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Here's a concise overview of the requested topics: 1. Microbial World and You Naming and Classifying Microbes Binomial Nomenclature: Genus. species=E. coli; The naming system assigns each organism a two-part Latin name. For example, Escherichia coli (E. coli) refers to a ba...

Here's a concise overview of the requested topics: 1. Microbial World and You Naming and Classifying Microbes Binomial Nomenclature: Genus. species=E. coli; The naming system assigns each organism a two-part Latin name. For example, Escherichia coli (E. coli) refers to a bacterium found in the intestines of warm-blooded organisms. Hierarchy of Classification: Kingdom, Phylum, Class, Order, Family, Genus, Species. Taxonomy: Science of classifying organisms, providing universal names, and placing them into categories. Types of Microbes Bacteria: Single-celled, prokaryotic organisms with peptidoglycan cell walls. Some are motile by flagella. Archaea: Prokaryotic but distinct from bacteria. Found in extreme environments like hot springs (thermophiles) and salt flats (halophiles). Fungi: Eukaryotic organisms, including yeasts (unicellular) and molds (multicellular), that decompose organic material. Protozoa: Single-celled eukaryotes that often move by pseudopods, cilia, or flagella. Algae: Photosynthetic eukaryotes, critical to aquatic food chains and oxygen production. Viruses: Acellular, obligate intracellular parasites made of nucleic acids (DNA or RNA) surrounded by a protein coat. Multicellular Animal Parasites: Includes helminths (worms) that affect human health. Classification of Microbes Domains: ○ Bacteria: Unicellular prokaryotes with peptidoglycan walls. ○ Archaea: Prokaryotes without peptidoglycan, often extremophiles. ○ Eukarya: Includes protists, fungi, plants, and animals. Spontaneous Generation Debate Proponents: Believed life could arise from nonliving matter (e.g., John Needham boiled broth, which later became cloudy). Opponents: Advocated biogenesis—life from preexisting life (e.g., Francesco Redi demonstrated maggots arise from eggs laid by flies). Pasteur’s S-neck Flask Experiment Showed that microbes, not air, caused contamination. Sterile broth remained free of microorganisms as long as the flask's neck trapped airborne particles. Koch’s Postulates Establishes a causal link between a microbe and a disease: 1. The pathogen must be present in all cases of the disease. 2. The pathogen must be isolated and grown in pure culture. 3. The cultured pathogen must cause the disease when introduced into a healthy host.  4. The same pathogen must be re-isolated from the diseased host. Vaccination Edward Jenner used material from cowpox lesions to immunize against smallpox, laying the foundation for immunology. 3. Observing Microorganisms Through a Microscope Types of Microscopes 1. Compound Light Microscope: Uses visible light and glass lenses; magnifies up to ~1000x. 2. Phase-Contrast: Enhances contrast in transparent specimens without staining. 3. Fluorescence Microscope: Uses UV light to view fluorescently labeled structures. 4. Electron Microscope: ○ Transmission (TEM): Visualizes internal structures with high resolution. ○ Scanning (SEM): Produces 3D images of surface structures. Resolution & Magnification Resolution: Determined by the wavelength of light and numerical aperture of lenses. The shorter the wavelength, the higher the resolution. Magnification: Total magnification = Objective lens magnification × Ocular lens magnification. Preparing Smears for Staining 1. Spread the specimen thinly on a slide and air dry. 2. Heat fix to adhere the sample to the slide and kill bacteria. 