BSC 160 1st Edition Exam 2 Study Guide Lectures 13 23 Lecture 13 Chapter 13 Basic Virology A virus for every organism most abundant microbe Because viruses attack every domain prokaryotes eukaryotes viruses play big role in evolution of domains Problems being a virus Timing is everything Replicating so fast that you kill your host before spreading progeny Very narrow host range Virus is dependent on certain proteins in host If too narrow virus can be eradicated Mutations More genes you have easier for host to attack you Viruses have to coordinate reproductive cycle right proteins made at right times for assembly Properties of Viruses Obligate intracellular parasites do harm to host inside cell Microscopic in size Acellular not made up of cells Compact structure Do not independently fulfill characteristics of life Inactive macromolecules outside host cell active only inside host cell Basic structure Protein shell capsid surrounding nucleic acid core Nucleic acid can be either DNA or RNA not both Nucleic acid can be double stranded DNA single stranded DNA s strand RNA or dub strand RNA Molecules on virus surface impart high specificity for attachment to host cell Ability to take over the host cell s transcription translation enzymes Lack enzymes for most metabolic processes Lack machinery for synthesizing proteins Capsid Protein coat which protects nucleic acid can be multiple proteins or copies of single protein Protects from temperature environment Also plays role in delivery Nucleocapsid Nucleic acid capsid Enveloped Host cell plasma membrane wrapped around them Plyomorphic Peplomer Attachment Rod circle off membrane Naked viruses do not have envelopes just have capsid Primary Structures of Viruses 1 2 Proteins that make up acid are capsomers Icosohedral Simple Soccer ball shape nucleic acid inside 20 sided equilateral trianges Constrained Only certain size Example Adenovirus Helical cylindrical wrapped around nucleic acid Phage Virus that infects bacteria Enveloped Viruses that attacks animals Complex Viruses Atypical Genome Can be DNA or RNA Single or double stranded Each virus will contain only one type Nuclear Proteins Present inside capsid with nucleic acid Functions Viral maturation entrance into new host DNA RNA Replicases Reverse transcriptase Viruses are not motile Random collision Move by heat of system until bump into appropriate host Life Cycle of a Virus Attachment Adsorption Bind to molecule on host to gain entry Early Phase Entry Penetrate Whole capsid doesn t have to enter cell o Have to uncoat Lecture 14 Entry of Animal Viruses into Host Cells Endocytosis of naked virus Animation Attachment Early Phase Entry Nucleic acid is now inside decision point with viruses Become lytic or lysogenic Release of progeny if Host health good Host decides to be Lytic Rapid growth rupture in host cell Lysis Lysogenic Silent viral infection viral genome is incorporated into host genome when divides each daughter cell has virus Bacterial phague attack bacteria alternate between these states Lysogenic creates temperant phague Prophase virus to be Can be induced and become lytic again Human lysogenic virus Herpes Shingles NEXT Virus is in Lysogenic or Lytic decided Replication to Synthesis Early genes Lysogenic decision takes over gene expression of host Middle genes DNA RNA polymerase viral genome replication late gene expression Late genes Capsid scaffolding proteins cell lysis Late phase Translation of proteins Assemble viruses Release of virus Animations 13 8 13 9 13 10 in Etextbook Virology Challenge to study virus getting sick multiple viruses in different versions Viruses are obligate intracellular parasites need host studying animals is a last resort Medical Importance of Viruses Viruses are the most common cause of acute infections Possible connections between viruses chronic afflictions of unknown cause Viruses are major participants in earth s ecosystem Detection Treatment of Animal Viral Infections More difficult than other agents Consider overall clinical picture take appropriate sample Infect cell culture look for characteristic cytopathic effects Screen for parts of virus Screen for immune response to virus antibodies Antiviral drugs can cause serious side effects To kill a virus we have to attack our own cells Microbial Nutrition Process by which we acquire nutrition from environment Energy Macronutrients Need to make up bioelements Carbon Oxygen Nitrogen Hydrogen Phosphorus Micronutrients Sulfure Potassium Magnesium Calcium Iron Needed for cellular processes Trace elements Cobalt zinc Molybdenum Copper Manganesse Nickle Cofactors Growth Factors have to be taken up by environment Can t be synthesized Vitamins enzymes Lecture 15 Growth factor things organisms cannot synthesize Have to come from environment Ex Vitamins amino acids nucleic acids How does environment impact nutrition for a microbe Growth factor tells about organism s metabolic synthesis Also tells about environment whether it is specific to microbe growth or not Nutritional Classification Carbono Autotroph from CO2 Not nutritionally dependent on any other organisms o Heterotroph Reduced Carbon source get C in organic form from another organism Energy Sourceo Phototrophs from sunlight o Chemotrophs Oxidized in organic compounds as energy source Primary determinants for classification Hydrogen or electron source o Lithotrophs Reduce inorganic molecules o Organotrophs Reduce organic molecules Nutritional Classification Table 5 4 There are nutrient needs beyond Hydrogen Carbon electrons What percent of microbes can we grow 2 Ones that are relevant 10 Need appropriate media to grow Minimal media synthetic chemically defined Represents minimal nutrients for organism to grow Complex Rich media Not chemically defined Don t know everything in it Selective Growth of some organisms and not others bc they can t grow in that environment Differential Some specific chemical agent allows microorganisms to grow but show something different about them Ex Color morphology changes in colony morphology Both Selective differential Promotes growth of one type of microbe shows differences Concky Fermented changes acids Change in color Sterilization Microbial Growth Growth of microbe is influencing factor of microbe environment on global scale Quantifying Bacterial Growth Growth Divide Increase of number in bacterial cells Binary Fission 6 1 6 3 in text WATCH Process from going from a parental cell to 2 identical daughter cells