Biol 121 Lecture notes.pdf

Impact of Microbes (Lec 1) Microbiology: Study of organism which is too small to be seen by unaided eye Diseases: - Cause by pathogen - Controlled by combination of vaccination, antibodies, personal hygie...

Impact of Microbes (Lec 1) Microbiology: Study of organism which is too small to be seen by unaided eye Diseases: - Cause by pathogen - Controlled by combination of vaccination, antibodies, personal hygiene Impact of microorganism: Both beneficial & harmful to human ▪ e.g. Food (Beneficial) Microbiological activity (Harmful) Food spoilage & borne diseases Three domains: Eukaryote Bacteria Archaea - One or more cell [First life form appear & - Similar to bacteria in size - Has nucleus & well- habitat] and simplicity of structure developed intracellular - Different in molecular compartments - Large domain of organization prokaryotic microorganism Characteristics: - characteristic tRNAs & ribosomal RNA - X peptidoglycan cell wall, Has proteinaceous coat - Has ether linked lipids Cell volume: Higher SA/Vol ratio → nutrient exchange increases → growth and greater evolutionary  Impact of Microbes Cell membrane function: - Barrier function (Selectively permeable barrier) - Respiration/Photosynthesis - Energy conservation (Proton motive force) Cell wall: - Determine & Maintain the shape - Protects the cell from osmotic lysis Gram-positive cell wall Gram-negative cell wall - Outer membrane is harder to treat → More resistant - LPS: protective layer Gram stain: Positive [Blue/purple] Gram stain: Negative [pink/red] Capsule Fimbriae and Pili Protection from phagocytosis Fimbriae: Recognition and attachment Protection from harsh environmental conditions Pili: Mating Attach on surfaces Flagella: Locomotion - Rigid layer: - Hold by glycosidic bonds - MG linked via peptide bridge  Impact of Microbes Bacterial cytoplasm: Nucleoid Plasmid - Irregularly shaped region [Small, closed circular DNA molecules] - Exist and replicate independently of chromosome - X required for growth and reproduction - Carry genes → Selective advantage Cellular inclusions Endospores [Granules of material, reserved for future Advantages: use] - Survive for long term - Gas vesicles: Buoyancy in some aquatic → produced under unfavourable conditions bacteria (e.g. Cyanobacteria) - Highly resistant to extreme condition - Contain calcium dipicolinate (Binds free water and helps dehydrate cell) (Some contain iron → Orient cells in - Special protein that protects DNA magnetic fields)  Impact of Microbes Bacterial nutrition and growth (Lec 2) Nutrient: Provide element for synthesis of cell material Microelement/ Microelement/ Macronutrient Micronutrient Required amount Large Small Where All cell X required by all organism What C,O,H,N,P,S,K,C,Mg,Fe Cu,Zn,Ni,V,Se (Component of enzyme) Providing nutrient: - Culture media : All elements for growth - Chemically defined media: Exact chemical composition (Vitro cell culture) - Complex media: X know exact composition, digests of complex material Bacteria grow: - nutrient agar plate (Solid culture media) (For purification) - Liquid media (e.g. Erlenmeyer flasks, test tubes) Grow in batch culture (Closed system) (X nutrient added) 1. Lag phase 2. Log phase 3. Stationary phase 4. Death phase  Impact of Microbes Bacterial growth : increase cell no. Binary fission [Divide= 1 generation] → ideal population: exponential Bacterial growth: - Culture bacteria: in media - Viable cell: - Viable but non-culturable bacteria - X grow in conventional media Cell counting (By microscopy): - Total count: All stained bacteria - Viable count: Cells with activity (Fluorescent activity dye) - Culturable count: Form colonies (Solid) , Increase turbidity (Liquid) Measuring bacterial growth: Direct microscopic count Agar plate Culturable count = plate count = colony count Assumption: culturable cell will grow and divide to yield one colony Advantage: Easy & Fast Disadvantage: - specific microscope - X differentiate live or dead Serial dilution Turbidity (Light absorbance) Cloudy: cells scatter light passing through suspension  Impact of Microbes Metabolic classification of bacteria: - Carbon resources: 1) Heterotrophs 2) Autotrophs - Energy resources: 1) Phototrophs 2) Chemotrophs (Oxidisation happens) Environmental effect: Oxygen Temperature (Different bacteria have its optimal/living range) pH Osmolarity - Halophiles: Grow in habitats in high salt conc. - Mild: 1-6% -Moderate: 7-15% -Extreme: 15-30% High salt conc.: Lower water activity → Osmosis (Most alkaliphiles are halophilic)  Impact of Microbes How bacteria cause diseases (Lec 3) Most bacteria harmless: Host immune system prevent most bacteria Host: Organism support growth of viruses, bacteria & parasites Pathogen: Organism causes diseases by impairing or interfering with normal physiological activities of the host Pathogenicity: Ability to cause diseases Virulence: Degree/intensity of pathogenicity (Toxicity & Invasiveness) Infection vs diseases: Health → Infection → Diseases 1) Germ theory of diseases 2) Develop simple method of obtaining bacteria in simple culture Bacterial pathogens: o Opportunistic pathogens: Cause diseases when host defence are impaired o primary pathogens: Capable of causing diseases in absence of immune affect (Cause diseases to survive, human/animal-human transmission)  Impact of Microbes Steps in infectious diseases 1. Reservoirs: Where bacterial pathogen live & large amount of reproduce (e.g. human, animal, environment) 2. Transfer to host: - direct host-host transmission (Airborne, body contact) - Indirect host-host transmission (Vectors-borne transmission, vehicles) 3.1. Colonisation: Establishment of stable population of bacteria in the host - Need to compete nutrients & surface attachment sites 3.2. Adherence: Overcome flushing mechanisms (Adhere on host surface) 1. Association: involve non-specific forces (charge & hydrophobicity) 2. Adhesion: Involve adhesins and host receptors (e.g. biofilms: May disperse and seed new sites of infections) Barriers: Eyes, normal flora, mucus, stomach, urinary tract, skin 4. Invasion: - penetrate the cell (Lytic compound) - Invasiveness determine by evasion of host defences  Impact of Microbes 5. Tissue damage: Iron acquisition (Uptake) Bacteria; toxins - Iron: for bacterial growth Endotoxins: Act on specific targets, releases - express highly affinity iron uptake when bacterium lyses, or during cell growth systems 1) Siderophores: Bind iron with high affinity 2) Direct binding of Fe transport - Lipid A: endotoxin activity proteins - Activate host systems - Gram negative pathogens Exotoxin: Bound to cell (Activates host system) - Exposure: 1) Ingestion of performed exotoxin 2) Colonisation of mucosal surface/tissue 3) Colonisation of wound [All will occur toxin production] Host defences: - Eliminate non-pathogenic bacteria fast (Macrophage & other phagocytes engulf and kill) - Cytotoxic cells: kills cells infected with bacteria Host defences: Antibodies (Produced by B cells) - Prevent attachment - Clump microbes - Help phagocytosis (Opsonins) - Neutralize toxins - Attract complement system Bacterial avoidance of phagocytosis: o Resisting phagocytosis: Produce structure preventing contact o Survive inside phagocytic cells [Very pathogenic bacteria]: escape defences [Antibodies]: Antibodies avoidance Avoidance of complement - Capsules - Capsulees: prevent complement - Antigenic variation (Surface