3. Apply stains to visualize structures. Types of Stains Simple Stain: Uses a single dye for visualization (e.g., methylene blue). Differential Stain: Highlights differences between cell types. Examples: ○ Gram Stain: Differentiates Gram-positive (purple) and Gram-negative (pink) bacteria. ○ Acid-Fast Stain: Identifies mycobacteria (e.g., Mycobacterium tuberculosis). Special Stains: Visualize specific structures: ○ Endospore stain (spore-forming bacteria). ○ Capsule stain (polysaccharide capsules). 4. Prokaryotic and Eukaryotic Cells Functional Anatomy 1. Bacterial Cell Sizes, Morphology, and Arrangements: ○ Shapes: Cocci, bacilli, spirilla. ○ Arrangements: Chains, clusters, pairs. 2. Prokaryotic Cell Structures and Functions: ○ Cell wall, plasma membrane, ribosomes, nucleoid, pili, flagella, capsule, endospores. 3. Cell Wall: ○ G+: Thick peptidoglycan, teichoic acids. ○ G−: Thin peptidoglycan, outer membrane, lipopolysaccharides (LPS). 4. Movement Across Membranes: ○ Passive (diffusion, osmosis) and active transport. 5. Endospore Formation: ○ Protective, dormant structures formed by some bacteria under stress. 6. Eukaryotic Cell Structures: ○ Nucleus, organelles (ER, Golgi, mitochondria, chloroplasts), cytoskeleton, plasma membrane. Prokaryotic Cell Features 1. Cell Wall: ○ Gram-Positive: Thick peptidoglycan layer, teichoic acids. ○ Gram-Negative: Thin peptidoglycan, outer membrane with lipopolysaccharides (LPS). 2. Plasma Membrane: Semi-permeable barrier for nutrient and waste transport. 3. Ribosomes: Site of protein synthesis (70S ribosomes). 4. Flagella and Pili: Enable motility and attachment. 5. Capsules: Prevent phagocytosis and aid in adhesion. 6. Endospores: Resistant structures that protect DNA under extreme conditions. Eukaryotic Cell Features 1. Nucleus: Encloses DNA. 2. Organelles: ○ Mitochondria: ATP production via oxidative phosphorylation. ○ Chloroplasts: Photosynthesis in plants and algae. ○ ER and Golgi Apparatus: Protein and lipid processing and transport. 3. Cytoskeleton: Maintains shape and facilitates intracellular movement. 5. Microbial Metabolism Enzymes and Reactions 1. Structure: ○ Apoenzyme: Protein portion. ○ Cofactor/Coenzyme: Non-protein helpers (e.g., metal ions, vitamins). ○ Holoenzyme: Complete, active enzyme. 2. Mechanism: ○ Enzymes lower activation energy by stabilizing the transition state. ○ Substrate binds to the enzyme’s active site, forming an enzyme-substrate complex. 3. Factors Affecting Enzyme Activity: ○ Temperature, pH, substrate concentration, and inhibitors (competitive vs. non-competitive). ATP Generation 1. Substrate-Level Phosphorylation: Direct transfer of a phosphate group to ADP. 2. Oxidative Phosphorylation: ATP synthesis powered by electron transport and chemiosmosis. 3. Photophosphorylation: Light energy drives ATP production in photosynthetic organisms. Key Pathways 1. Glycolysis: ○ Occurs in the cytoplasm. ○ Converts glucose to 2 pyruvate, producing 2 ATP and 2 NADH. 2. Krebs Cycle (Citric Acid Cycle): ○ Produces 2 ATP, 6 NADH, and 2 FADH₂ per glucose molecule. 3. Electron Transport Chain (ETC): ○ Takes place in the inner mitochondrial membrane (eukaryotes) or plasma membrane (prokaryotes). ○ Oxygen (or other final electron acceptors) facilitates ATP production via a proton gradient. 4. Fermentation: ○ Anaerobic; regenerates NAD+ for glycolysis. Produces lactic acid or ethanol. Respiration Types 1. Aerobic: Oxygen is the final electron acceptor (e.g., humans). 2. Anaerobic: Inorganic molecules like nitrate or sulfate serve as final electron acceptors (e.g., certain bacteria). Photosynthesis 1. Light Reactions: Capture light to generate ATP and NADPH. 