provirus without treatment? Refer to the diagram to describe each step of HIV infection. When, in relation to cells, did viruses probably appear on Earth? Explain why. Where did they come from or from what did they develop? Do viruses spontaneously generate today? Where do new viruses come from? Do viruses evolve? How do you know? Which viruses evolve most quickly and why? 4

Pandemic Viral Disease in Humans Does viral infection always produce disease? How do viruses cause disease? (HIV, zika) Can antibiotics be used to treat viral infection? Why? What are used to prevent viral infection? How do vaccines work? What's the drawback? Can anything be used to prevent viral disease following infection? What's the drawback? What is the difference between an epidemic and a pandemic? What is one virus/disease that the World Health Organization wiped off the face of the Earth (almost)? How did they do it? Why can't we do the same for all viruses? 5

Viral Diseases Study the table... Identify the diseases for which there are vaccines. What determines which viruses we are able to develop vaccines for? Why? Other than human disease, how else do viruses affect us? (ssrna) (ssrna) (ssrna) (dsdna) Ebola: Nausea, vomiting, diarrhea (may be bloody), red eyes, raised rash, chest pain and cough, stomach pain, severe weight loss, bleeding, usually from the eyes, and bruising (people near death may bleed from other orifices, such as ears, nose and rectum) (dsdna) (ssrna) Zika (ssrna) Ebola (ssrna) Fever, rash, joint pain, red eyes, microcephaly in newborns Hemorrhagic fever (see left) 6

Viroids Viroids are bare single-strand RNA loops of around 300 nucleotides. They do not code for protein. The simplest of infectious agents, viroids may be similar to the first virus-like particles and remnants from the RNA world. Potato Spindle Tuber Disease (elongated & misshapen potatoes) Compare & contrast viroid and virus structure. Identify the general host range of viroids. How do viroids usually enter their host? Why? What effect do they have on their host? Study the experiment diagram... Identify the compounds that end in ase. What is in each test tube along with the enzyme? What is the purpose of no treatment? What does each enzyme do in this experiment? (Same as the Avery experiment.) What do blotches on the leaves represent? What do these results suggest? 7

Prions Compare & contrast virus, viroid & prion structure. Identify the general prion host range. How is prion disease transmitted? Why? What effect do they have on their host? Study the diagram... Identify and describe initial prion formation. Describe recruitment. Describe the formation of amyloid plaques. Define & determine the effect of fractionation. Identify two diseases caused by prions. At this time, what is the only absolute diagnosis? Study the photo... Identify the normal brain vs. the prion infected brain. 8

Bacteria Which prokaryotic Domain and Kingdom are represented in the photo? How do you know? Review the type of cell bacteria are. Review the size bacteria are relative to eukaryotic cells. How common and abundant are bacteria relative to other organisms? How were all prokaryotes once classified? Identify the two prokaryotic Domains. Identify the two prokaryotic Kingdoms. Determine and describe the importance of bacteria in the biosphere. 9

Classifying Prokaryotes: Eubacteria Ribosomes Cell Wall Plasma Membrane Peptidoglycan Flagellum Pili DNA Identify the Domain, Kingdom and species this diagram represents. Review and add the functions of each structure labeled in the diagram. Use a bracket to label the nucleoid region. How is this different than a nucleus? Label the cytoplasm. What is it? Do all cells have it? Why? Draw in and label at least one plasmid. What is it and how does it function? What is labeled Cell Wall actually includes an Outer Membrane. Label it! Do all bacteria have an outer membrane? What is it made of? What is its significance? Draw a thicker layer outside the outer membrane and label it Capsule. Do all bacteria have a capsule? What is it made of? What is its significance? How do Eubacteria compare to Archaebacteria in terms of diversity and habitat? 10

Classifying Prokaryotes: Archaebacteria How do Archaebacteria generally compare to Eubacteria in their outward appearance? How can we tell them apart? What is different about Archaea cell walls? What is different about Archaea plasma membranes? Bacteria What is different about Archaea genes? With which Domain are their genes similar? What does this suggest? Why do they have these differences? What are Methanogens and where do they live? What are Halophiles and where do they live? What are Thermophiles and where do they live? Eukarya Archaea 11

Identifying Prokaryotes: Eubacteria What is needed to see prokaryotes? Is it easy to identify different species visually? Why? What characteristics do microbiologists use to identify different species or strains? Identify and label the three major shapes shown in these micrographs. How can looking at living Eubacteria using a light microscope help distinguish them?. What can be altered or measured in cell culture to distinguish them? Identify and label the procedure shown in the diagram. What does it determine? What is the difference between Gram + and Gram bacteria? Explain how this information would be useful to doctors attempting to cure a bacterial infection? Which is the most effective means of distinguishing bacterial species or strains?... 12

Identifying Prokaryotes: Metabolic Diversity Cyanobacteria Deep Oceanic Vent Tube Worm Bacteria Mycobacterium tuberculosis Identify the two general requirements to sustain life. Define metabolism. Identify and define the two matter handling modes of prokaryote metabolism. Are these designations strictly prokaryotic? How do you know? Identify and define the two energy handling modes of prokaryote metabolism. Combine, list and define the 4 modes of metabolism that represent prokaryote diversity. Match each example above with one of the four combined modes. In general, describe the level of prokaryote metabolic diversity and infer why this is so. Identify your own mode of metabolism! Plantae? Fungi? Protista? Identify the two processes prokaryotes utilize to break down food molecules and convert energy for cellular work... 13