structure activation change) → Immune system x - Lipopolysaccharides (LPS) (Gram recognizes negative) hinder pore formation - Degradation of antibodies  Impact of Microbes Protists 1. Protists (Lec 4) Protists: eukaryotes [single-celled] o Have cytoskeleton for trafficking organelles Photoautotrophic (Algae): have plastids → photosynthesis Heterotrophic(Protozoa): Feed on bacteria, fungi and other protists Some mixotrophic (X cell wall) View protist cell: Microscopic count (Total cell count) [Fix motile cells] Protists occur mitosis: Genetically identical (can vary in other components) Cysts: - produced under unfavourable conditions - Highly resistance to heat, drying & radiation, antibiotics - Low water content - Dispersal mechanisms Cell wall: - Present in non- motile photosynthetic protists (Diatoms) - X in motile photosynthetic protists, hetero/mixotrophic protests [Overcome osmosis] Temperature growth: < 60oC (Membrane heat sensitive) Oxygen conc.: Obligate aerobes/anaerobes Respiration: Produce ATP (Anaerobic: hydrogenosomes)  Impact of Microbes Endosymbiont theory (Relationship): Bacteria live as endosymbiont in cells Size of bacteria: Organelle Dependency → Permanent Phylogeny relate to DNA α-proteobacterium/hydrogenosome Double membrane → Mitochondria Cyanobacterium → chloroplast Same ribosome, circular DNA Food vacuole (Phagosome) dynamics in protists Mixotrophy: Organellar mixotrophy Cellular mixotrophy Constitutive mixotrophs (Selective digestion) (X digestion) (Algae → organelle) - Eat algal cell - Eat algal cell - Evolution & complicated - Kleptoplastids (X digest - X digestion of algae genetic transfer plastids) - Algae: - Fix CO2 - Endosymbiotic alage becomes - Plastids: - Divide in cell true organelle - Fix CO2 → ‘Endosymbiosis’ - X encode polymerases (Resource in algae) (X live without them) - Plastids die and need (Live without algae) replenish (Live without plastids) Ciliate & amoebae Flagellates Movement for searching & capture prey/light  Impact of Microbes 2. Lec 5 Ciliate: - Covered in cilia - most developed protozoan - Cytostome(Mouth), cytoproct(Anus) - Nucleus: macronucleus, micronuclei Cilia: Microtubule-based hair-like organelles (Free swimming, attached) Motile cilia Non-motile cilia - 9+2, dynein motor protein - 9+0 , X dynein motor protein - ciliates - ‘Primary cilium’ on all human cells Humans [bronchial & oviduct epithelium] [Beating action] o Used for movement (Go back & forward) o Feeding: - Cytostome: Sieve (correct sized prey enter vacuoles] [‘Filter feeding’] o Suctorian ciliates: - Microtubules tentacles (End with cytostome) - Extrusomes: Secrete toxins - Dissolve prey content and suck out - Raptorial feeding (Use jaw and teeth) o Mixotrophic ciliates: - X own plastids → photoautotrophic (Organellar mixotrophy, cellular mixotrophy) Ciliate reproduction: o Asexual reproduction: - Transverse ‘binary fission’ - Involves mitosis o Sexual reproduction: - Conjugation - Micronuclei swap - Involves meiosis & mitosis - Genetic variation Cellular diversity:  Impact of Microbes Sulphur ciliates (Anaerobic ciliates) Metopus: Contain methanogenic endosymbionts (Visualized under UV light) Flagellates: - Posses flagellum/flagella (9+2) (Human: Sperm) - X backward and forward - Posses macronucleus → Longitudinal ‘binary fission’ - Aerobic - Feed by heterotrophy, photo autotrophy, mixotrophy Raptorial feeding: Naked flagellum Hispid flagellum - Create feeding current (Flagellar - Create feeding current (Flagellar movement) movement) - Less contact with base of flagellum - Prey: drawn towards base of flagellum - Less efficiency for capturing prey - Ingested via pseudopodia Increase prey capture: - Collar of tentacles (Microvilli) - Contain