Comprehensive Study Guide for General Microbiology (BIO 240)

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Introduction to Microbiology

Living and Non-Living Microbial Forms

Microbiology studies both living and non-living entities, including bacteria, viruses, protozoa, and others. Each group has unique characteristics and sizes, distinguishing them from one another.

Bacteria: Unicellular, prokaryotic, typically 0.5–5 μm in size.
Viruses: Non-living, acellular, much smaller (20–300 nm), require host cells for replication.
Protozoa: Unicellular, eukaryotic, larger than bacteria (10–50 μm).
Fungi: Eukaryotic, can be unicellular (yeasts) or multicellular (molds).
Helminths: Multicellular parasitic worms.

Distinguishing Features: Cell structure, replication method, metabolism, and pathogenicity.

Example: Escherichia coli (bacterium) vs. Influenza virus.

Binomial Nomenclature

Binomial nomenclature is the formal system for naming organisms using two names: genus and species.

Genus: Capitalized, italicized (e.g., Staphylococcus).
Species: Lowercase, italicized (e.g., Staphylococcus aureus).

Example: Streptococcus pyogenes

History of Microbiology

Key figures contributed to the development of microbiology:

Antonie van Leeuwenhoek: First to observe microbes using a microscope.
Louis Pasteur: Disproved spontaneous generation, developed pasteurization.
Robert Koch: Established Koch's postulates for linking microbes to disease. MAGIC BULLET
Joseph Lister: Introduced antiseptic techniques in surgery.
Florence Nightingale: Pioneered infection control in hospitals.

Cell Structure and Function

Universal Characteristics of Cells

All cells share four universal characteristics:

Cell membrane
Cytoplasm
Genetic material (DNA or RNA)
Ribosomes

Gram-Positive vs. Gram-Negative Bacteria

Bacteria are classified based on their cell wall structure:

Gram-Positive: Thick peptidoglycan layer, teichoic acids, stains purple.
Gram-Negative: Thin peptidoglycan, outer membrane with lipopolysaccharide, stains pink.

Peptidoglycan: Composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) with peptide cross-links.

Significance: Side chains and cross-links provide structural integrity.

Cellular Structures and Their Functions

Endospores: Allow survival in harsh conditions (e.g., heat, desiccation).
Capsules, Glycocalyx, Slime Layers: Protect against phagocytosis, aid in adhesion.
Flagella: Motility.
Fimbriae: Attachment.
Pili: Conjugation and attachment.

Acid-Fast Staining: Used for Mycobacterium tuberculosis due to waxy cell wall (mycolic acids).

Bacterial vs. Eukaryotic Cells: Bacteria lack membrane-bound organelles; eukaryotes have nucleus, mitochondria, etc.

Microscopy, Staining, and Classification

Microscope Properties

Objective Lens: Magnifies specimen.
Ocular Lens: Further magnifies image.
Condenser: Focuses light on specimen.
Parfocal: Image remains in focus when switching objectives.

Total Magnification:

Immersion Oil: Reduces light refraction, increases resolution.

Heat-Fixing: Adheres cells to slide, kills cells, preserves morphology.

Staining Techniques

Simple Stain: Uses one dye; highlights cell shape.
Differential Stain: Uses multiple dyes; distinguishes cell types (e.g., Gram, acid-fast).
Gram Stain: Crystal violet, iodine, alcohol, safranin.
Acid-Fast Stain: Carbol fuchsin, acid alcohol, methylene blue.
Spore/Flagella Stains: Special stains for specific structures.

Cell Shapes: Cocci (spherical), bacilli (rod-shaped), spirilla (spiral).

Arrangements: Chains, clusters, pairs.

Infection, Infectious Disease, and Epidemiology

Definitions

Acute: Rapid onset, short duration.
Chronic: Slow onset, long duration.
Host: Organism harboring pathogen.
Iatrogenic: Disease caused by medical intervention.
Idiopathic: Unknown cause.
Mutualism: Both organisms benefit.
Parasitism: One benefits, one harmed.
Pathogenicity: Ability to cause disease.
Sequelae: Long-term consequences.
Sign: Objective evidence of disease.
Symptom: Subjective experience.
Syndrome: Group of signs/symptoms.
Virulence: Degree of pathogenicity.
Virulence Factor: Molecule aiding pathogenicity.

Virulence Factors and Enzymes

Hyaluronidase: Breaks down connective tissue.
Collagenase: Breaks down collagen.
Coagulase: Clots blood.
Streptokinase: Dissolves clots.

Endotoxin vs. Exotoxin: Endotoxins are lipopolysaccharides from Gram-negative bacteria; exotoxins are proteins secreted by bacteria.

Antiphagocytic Factors: Capsules, M protein, leukocidins.

Stages of Infectious Disease

Incubation
Prodromal
Illness
Decline
Convalescence

Each stage has distinct clinical features.

Transmission Modes

Contact: Direct, indirect, droplet.
Vehicle: Airborne, waterborne, foodborne, bodily fluids.
Vector: Biological, mechanical.

Incidence vs. Prevalence

Incidence: New cases in a time period.
Prevalence: Total cases at a given time.

