BSC 160 1st EditionExam # 2 Study Guide Lectures: 13 - 23Lecture 13Chapter 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 domainsProblems 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 assemblyProperties 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-strandRNA- 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 proteinsCapsid- Protein coat which protects nucleic acid; can be multiple proteins or copies of single protein- Protects from temperature, environmentAlso plays role in delivery- Nucleocapsid= Nucleic acid + capsidEnveloped- Host cell plasma membrane wrapped around them. Plyomorphic.- Peplomer- Attachment; Rod & circle off membrane. Naked viruses do not have envelopes, just have capsidPrimary Structures of Viruses- Proteins that make up acid are capsomers 1. Icosohedral- Simple. Soccer ball shape, nucleic acid inside- 20 sided, equilateral trianges- Constrained. Only certain size- Example: Adenovirus2. Helical- cylindrical, wrapped around nucleic acid- Phage- Virus that infects bacteriaEnveloped Viruses- that attacks animalsComplex Viruses- Atypical. Genome- Can be DNA or RNA- Single or double stranded- Each virus will contain only one typeNuclear Proteins- Present inside capsid with nucleic acidFunctions: Viral maturation & entrance into new host: DNA/RNA/Replicases/Reverse transcriptaseViruses 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 cello Have to uncoat Lecture 14Entry of Animal Viruses into Host Cells- Endocytosis of naked virus AnimationAttachment: 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 virusBacterial 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 SynthesisEarly genes: Lysogenic decision, takes over gene expression of hostMiddle genes: DNA/RNA polymerase viral genome replication late gene expressionLate genes: Capsid scaffolding proteins cell lysisLate phase: Translation of proteins, Assemble viruses, Release of virus Animations: 13.8, 13.9, 13.10 in EtextbookVirology- Challenge to study virus: getting sick, multiple viruses in different versions, Viruses areobligate intracellular parasitesneed host , studying animals is a last resortMedical Importance of VirusesViruses are the most common cause of acute infections- Possible connections between viruses & chronic afflictions of unknown cause- Viruses are major participants in earth’s ecosystemDetection & 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 effectsTo kill a virus, we have to attack our own cellsMicrobial Nutrition- Process by which we acquire nutrition from environment  EnergyMacronutrients= Need to make up bioelements: Carbon, Oxygen, Nitrogen, Hydrogen + PhosphorusMicronutrients= Sulfure, Potassium, Magnesium, Calcium, Iron. Needed for cellular processesTrace elements= Cobalt, zinc, Molybdenum, Copper, Manganesse, Nickle . CofactorsGrowth Factors= have to be taken up by environment. Can’t be synthesized- Vitamins, enzymesLecture 15Growth factor- things organisms cannot synthesize. Have to come from environment.Ex.) Vitamins, amino acids, nucleic acidsHow 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 notNutritional Classification- Carbon- o Autotroph (from CO2): Not nutritionally dependent on any other organismso Heterotroph: Reduced Carbon source (get C in organic form from another organism)- Energy Source- o Phototrophs (from sunlight)o Chemotrophs: Oxidized in/organic compounds as energy source^^^Primary determinants for classification^^^- Hydrogen or electron source: o Lithotrophs: Reduce inorganic moleculeso Organotrophs: Reduce organic moleculesNutritional Classification—Table 5.4There 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,