actin - contractile Photoautotrophic flagellates Mixotrophic flagellates (Phytoflagellates) - Own plastids (Green/golden) - Aerobic - Photosynthesis (CO2 → Glucose) - constitutive mixotrophy - Aerobic - raptorial feeding - Flagella movement towards light and - Flagella: movement & prey capture nutrients Solitary cells Colonies - Ochromonas - Dinobryon - Few plastids - plastids - feed on prey dominated cell - photosynthesize  Impact of Microbes 3. Amoebae (Lec 6) Amebae: - One macronucleus - Aerobic - heterotrophic - Asexual reproduction( X specific fission plane)\ - Move & stationery - Publicised protozoan Naked amoebae Shelled amoeba (amoeba proteus) - Move by cytoplasmic streaming - Enclosed in a shell (Test) - Produce pseudopodia on surfaces - Intrashelluar cytoplasm within test - Raptorial feeding - Extrashellular cytoplasm: move/ feed - Raptorial/diffusion feeding - produce cysts Testate amoebae Foraminiferans - Freshwater, marine& - Marine terrestrial - CaCO3 tests - Raptorial feeding - Diffusion feeding: Stationary predator captures prey with sticky extrashelluar cytoplasm (Others: radiolarians, heliozoans) Ecological impact: Good (All protists) Bad (Amoebae) - Microbes: Every food chain - Evolution of new bacterial pathogens - Keep bacterial populations healthy - ‘Reservoir’ - nutrient cycling Bacteria practice evading digestion in amoeba → pathogenic and evade our immune system  Impact of Microbes Amoebae infect human: o Entamoeba coli (In gut) (X pathogenic) → Attractive location for parasitic protists Organ/ways infected: Gut Eye Brain Sexually Blood/tissue transmitted infection diseases Reservoir Water & animas Water Warm water Humans Dogs Transport/ - Contaminated Dirty contact Flagellate Sexual Sand fly Transmission water lenses swim up nose intercourse (Vector) - Faecal-oral route Species - Entamoeba Acanthamoeba Naegleria Trichomonas Leishmania histolytica fowleri vaginalis Mexicana - Balantidium coli - Giardia lamblia Characteristics All produce cysts / ‘Brain eating - Anaerobic - Aerobic amoeba’ - X cysts - X cysts Symptoms Dysentery Keratitis Primary Trichomoniasis Leishmaniasis amoebic (Infect urethra, ‘Visceral’: vagina, prostate) Attack tissues meningoen- cephalitis (Spleen & liver) (PAM) Treatable? Treatable Treatable Fatal in two Treatable Treatable (intermittent (Lead to weeks cysts) glaucoma) Others/ / H2O2 must be / / / prevention used  Impact of Microbes Fungi Introduction to Fungi (Lec 7) Fungi: - Eukaryotes - Extremely diverse - Cell wall (Chitin & polysaccharides) - Reproduction (Both) - Heterotrophs (Absorb nutrient from environment) ▪ Saprophytes: From dead remains ▪ Necrophytes: From organism they have killed ▪ Biotrophs: From living host - Secretes enzyme & digest/absorb organic material - ‘Filamentous’ in form (Difference in cell wall composition) Growth form of fungi: Yeasts Filamentous fungi Dimorphic yeasts/fungi (Molds) - Single cell/single nucleus [Vast majority of fungi] [Transition] - Oval/Spherical - Multicellular * Medically important - Asexually reproduced - Hyphae (Bud a daughter cell) - Polarised tip growth - Aggregate → Generate light spores [Filament form: Invade → colonize/ [Dispersion] tissues] ‘pesudohyphae’ - Mycelium (Colony/ mass of hyphae) - Large complex bodies - Reproduction via spores - Saccharomyces cerevisiae - Candida albicans - Schizosaccharomyces pombe Reproduction: Asexual Sexual Yeasts Bud a daughter cell - diploid state Filamentous - light weight spores - nutrient poor supply fungi → dispersion - sexual spores: hardy structures - fast colonizing food supply - heterothallism: exchange of genetic - haploid material in different mating types - formed from specialised - homothallism: self-fertilize