Types of Disease Occurrence

Endemic: Constantly present.
Epidemic: Sudden increase.
Pandemic: Worldwide epidemic.
Sporadic: Occasional cases.

Innate Immunity

Immune Cells and Their Functions

Cell Type	Main Function	Granulocyte/Agranulocyte
Basophil	Release histamine	Granulocyte
Mast cell	Allergic response, histamine release	Granulocyte
Eosinophil	Combat parasites, allergies	Granulocyte
Lymphocyte	Adaptive immunity	Agranulocyte
Monocyte	Differentiate into macrophages	Agranulocyte
Macrophage	Phagocytosis	Agranulocyte
Neutrophil	Phagocytosis, first responders	Granulocyte

Central vs. Peripheral Lymphoid Tissue: Central (bone marrow, thymus); peripheral (lymph nodes, spleen).

Thymus: Maturation site for T lymphocytes.

Physical Barriers to Infection

Skin
Muco-ciliary escalator
Lacrimal apparatus

Phagocytosis

Chemotaxis
Adherence
Ingestion
Digestion
Exocytosis

Carried out by neutrophils, macrophages, dendritic cells.

Eosinophils: Combat parasites.

Natural Killer Cells: Destroy infected or abnormal cells.

Inflammation

Redness
Heat
Swelling
Pain

Major steps: Vasodilation, increased permeability, migration of phagocytes.

Lysozyme and Interferons

Lysozyme: Breaks down bacterial cell walls; found in tears, saliva.
Interferons: Antiviral proteins; alpha and beta (produced by infected cells), gamma (produced by T cells).

Complement System

Three activation pathways:

Classical
Alternative
Lectin

Leads to:

Opsonization
Inflammation
Membrane attack complex (MAC)

Adaptive Immunity

B vs. T Lymphocytes

B Lymphocytes: Mediate humoral immunity; produce antibodies.
T Lymphocytes: Mediate cell-mediated immunity; cytotoxic T cells and cytokines.

Key Terms

Antigen: Substance recognized by immune system.
Epitope: Specific region of antigen.
Antigen Receptor: B cell (antibody), T cell (TCR).

Properties of Adaptive Immunity

Specificity
Diversity (achieved by gene recombination)
Memory
Self-tolerance

Effector vs. Memory Cells: Effector cells act immediately; memory cells persist for future responses.

Primary vs. Secondary Response: Primary is first exposure; secondary is faster, stronger.

Plasma Cell: Effector B cell producing antibodies.

Types of T Lymphocytes

Type	Main Function	CD Marker	MHC Binding
Helper T (Th)	Activate other cells	CD4	MHC II
Cytotoxic T (Tc)	Kill infected/tumor cells	CD8	MHC I
Regulatory T (Treg)	Suppress immune response	CD4	MHC II

Cytokines: Signaling proteins, associated with helper T cells.

Perforins: Proteins used by cytotoxic T cells to lyse target cells.

Bacterial Diseases

Exotoxins and Endotoxins

Endotoxin: Lipid A of Gram-negative bacteria.
Exotoxin: Secreted proteins; classified as Type I, II, III.

Type I: Superantigens (e.g., TSST-1).

Type II: Membrane-disrupting (e.g., hemolysins).

Type III: A-B toxins (e.g., diphtheria toxin).

Bacterial Skin Infections

Necrotizing Fasciitis: Caused by Streptococcus pyogenes; enzymes include hyaluronidase, streptokinase.
Clostridium tetani and Clostridium botulinum: Form endospores; toxins cause tetanus and botulism.
Botulinum Toxin: Used for disease treatment (e.g., dystonia) and cosmetics (Botox).
Trismus: Lockjaw; Opisthotonos: Back arching.
Vaccines: Available for tetanus, not botulism.

Bacterial Respiratory Infections

Pharyngitis: Sore throat.
Erythema: Redness.
Exudate: Pus.
Lymphadenopathy: Swollen lymph nodes.
Streptococcus pyogenes: Causes strep throat; virulence factors include M protein, streptolysin.
Hemolysis: S. pyogenes causes beta-hemolysis on sheep blood agar.
Complications: Rheumatic fever, glomerulonephritis.

Bacterial Gastrointestinal Infections

Helicobacter pylori: Causes ulcers; virulence factors include urease, flagella; associated with gastric cancer.
Gastroenteritis: Inflammation of stomach/intestines.
Intoxication: Disease caused by preformed toxins (e.g., S. aureus).
Staphylococcus aureus: Exotoxin causes vomiting; transmitted via contaminated food.
E. coli O157:H7: Causes hemorrhagic colitis; AE lesions, intimin, shiga toxin; can cause hemolytic uremic syndrome.
Clostridium difficile: Causes antibiotic-associated diarrhea; toxins A and B damage intestine; endospores aid spread; fecal transplant restores microbiome.

Bacterial Urinary and Reproductive Infections

UTIs: Pyelonephritis (kidney), cystitis (bladder), urethritis (urethra), bacteriuria (bacteria in urine), pyuria (pus in urine), dysuria (painful urination).
E. coli: Most common cause; virulence factors include fimbriae.
Cranberry Juice: May prevent adherence of bacteria.
Syphilis: Caused by Treponema pallidum; four stages.
Chlamydia trachomatis: Atypical, obligate intracellular; elementary and reticulate bodies; silent disease; causes PID, trachoma.