2. Calvin Cycle: Fixes CO₂ into glucose using ATP and NADPH. Trophic Classifications 1. Photoautotrophs: Use sunlight and CO₂ for energy and carbon. 2. Chemoautotrophs: Use inorganic compounds like hydrogen sulfide or ammonia. 3. Heterotrophs: Obtain energy and carbon from organic compounds. 6. Microbial Growth Physical and Chemical Requirements 1. Physical: ○ Temperature: Psychrophiles (cold-loving), mesophiles (moderate temperatures), thermophiles (heat-loving). ○ pH: Acidophiles, neutrophiles, alkaliphiles. ○ Osmotic Pressure: Halophiles thrive in high salt concentrations. 2. Chemical: ○ Carbon, nitrogen, sulfur, and phosphorus are essential macronutrients. ○ Trace elements (iron, magnesium, etc.) act as enzyme cofactors. Types of Media 1. Selective Media: Suppress unwanted microbes while promoting the growth of desired ones (e.g., MacConkey agar for Gram-negative bacteria). 2. Differential Media: Differentiate species based on biochemical characteristics (e.g., blood agar for hemolysis). 3. Enrichment Media: Enhance the growth of a specific microbe from a mixed population. Pure Cultures Techniques like streak plating isolate individual colonies for pure culture growth. Bacterial Division and Growth 1. Binary Fission: DNA replication followed by cell division, producing two identical daughter cells. 2. Generation Time: The time it takes for a population to double. Growth Phases 1. Lag Phase: Metabolic activity without division as cells adjust to new conditions. 2. Log Phase: Rapid exponential growth; most metabolically active phase. 3. Stationary Phase: Nutrient depletion and waste accumulation slow growth. 4. Death Phase: Cells die faster than they reproduce. Measuring Growth 1. Direct Methods: ○ Plate counts (colony-forming units, CFUs). ○ Filtration (concentrates microbes on a filter). ○ Microscopic counts using a hemocytometer. 2. Indirect Methods: ○ Turbidity (measured via spectrophotometry). ○ Metabolic activity (e.g., acid or gas production). 7. Control of Microbial Growth 1. Microbial Death Rate: ○ Microbial death refers to the permanent loss of reproductive ability in a population under a specific set of environmental conditions. ○ Death occurs logarithmically; for example, if 90% of the population dies per minute, 10% survives each successive minute. 2. Actions of Microbial Control Agents: ○ Alteration of membrane permeability: Damage to lipids or proteins in the plasma membrane causes cellular contents to leak out. ○ Denaturation of proteins: Heat or chemicals cause proteins to lose their shape, disrupting enzymatic activity. ○ Damage to DNA/RNA: Radiation or chemical agents prevent replication or transcription, halting microbial reproduction. 3. Physical Methods of Microbial Control: ○ Heat: Denatures proteins and disrupts membranes. Moist Heat: Kills by coagulating proteins. Autoclaving: 121°C at 15 psi for 15–30 minutes sterilizes tools and media. Pasteurization: Reduces spoilage microbes in food and beverages without sterilizing (e.g., 72°C for 15 seconds). Dry Heat: Oxidizes organic molecules. Methods: Direct flaming, incineration, hot air ovens (170°C for 2 hours).  ○ Filtration: Removes microbes from liquids or air by passing through filter pores (common pore size: 0.22 μm for bacteria). ○ Radiation: Ionizing radiation (e.g., X-rays, gamma rays): Causes DNA breaks. Non-ionizing radiation (e.g., UV light): Causes thymine dimers in DNA. ○ Thermal Definitions: Thermal Death Time (TDT): Time to kill all microbes at a set temperature. Thermal Death Point (TDP): Minimum temperature to kill all microbes in 10 minutes. Decimal Reduction Time (D-value): Time to reduce microbial numbers by 90% at a specific temperature. 