and produce aerial extension from mycelia sexual spores  Impact of Microbes Forms: Zygomycetes - Aseptate hyphae (Haploid) [sporangia →haploid sporangiospores] - zygospores (Diploid) - Smallest phyla -Contains Glomus spp. (Mycorrhizal fungi) Ascomycetes - Septate hyphae (Filaments) (Haploid) - Asexual: Haploid conidiospores - Sexual: Haploid ascospores - Saprophytes -Plant pathogens Basidiomycetes - Septate hyphae (Dikaryons) - Sexual: haploid basidiospores - Fruiting body - Most: saprophytes - Plant pathogens Deuteromycetes - [Asexual] spores formed in various ways - Fungi imperfecti - Ascomycetes (food spoiler, industrial workhorse)  Impact of Microbes 2. Fungi as pathogens (Lec 8) True pathogen: - Healthy host (Asymptomatic) - Adaptation: high temp, low O2 tension - Restricted to specific geographical region - Display thermal dimorphism (Yeast/hyphal form) - X obligate parasites Examples: Histoplasmosis Coccidioidomycosis (Histoplasma capsulatum) (Coccidioides immitis) 1) By inhalation 1) Digging in soil, inhalation 2) First lung , then spread to internal 2) lung infection organ 3) Arthrospores develop into spherules → endospores → Released to lung 4) meningitis & skin rashes Opportunistic pathogens: - Impaired host defences - X specific adaptation to host - World-wide distribution - prognosis: poor - species and genera increase - Superficial/benign to chronic systemic infections e.g. Candida albicans infection Aspergillosis (Candidiosis) (Aspergillus spp.) - Immunocompetent: X invasive local - Causes human diseases infection - Thermophile/ small spores - Immunocompromised: systemic causing - ‘Aspergilloma’ organ failure - Aggressive invasion → tissue necrosis - Loss of life - colonises lung/disseminates to - Invades wounds/burns brain/heart - Dimorphic yeast Dermatophytes: - superficial infectious on healthy host (X invasive) - World-wide distribution - Common form: Ringworm & athletes [Trichophyta spp. : keratin lovers (hair, skin, nails)] Control of mycoses: Azoles: ketoconazole , fluconazole (Blocks sterol demethylase → block ergosterol form) Polyenes: Nystatin, Amphotericin B (Leaky membrane form → material leak out) 5 Fluorocytosine: inhibits RNA synthesis → X fungal protein [fungistatic]  Impact of Microbes Phytopathogenic fungi (Pathogen on plants): Immature/ compromised tissue Mature and non-compromised tissue - Broad host range - High degree of host specificity - Soil-borne pathogen (Attack roots) - Aggressive invasion of root tips & [Necrotrophic pathogens] extensive destruction - Excrete toxins and cell wall digesting - Water-logged soils enzymes - Hoat cell death - Tissue invasion - Evoke host resistance mechanisms e.g. Armillaria mellea (Root rot pathogen of broad leaved trees) →Excrete ligninases, cellulose, pectinases [Biotrophic pathogens] - Maintain host viability - Limited tissue invasion - X evoke resistance mechanism - Life cycle depends on living host - Spores on leaves e.g. Puccinia graminis, Erysiphe graminis Actual problem brings: nutrient sink: reproduce photosynthesis → reduced crop yields & poor quality grain  Impact of Microbes 3. Putting fungi in good use (Lec 9) Fungi as biological control agents: 1) insect pests (glasshouses) e.g. Verticillium lecanii: - produce white spores in liquid fermenters - Fresh: sticky → attach to insects [contagious] - X ingested - Infection cycle: 1. Spore attachment 2. Germination to intersegmental region 3. Penetration of cuticle 4. Hyphal invasion beneath cuticle 5. Sporulates 6. Proliferation into blood (Yeast) 7. Death (Toxin) 8. Saprophytic stage (Spores) 2) phytopathogenic fungi (Soil) Parasitism Production of antibiotics Competition - Mycoparasites e.g. Trichoderma spp.: - Control of ‘butt rot’ in (Zygomycetes) antibiotics (trichodermin, conifers gliotoxin) - Outcompete the nutrition Method: 1) Lysis of host hyphal cell e.g. heterobasidium (Botrytis cinerea) annosum, Phlebiopsis 2) Colonisation of host gigantea (Fusarium culmorum) Fungi as tools: Yeast Soya bean products Quorn® mycoprotein - baking & brewing - Fermentation with - high protein, low fat, high - Fermentation: Aspergillus oryzae & fibre C6H12O6 → 2C2H5OH + 2CO2 Zygosaccharomyces - Grows on glucose syrup - Ammonia - Filaments: Spun, flavoured → resemble meat Saccharomyces cerevisiae Aspergillus oryzae Fusarium graminearum  Impact of Microbes Fungi as cell factories: Enzyme produced by Aspergillus niger o Glucoamylases: Liquid starch → high glucose syrup o Pectinases: Breakdown pectin in plant cell o Glucose oxidase: Food preservation , diagnostic tests (Sugar glucose) o Phytases: Improvement of animal food o Problem: High temp: high lv of acrylamide (Carcinogen) Solution: Hydrolysed Asparagine ------------------>Asparaginase Aspergillus niger o A. niger: Produce citric acid commercially (Prevent aconitase to form isocitrate) Fungi as drugs: o Penicillin (Antibiotics) o Statin: - inhibit biosynthesis of cholesterol - Reduce plasma cholesterol level  Impact of Microbes Virus 1. Viruses: general properties, structures, and hosts (Lec 10) Viruses: Simple, miniscule, infectious, obligate intracellular parasite comprising of genetic material surrounded by protein coat deprived from a host cell membrane. Genetic material of virus: DNA & RNA (Convert protein) Virus existence in 2 states: o Intracellular virus (After infecting the host cell) [Replication] o Extracellular Virion (Outside host cell) [Transmission] Shapes of capsid: 1) Helical 2) Polyhedral 3) Binal Function of capsid: 1) Protects nucleic acid being digested 2) Attach to the host cell → penetrate host cell membrane Viruses come in a variety of shapes that reflect their evolution to target specific cells in their intended hosts Hosts for viruses : 1) Bacteria (T4 bacteriophages) 2) Protozoa 3) Algae 4) Fungi (Phycodnaviridae infect algae →Infect human) 5) Plants (x to humans) 6) Animal (can transmit through human-zoonotic) 7) Virophage (Virus that infect virus)  Impact of Microbes Bacteriophages: Replication of lytic Bacteriophage T4: 1. Adsorption (To receptors) 2. Penetration (Inject nucleic acid) 3. Replication (Synthesis of material and combine) 4. Maturation (Release of new virions) 5. Release Lytic and temp. bacteriophage: Lytic phage: Bacteriophage kill host cell Lysogenic/Temperature phage: bacteriophage x kill host cell 1. Prophage: Integrate into host’s chromosome (By produce repressor protein [ blocks lytic genes]) 2. Replicates with host cell 3. Stresses →reactivate the lytic cycle Phages in biomedicine: 1) EBI (Used on unprocessed foods) 2) Bacteriophage enzyme 3) Display of immunodominant region of HBV on bacteriophage H7 Quantifying bacteriophage: Agar plate with E. coli Viruses benefits and disadvantages: Advantages Disadvantages 1) Planetary Force 1) Impact of health 2) Control the amount of bacteria  Impact of Microbes 2. Classification and replication of viruses (Lec 11) Taxonomy for viruses: 1. International Committee on Taxonomy of viruses (ICTV) Phenotypic Genotypic Molecular composition of Sequence similarity genome Gene contents Virion/Capsid structure Gene synteny Presence of an envelope Gene expression system Host range Phylogenetic relationship Pathogenicity 2. Baltimore System of virus classification [Viral genome must make mRNA which can read by ribosomes] - mRNA: +ssRNA (ribosome ready) → translated into protein - +dsDNA - complementary: - (minus) Infection pathway: - Transformation into tumour cell - Lysis - Persistent infection (Slow release of virus, X cell death) - Latent infection (→ Lytic infection)  Impact of Microbes Virus life cycle: 1. Entry: Viruses attach the receptors (Exception fungal viruses & plants) - Different viruses can bind to same receptors - Viruses (Same family) with different receptors - Multiple receptors for one virus Mechanism: - Injection of nucleic acid - Fusion of envelope with host membrane - Endocytosis 2. Replication: - Viral Protein: Synthesis of mRNA (unanimous) - Viral Genome: Generation of viral genetic material (Virus-dependent) 3. Exit: 1. Virus insert viral glycoprotein on the Surface of the membrane 2. Capsid migrate the cell membrane →Evaluate 3. Virus escape and release with host membrane (Viral adhesion)  Impact of Microbes Viruses of human/animals, prions, and viroid (Lec 12) Historical perspective of viruses: - genome of dinosaurs - oldest form of biomaterial (Billions years old) Diseases of animal/human : o Rhabdoviruses: (Rabies virus) (Gp V virus) (-ssRNA) Wide host range: mammals Infection of human via saliva Virus enters peripheral nervous system, migrates to central nervous system Swelling of the brain [Encephalitis] 1) Virus enters tissue from saliva of biting animal 2) Virus replicates and moves up to peripheral nervous system 3) Virus ascends spinal cords → reaches brain 4) Virus enters salivary glands and other organs Furious rabies Dumb rabies - Change in behaviour and voices - Predominantly paralytic - Paralytic stage - Lapse into stage of sleepiness - Death -Death (Within 3 days)  Impact of Microbes o Monkeypox (Gp I virus, dsDNA) First identified: Denmark, 1958 in monkeys First Human case: 1970 in Africa(Child) Endemic in Central & West Africa Transmission: - Animal to human: Bites and scratches - Handling of infected animal products - Human to human: Skin to skin touch - Indirect contact with contaminated fomites Skin presentation & progression of monkeypox Smallpox/Monkeypox vaccines: - ACAM2000 -live vaccina virus: (X recommend) Single dose , can replicate, can spread from vaccine to contacts (Post vaccination cardiac adverse events) - Modified vaccina Ankara(MVA): (Recommend) 2 doses subcutaneous 4 week apart, X replicate - LC 16m8 (Modified vaccina virus): Single doses , less replication ability  Impact of Microbes Viroid: Infectious agents that resemble viruses - Small known pathogen - Small circular ssRNA - Extracellular form naked= X Capsid - Resistant to proteases and nucleases - Infect plants - X Encode proteins - Mode of action: Unknown (Autonomously replicated) Prions(Spongiform Encephalopathies): Small proteinaceous infectious particles which resist inactivation & X genetic material Localise on neuron synapses between neurons/ Facilitate the uptake of copper into cell Caused by accumulation of misfold proteins scrapie prion proteins 1. Glycoprotein PrPc found healthy animal neurons 2. Interaction between PrPsc and PrPc 3. Conversion of PrPc to PrPsc (Change of folding pattern) 4.1. Accumulation of aggregated PrPsc → Abnormal function 4.2 Differently folded form exists: Generation: - Spontaneously - From mutant PrPc - Inoculation of PrPsc  Impact of Microbes Diseases: Animal Sheep (Scrapie) Cattle (BSE) - Degenerative, fatal - Mad cow disease disease of CNS - Classical BSE, H-type - X treatment available atypical BSE and L-type - Selective breeding for atypical BSE genetic resistance, - Classical BSE: Transmitted surveillance, and to human through depopulation consumption of (Control disease) contaminated meat → Creutzfeldt-Jakob disease Humans - Kuru (Trembling) - CJD : - Via ‘funerary (Creutzfeldt-Jacob Disease) cannibalism” - Lose ability to think and move properly - Suffer from memory loss