Identifying Prokaryotes: Metabolic Diversity Define aerobic cellular respiration. Define aerobic. Define anaerobic fermentation. Define anaerobic. Define obligate. Define facultative. Study the diagram Identify the representation of test tubes, liquid culture medium, the air-medium interface, bacterial cells, and the oxygen concentration gradient. [O2]g Are these the same species or strains of bacteria? How do you know? Explain the distribution of bacteria in each culture. Identify and label each culture combining the terms you defined. Bacteria in liquid cultures. 14

Prokaryote Growth and Reproduction Identify the general process taking place in this micrograph. Which type of reproduction is this? Describe in your own words how this happens. Define and describe prokaryotic binary fission. At this point, it is still one cell. What is it called? What are the two cells resulting from the split called? How will the two daughter cells compare to each other and the parent cell? Will the parent cell still exist? Will the daughter cells grow? What is the advantage of this type of reproduction? Disadvantage? What are two ways this disadvantage is overcome?... 15

Prokaryote Genetic Recombination Identify the general process taking place in this micrograph. Is this a form of reproduction? How do you know? What is the observable difference between these cells? Describe in your own words what is happening. Define and describe prokaryotic conjugation. In which direction is the transfer? What part of the genome is transferred? What kind of genetic information may be transferred? How will the two cells compare afterward? Review bacterial transformation. Define bacterial transduction. What is the advantage of these processes for prokaryotes? What is the advantage of these processes for humans? Disadvantage for humans and other species? 16

Prokaryote Survival & Dispersal Identify and label the endospores in these micrographs. What do they contain? What surrounds them? When do they form? What happens to the rest of the cell? Define dormant? How long can they remain dormant? When do they return to activity? Explain the primary purpose of endospores. Explain a secondary purpose. 17

Importance of Bacteria Identify and explain four ecological roles for bacteria in the biosphere? Draw and label these roles on this food web diagram. 18

Importance of Bacteria in the Nitrogen Cycle Rhizobium nodules on a legume. To which organisms is nitrogen important? Why? (Review) What percentage of Earth's atmosphere is nitrogen? Study the diagram... Identify the only organisms able to incorporate atmospheric N2. Define nitrogen fixation. Define legume. Identify the relationship this is an example of. Identify the other general role bacteria play in the cycle. Explain the general importance of nitrogen fixing and nitrifying bacteria. 19

Importance of Bacteria to Humans Use the images on this slide to identify and list additional ways prokaryotes are important to us. Breyers Light Probiotics Plus Yogurt contains an added dose of live, active Bifidobacterium yogurt culture. 20

Prokaryotic Diversity 19-3 Diseases Caused by Bacteria and Viruses Bacterial pathogens Of the 20 bacterial phyla currently recognized, thirteen are not present in this figure due to the absence of noteworthy pathogens. Some of these missing phyla are relatively important, like the Cyanobacteria. Study the diagram while reading the caption. Identify this type of diagram. Generally, what does it show? Generally, where can you find bacteria and viruses in nature? Reletively, how many cause disease? Define pathogen. In general, how do pathogenic bacteria cause disease?... 21

Study the diseases and symptoms in this table... Identify, list and explain two ways bacteria produce these symptoms. Define bacterial exotoxin. Define bacterial endotoxin. Bacterial Diseases 22

Bacterial Disease in Humans Study the diagram while reading the caption. Are there vaccines that protect against bacterial pathogens? Define vaccine. Explain how vaccines work. Define immunity. Identify the component of the immune system responsible for imparting immunity. A vaccine is made from an antigen isolated or produced from the disease-causing microorganism. The vaccine is injected into the blood stream. Macrophages patrolling tissues recruit Killer T-cells which go to work to remove the threat. B-cells in the blood stream, with the help of helper T-cells, respond to the antigen by producing antibodies. The antibodies bind to the antigen to "neutralize"or inactivate it. In addition, memory cells are produced and remain ready to mount a quick protective immune response against subsequent infection with the same disease causing agent. 23

Determining Antibiotic Sensitivity Effects of different antibiotics on growth of a Bacillus strain. The right-hand image shows a close-up of the novobiocin disk (marked by an arrow on the whole plate). In this case some individual mutant cells in the bacterial population were resistant to the antibiotic and have given rise to small colonies within the zone of inhibition. Study the diagram while reading the caption. Define antibiotic. Which disk in the sensitivity screening is the control? What is likely on it? Define antibiotic resistance. Review how bacteria may become resistant. Define antibiotic sensitivity. Define zone of inhibition. When is it most likely a bacterial population will be sensitive to a particular antibiotic? 24 Based on these results, which antibiotics should be used? How do you know?

Controlling Bacteria A hamburger patty cooked to 160 F, regardless of color, is safe. Use the images on this slide to identify and list ways prokaryotes can be controlled. Include the effect each method has on bacteria. 25