4. Disk Diffusion Method: ○ Paper disks soaked in antimicrobial agents are placed on an agar plate inoculated with a test microbe. ○ Zones of inhibition indicate effectiveness, measured in millimeters. 5. Disinfectants: ○ Phenolics: Effective against many bacteria; disrupt membranes and denature proteins. ○ Alcohols: Effective against bacteria and enveloped viruses; dissolve lipids and denature proteins. ○ Halogens: Iodine: Inactivates proteins by iodination. Chlorine: Forms hypochlorous acid, which oxidizes molecules. ○ Quaternary Ammonium Compounds: Cationic detergents that disrupt plasma membranes and denature proteins. ○ Soaps and Detergents: Aid in mechanical removal of microbes by emulsifying fats. Sterilization and Disinfection 1. Sterilization: Complete removal or destruction of all forms of microbial life (including endospores). ○ Methods: Autoclaving, dry heat, filtration, ionizing radiation. 2. Disinfection: Reduces microbial populations to safe levels but may not eliminate all pathogens. ○ Methods: Chemical disinfectants, boiling, UV radiation. 3. Antisepsis: Application of antimicrobial agents to living tissue to prevent infection. 4. Sanitization: Reduction of microbial populations to acceptable levels (e.g., utensils in restaurants). Physical Methods 1. Heat: ○ Moist Heat: Autoclaving (121°C, 15 psi, 15 min), boiling, pasteurization. ○ Dry Heat: Incineration, hot air ovens. 2. Filtration: ○ Membrane filters for liquids and air (HEPA filters). 3. Radiation: ○ Ionizing Radiation: Gamma rays, X-rays (for deep penetration). ○ Non-Ionizing Radiation: UV light (damages DNA, limited to surface sterilization). 4. Low Temperatures: Refrigeration and freezing inhibit growth but do not kill microbes. 5. Desiccation: Removal of water to halt metabolism. 6. Osmotic Pressure: High salt or sugar concentrations cause plasmolysis. Chemical Methods 1. Disinfectants and Antiseptics: ○ Phenolics, alcohols, halogens (chlorine, iodine), heavy metals (silver, copper). 2. Sterilants: Gaseous agents (ethylene oxide). 3. Surface-Active Agents: Soaps and detergents. 4. Preservatives: Organic acids, nitrates/nitrites.  8. Microbial Genetics 1. DNA Replication: ○ Prokaryotic Process: 1. Initiation: Helicase unwinds DNA at the origin of replication. Single-strand binding proteins (SSBs) stabilize the unwound strands. Primase synthesizes RNA primers for DNA polymerase III. 2. Elongation: Leading strand synthesized continuously by DNA polymerase III. Lagging strand synthesized discontinuously as Okazaki fragments. 3. Termination: DNA polymerase I replaces RNA primers with DNA. Ligase joins Okazaki fragments. 4. Eukaryotic DNA Replication Differences: Multiple origins of replication. Telomeres protect chromosome ends. 2. Transcription: ○ DNA → mRNA using RNA polymerase. ○ Steps: 1. Initiation: RNA polymerase binds to the promoter region. 2. Elongation: RNA polymerase synthesizes RNA complementary to the DNA template strand. 3. Termination: Polymerase releases RNA transcript when it reaches the terminator sequence. 3. Translation: ○ mRNA → Polypeptides. ○ Key Players: 1. mRNA: Template with codons. 2. tRNA: Delivers amino acids; anticodon pairs with mRNA codon. 3. rRNA: Forms the ribosome. ○ Steps: 1. Initiation: Ribosome assembles at start codon (AUG). 2. Elongation: tRNA brings amino acids to the ribosome; peptide bonds form. 3. Termination: Ribosome dissociates at stop codon (UAA, UAG, UGA). 4. Mutations: ○ Point Mutation: Single base change (e.g., substitution). ○ Frameshift Mutation: Insertions or deletions shift the reading frame. 