Eukaryotic Pathogens

Protozoa

Mastigophorans: Flagella for movement.
Amebozoa: Pseudopodia.
Ciliates: Cilia.
Amebo-flagellates: Both pseudopodia and flagella.
Apicomplexans: Non-motile; Plasmodium causes malaria.

Trophozoite: Active form; Cyst: Dormant form.

Fungi

Cell Wall: Chitin.
Body Structure: Thallus, hyphae, mycelium.
Reproduction: Budding, asexual/sexual spores.
Nutrition: Heterotrophs.
Significance: Lichens, mycorrhizae, antibiotics, food, mycoses.

Algae

Mostly autotrophs.
Habitat: Water, some land.

Helminths

Tapeworms: Scolex (suckers/hooks), proglottids.
Roundworms: Cylindrical body.
Transmission: Ingestion, skin penetration.

Viruses and Viral Diseases

Virus Structure and Infection

Capsid: Protein shell.
Capsomere: Subunit of capsid.
Envelope: Lipid membrane from host.
Glycoprotein (spike): Attachment.
Naked Virus: Lacks envelope.

Infection Steps: Attachment, entry, replication, assembly, release.

Release: Naked viruses lyse cells; enveloped viruses bud from membrane.

Latency: Dormant state; seen in herpesviruses.

Specific Viral Diseases

Measles: Koplik's spots, maculopapular rash, airborne transmission.
Herpesvirus 1: Cold sores; Herpesvirus 2: Genital herpes; latency in nerves; acyclovir inhibits viral DNA polymerase.
Influenza: H (hemagglutinin), N (neuraminidase); antigenic shift/drift; new vaccine yearly; influenza A causes pandemics.
Monkeypox: Related to smallpox; spreads via contact; prodromal symptoms, rash progression; vaccines developed for smallpox; prevention includes hygiene.
Coronavirus: Originated from zoonotic sources; enters via ACE2 receptor; causes respiratory disease; prevention includes vaccination, masks.
West Nile Virus: Flavivirus; transmitted by Culex mosquitoes; birds are reservoir; humans are dead-end hosts; febrile vs. neuroinvasive forms; avoid blood donation post-infection.
Dengue Virus: Flavivirus; transmitted by Aedes mosquitoes; typical vs. hemorrhagic fever; pathogenesis involves immune enhancement; prevention includes mosquito control.

Controlling Microbial Growth in the Environment

Effectiveness of Antiseptics/Disinfectants

Effectiveness determined by microbial death rate, zone of inhibition, and susceptibility tests.

Moist Heat Methods: Boiling, autoclaving, pasteurization.

Terminology

Aseptic: Free from contamination.
Decontamination: Removal of microbes.
Disinfection: Destruction of pathogens.
Sterilization: Complete destruction of all microbes.

Mechanisms of Control

Alcohols: Denature proteins, disrupt membranes.
Ionizing Radiation: Damages DNA.
Non-Ionizing Radiation: UV light causes thymine dimers.

Boiling: Some spores and viruses resist boiling.

Membrane Filtration: Sterilizes heat-sensitive liquids.

Pasteurization vs. UHT Sterilization: Pasteurization reduces microbes; UHT sterilizes.

Controlling Microbial Growth in the Body: Antimicrobial Drugs

Antimicrobial Spectrum and Mechanisms

Broad Spectrum: Effective against many microbes.
Narrow Spectrum: Effective against few.
Penicillin: Inhibits cell wall synthesis.
Tetracycline: Inhibits protein synthesis.
Cephalosporin: Inhibits cell wall synthesis.
Amphotericin B: Disrupts fungal membranes.
Erythromycin: Inhibits protein synthesis.

Testing Effectiveness: Disk diffusion, MIC, MBC.

Antibiotic Resistance: Arises via mutation, transduction, conjugation, transformation.

Penicillin Resistance: Beta-lactamase production, altered targets.

Zone of Inhibition: Large zone = sensitive; regrowth (satellite colonies) = resistance.

Immunization and Immune Testing

Vaccines and Their Types

Attenuated Vaccine: Live, weakened; replicates in body (e.g., MMR).
Inactivated Vaccine: Killed; does not replicate; whole or subunit (e.g., polio).
Toxoid: Inactivated toxin (e.g., tetanus).
Adjuvant: Enhances immune response (e.g., aluminum salts).
mRNA Vaccine: Delivers mRNA encoding antigen (e.g., COVID-19 vaccines).
Viral Vector Vaccine: Uses virus to deliver antigen gene (e.g., Johnson & Johnson COVID-19 vaccine).

Contraindications: Live vaccines not for immunocompromised or pregnant.

Herd Immunity: Protection of population when enough are immune.

Resurgence: Due to reduced vaccination rates; examples include measles outbreaks.

Additional info: Academic context and definitions were expanded for clarity and completeness. Tables were recreated for cell types and T lymphocyte classification. Equations were provided in LaTeX format as required.