5. Gene Transfer Methods: ○ Conjugation: Plasmid transfer via pilus. ○ Transduction: Bacteriophage transfers DNA. ○ Transformation: Uptake of naked DNA from the environment. 9. Biotechnology 1. Recombinant DNA (rDNA): ○ Combining DNA from different sources to create genetic modifications. 2. Restriction Enzymes: ○ Cut DNA at specific sequences, creating sticky or blunt ends. 3. PCR: ○ Steps: Denaturation, annealing, extension. 4. Inserting DNA into Cells: ○ Methods: Transformation, electroporation, microinjection, gene guns, viral vectors. 5. Gene Libraries: ○ Collections of cloned DNA fragments representing an organism's genome. 6. Southern Blotting: ○ Identifies specific DNA sequences in a sample using labeled probes. 1. Recombinant DNA Technology: ○ Combines DNA from two sources, often using vectors (e.g., plasmids). 2. Restriction Enzymes: ○ Recognize specific palindromic DNA sequences and cut DNA. 3. PCR (Polymerase Chain Reaction): ○ Amplifies specific DNA sequences. ○ Steps: Denaturation: 94–98°C, separates DNA strands. Annealing: 50–65°C, primers bind to target sequence. Extension: 72°C, DNA polymerase synthesizes new strand. 4. Gel Electrophoresis: ○ Separates DNA fragments by size using an electric field; smaller fragments travel further. 5. Southern Blotting: ○ Transfers DNA from gel to membrane for hybridization with labeled probes. DNA Structure and Replication 1. DNA Structure: ○ Double helix, antiparallel strands, complementary base pairing (A-T, G-C). 2. Replication: ○ Semi-conservative process involving helicase, DNA polymerase, ligase. RNA and Protein Synthesis 1. Transcription: ○ DNA → RNA. ○ Key enzyme: RNA polymerase. 2. Translation: ○ RNA → Protein. ○ Occurs at ribosomes; mRNA codons dictate the amino acid sequence with tRNA. Gene Expression Regulation 1. Operons: ○ Inducible Operon: (e.g., lac operon) activated by substrate presence. ○ Repressible Operon: (e.g., trp operon) inhibited by excess product. Mutations  1. Types: ○ Point mutations (substitutions), frameshift mutations (insertions or deletions). 2. Causes: ○ Spontaneous, radiation, chemicals. Genetic Transfer 1. Transformation: Uptake of foreign DNA from the environment. 2. Conjugation: Direct DNA transfer via pilus. 3. Transduction: Bacterial DNA transfer by a virus. 10. Classification of Microorganisms 1. 3 Domains: ○ Bacteria: Prokaryotic, peptidoglycan cell walls. ○ Archaea: Prokaryotic, extreme environments, no peptidoglycan. ○ Eukarya: Eukaryotic organisms. 2. Biochemical Tests: ○ Identify metabolic characteristics. 3. Serology: ○ Detects antigens or antibodies using tests like ELISA and Western blotting. 4. DNA Fingerprinting: ○ Compares DNA patterns for identification. 5. Cladograms: ○ Visual representations of evolutionary relationships. 20. Chemotherapy 1. Spectrum of Antimicrobial Activity: ○ Broad-spectrum: Effective against many types. ○ Narrow-spectrum: Effective against specific types. 2. Modes of Action: ○ Inhibit Cell Wall Synthesis: (e.g., Penicillin). ○ Disrupt Membranes: (e.g., Polymyxins). ○ Inhibit Protein Synthesis: (e.g., Tetracyclines). ○ Inhibit Nucleic Acid Synthesis: (e.g., Rifampin). ○ Antimetabolites: Disrupt metabolic pathways (e.g., Sulfa drugs). 3. Antifungal Drugs: ○ Target ergosterol in fungal membranes. 4. Antiviral Drugs:  ○ Block viral entry, replication, or release. 5. Disk Diffusion, MIC, MBC: ○ MIC: Minimum inhibitory concentration. ○ MBC: Minimum bactericidal concentration. 6. Drug Resistance: ○ Caused by mutations or acquisition of resistance genes. ○ Strategies include efflux pumps, target modification, and enzymatic drug destruction. 11. Prokaryotes Proteobacteria General Characteristics: Largest phylum of bacteria, Gram-negative, diverse metabolic and ecological Classes of Proteobacteria: Alpha-proteobacteria: Key features: Often oligotrophic (adapted to low-nutrient environments). Examples: Rhizobium: Forms nitrogen-fixing nodules on legumes. Rickettsia: Obligate intracellular parasites, cause diseases like typhus and Rocky Mountain spotted fever. Beta-proteobacteria: Metabolize organic substances from decomposing matter. Examples: Burkholderia cepacia: Opportunistic pathogen in cystic fibrosis patients. Neisseria gonorrhoeae: Causes gonorrhea. Gamma-proteobacteria: Largest and most diverse class. Examples: ○ Escherichia coli: Normal gut microbiota, but some strains are pathogenic. ○ Pseudomonas aeruginosa: Opportunistic pathogen in immunocompromised individuals. ○ Vibrio cholerae: Causes cholera. Delta-proteobacteria: Include bacterial predators and sulfate reducers. Examples: ○ Bdellovibrio: Preys on other bacteria. ○ Desulfovibrio: Involved in the sulfur cycle, reduces sulfate to hydrogen sulfide. Epsilon-proteobacteria: Helical or curved bacteria, often microaerophilic. Examples: ○ Helicobacter pylori: Causes peptic ulcers and has been linked to gastric cancer. Spirochetes Structure: Thin, flexible, helical bacteria. Motility: Axial filaments (endoflagella) allow a corkscrew-like movement. Pathogenic Species: ○ Treponema pallidum: Causes syphilis. ○ Borrelia burgdorferi: Causes Lyme disease. Habitat: Many are free-living in aquatic or soil environments, while others are pathogens or commensals. Bacteroidetes Key Features: ○ Gram-negative, obligate anaerobes. ○ Dominant in the human gut microbiome, essential for digesting complex carbohydrates. ○ Examples: ○ Bacteroides fragilis: Important in gut homeostasis but can cause infections if introduced to sterile areas. Archaea Distinctive Traits: ○ Lack peptidoglycan in cell walls; instead, they have pseudopeptidoglycan or S-layer proteins. ○ Membranes composed of ether-linked lipids, which provide stability in extreme conditions. Types of Extremophiles: ○ Thermophiles: Thrive at high temperatures (e.g., Thermococcus). ○ Halophiles: Require high salt concentrations (e.g., Halobacterium). ○ Methanogens: Produce methane as a metabolic byproduct (e.g., Methanobrevibacter). 12. Fungi & Protozoa Fungi Characteristics: Eukaryotic, chitin cell walls, heterotrophic (saprophytic or parasitic). Hyphae Types: ○ Septate hyphae: Divided by cross-walls. ○ Aerial hyphae: Produce spores. ○ Vegetative hyphae: Absorb nutrients. Life Cycle: ○ Asexual: Spore formation (e.g., conidia, sporangia). ○ Sexual: Plasmogamy → karyogamy → meiosis. Diseases: Mycoses (e.g., athlete’s foot, candidiasis, aspergillosis). Protozoa Eukaryotic, unicellular, diverse in form and metabolism. Malaria: Plasmodium species infect human liver cells and erythrocytes, transmitted by Anopheles mosquitoes. Euglena: Flagellated protozoan, photosynthetic and heterotrophic. Sexual Reproduction: Includes conjugation or gamete fusion in some species. Fungi Cellular Structure: ○ Chitin-based cell walls provide rigidity.  Cytoplasmic components include nuclei, mitochondria, and vacuoles. Nutrition: ○ Absorptive heterotrophs; secrete enzymes to break down complex organic materials. Reproduction: ○ Asexual: Fragmentation, budding, or spore production (e.g., conidiospores, sporangiospores). ○ Sexual: Plasmogamy: Cytoplasmic fusion of two mating types. Karyogamy: Fusion of nuclei. Meiosis: Produces genetically diverse spores. Clinical Significance: ○ Fungal infections (mycoses) range from superficial (e.g., ringworm) to systemic (e.g., histoplasmosis). Protozoa Modes of Locomotion: ○ Flagella (e.g., Trypanosoma), cilia (e.g., Paramecium), pseudopodia (e.g., Amoeba). Reproduction: ○ Asexual: Binary fission, schizogony (multiple fissions). ○ Sexual: Conjugation (exchange of micronuclei in ciliates) or gamete fusion. Pathogenic Protozoa: ○ Plasmodium: Causes malaria; infects red blood cells and liver cells. ○ Giardia lamblia: Causes giardiasis, a diarrheal disease. 13. Viruses Structure and Function Acellular, consist of nucleic acid (DNA or RNA), capsid (protein coat), sometimes an envelope with glycoproteins. Growing Viruses Require living cells (cell cultures, embryonated eggs, live animals). Viral Multiplication 1. Attachment: Virus binds to host cell. 2. Penetration: Entry via endocytosis or fusion. 3. Uncoating: Nucleic acid released. 4. Replication: Viral genome is copied. 5. Assembly: Virions are constructed. 6. Release: Budding (enveloped viruses) or lysis. Lysogenic Cycle Virus integrates into the host genome as a prophage, remaining dormant until triggered. SARS-CoV-2 Etiology: Causes COVID-19. Epidemiology: Pandemic; spread globally with high mortality in vulnerable populations.  Structure: RNA virus, enveloped with spike proteins. Portals of Entry: Respiratory tract; spread via droplets and aerosols. Pathogenesis: Binds ACE2 receptor, damages lungs and other tissues. Progression: Incubation → mild/moderate → severe (ARDS, organ failure). Diagnosis: PCR, antigen tests. Treatment: Antivirals, supportive care. Vaccination: mRNA (Pfizer, Moderna), vector-based (J&J). Structure and Function Capsid Types: ○ Helical, icosahedral, or complex (e.g., bacteriophages). Genome Types: ○ DNA or RNA, single-stranded or double-stranded, segmented or non-segmented. Envelopes: Lipid-based, derived from the host cell membrane, often with viral glycoproteins for attachment. Life Cycles: Lytic Cycle: Host cell is lysed, releasing virions. Lysogenic Cycle: Viral genome integrates into the host genome as a prophage. SARS-CoV-2 (COVID-19): Genome: Single-stranded positive-sense RNA. Pathogenesis: ○ Spike protein binds ACE2 receptors in human cells. ○ Infection leads to inflammation, ARDS (acute respiratory distress syndrome), and multiorgan involvement in severe cases. Public Health Impact: ○ Global pandemic with significant morbidity and mortality. ○ Vaccination campaigns (e.g., mRNA vaccines) have been pivotal in controlling spread. 14. Epidemiology Classifying Infectious Diseases Acute, chronic, latent, communicable, noncommunicable. Development of Disease Incubation → prodromal → illness → decline → convalescence. Transmission Direct (contact), indirect (fomites), vector-borne. Vectors Biological (mosquitoes) or mechanical (flies). Nosocomial Infections Hospital-acquired infections (HAIs), often due to resistant microbes.  Basic Reproductive Number (R₀): Average number of secondary infections caused by a single infected individual. Mortality Rate: Deaths from a disease per total population. Morbidity Rate: Number of individuals affected by a disease per total population. 15. Pathogenicity 1. Adherence: Microbes attach via adhesins (e.g., fimbriae). 2. ID50: Infectious dose for 50% of the population. 3. Endotoxins: Lipid A of LPS in Gram-negative bacteria; trigger inflammation. 4. Exotoxins: Secreted proteins with specific targets (e.g., neurotoxins, enterotoxins). 5. Parenteral Route: Pathogen bypasses barriers (injections, wounds). 6. M Protein: Virulence factor in Streptococcus aiding immune evasion. 7. Cytopathic Effects: Virus-induced damage, e.g., syncytia, inclusion bodies.