Comprehensive Microbiology Exam 1 Study Guide

Chapter 1: Introduction to Microbiology

Prokaryote vs Eukaryote

Understanding the differences between prokaryotic and eukaryotic cells is fundamental in microbiology.

• Prokaryotes: Unicellular organisms lacking a nucleus and membrane-bound organelles. Includes Bacteria and Archaea.

• Eukaryotes: Organisms with a true nucleus and membrane-bound organelles. Includes Animals, Plants, Fungi, and Protists.

• Key Differences: Size, complexity, presence of organelles, and methods of reproduction.

Pathogens and Opportunistic Pathogens

• Pathogen: A microorganism that causes disease.

• Opportunistic Pathogen: Normally harmless but can cause disease in immunocompromised hosts or when introduced to unusual sites.

Spontaneous Generation vs Biogenesis

• Spontaneous Generation: The disproven idea that life arises from non-living matter.

• Biogenesis: The principle that life arises only from pre-existing life. Supported by Pasteur's experiments.

Koch’s Postulates

• Set of criteria to establish a causative relationship between a microbe and a disease.

• Four postulates include: association, isolation, causation, and re-isolation.

Florence Nightingale

• Pioneer in medical hygiene and infection control.

• Demonstrated the importance of sanitation in reducing disease transmission.

Healthcare-Associated Infections (HAI)

• Infections acquired in healthcare settings.

• Prevention includes hand hygiene, sterilization, and surveillance.

Taxonomic Hierarchy and Binomial Nomenclature

• Taxonomic Hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Binomial Nomenclature: Two-part scientific naming system (Genus species), e.g., Escherichia coli.

Host-Microbe Interactions

• Parasitism: One benefits, the other is harmed.

• Mutualism: Both benefit.

• Commensalism: One benefits, the other is unaffected.

Chapter 2: Biochemistry Basics

Acids, Bases, and pH Scale

• Acid: Substance that donates protons (H+).

• Base: Substance that accepts protons.

• pH Scale: Measures hydrogen ion concentration; ranges from 0 (acidic) to 14 (basic).

• Formula: $\mathrm{pH} = -\log_{10}[\mathrm{H}^+]$

Biomolecule Classes

• Carbohydrates: Energy source and structural components.

• Lipids: Membrane structure and energy storage.

• Proteins: Enzymes, structural, transport, and regulatory roles.

• Nucleic Acids: Genetic information storage and transfer.

Protein Folding and Structure

• Primary Structure: Amino acid sequence.

• Secondary Structure: Alpha helices and beta sheets.

• Tertiary Structure: 3D folding of a single polypeptide.

• Quaternary Structure: Association of multiple polypeptides.

Chapter 3: Introduction to Prokaryotic Cells

Microbial Shapes and Arrangements

• Coccus: Spherical

• Bacillus: Rod-shaped

• Spirillum: Spiral-shaped

• Arrangements: Chains (strepto-), clusters (staphylo-), pairs (diplo-)

Plasma Membrane Structure and Function

• Phospholipid Bilayer: Selectively permeable barrier.

• Fluidity: Maintained by fatty acid composition and temperature.

Gram Positive vs Gram Negative Bacteria

• Gram Positive: Thick peptidoglycan, teichoic acids, stains purple.

• Gram Negative: Thin peptidoglycan, outer membrane with LPS, stains pink.

Diffusion and Osmosis

• Diffusion: Movement of molecules from high to low concentration.

• Osmosis: Diffusion of water across a semipermeable membrane.

Active vs Passive Transport

• Passive Transport: No energy required (diffusion, facilitated diffusion, osmosis).

• Active Transport: Requires energy (ATP) to move substances against gradient.

Flagellar Arrangements and Response

• Monotrichous: Single flagellum.

• Lophotrichous: Cluster at one end.

• Amphitrichous: One at each end.

• Peritrichous: Distributed over entire cell.

• Chemotaxis: Movement in response to chemical stimuli.

Prokaryotic Organelles and Ribosomal Size

• Ribosomes: 70S in prokaryotes (50S + 30S subunits).

• Other Structures: Nucleoid, plasmids, inclusion bodies.

Chapter 4: Introduction to Eukaryotic Cells

Endosymbiotic Theory and Eukaryotic Evolution

• Proposes that mitochondria and chloroplasts originated from engulfed prokaryotes.

• Supported by similarities in DNA, ribosomes, and reproduction.

Eukaryotic Diversity and Taxonomy

• Includes Animals, Plants, Fungi, and Protists.

• Each group has unique cellular structures and life cycles.

Eukaryotic Organelles and Functions

• Nucleus: Contains genetic material.

• Mitochondria: ATP production.

• Endoplasmic Reticulum: Protein and lipid synthesis.

• Golgi Apparatus: Protein modification and sorting.

• Lysosomes: Digestion of macromolecules.

Pathogens and Diseases Associated with Eukaryotes

• Examples: Plasmodium (malaria), Trypanosoma (sleeping sickness), Candida (yeast infections).

Ribosomal Structure

• Eukaryotic ribosomes: 80S (60S + 40S subunits).

Chapter 5: Genetics

Genomes of Prokaryotes and Eukaryotes

• Prokaryotes: Single, circular chromosome; may have plasmids.

• Eukaryotes: Multiple, linear chromosomes; organellar DNA.

Nucleotides, RNA, and Plasmids

• Nucleotides: Building blocks of DNA and RNA.

• RNA: Messenger (mRNA), transfer (tRNA), ribosomal (rRNA).

• Plasmids: Small, circular DNA molecules in prokaryotes.

Central Dogma

• Describes flow of genetic information: DNA → RNA → Protein.

DNA Replication

• Occurs in 5' to 3' direction.

• Key Enzymes: Helicase, primase, DNA polymerase, ligase, topoisomerase.

• Formula: $\text{DNA}_{\text{parent}} \xrightarrow{\text{replication}} \text{DNA}_{\text{daughter}}$

Transcription and Translation

• Transcription: DNA to RNA.

• Translation: RNA to protein.

• Start Codon: AUG (methionine).

• Stop Codons: UAA, UAG, UGA.

• Amino Acids: 20 standard types.

Operons

• Clusters of genes under control of a single promoter.

• Can be activated or deactivated by regulatory proteins.

Mutations and Mutagen Types

• Point Mutation: Single nucleotide change.

• Frameshift Mutation: Insertion or deletion shifts reading frame.

• Silent, Missense, Nonsense Mutations: Varying effects on protein.

• Mutagens: Physical (radiation), chemical, biological agents causing mutations.

Gene Transfer

• Vertical Transfer: Parent to offspring.

• Horizontal Transfer: Between organisms (transformation, transduction, conjugation).

Chapter 6: Viruses and Prions

Virus and Phage Types

• Viruses: DNA or RNA genome, protein capsid, sometimes envelope.

• Bacteriophages: Viruses that infect bacteria.

Phage Structure

• Capsid: Protein shell.

• Tail fibers: Attachment to host.

• Genome: DNA or RNA.

Antigens and Antibodies

• Antigen: Substance that elicits immune response.

• Antibody: Protein that binds specific antigens.

Antigenic Drift and Shift

• Drift: Minor genetic changes (mutations).

• Shift: Major genetic reassortment, often in influenza viruses.

Virus Taxonomy

• Classified by genome type, structure, host range.

Lytic vs Lysogenic Pathways

• Lytic: Virus replicates and lyses host cell.

• Lysogenic: Viral genome integrates into host DNA, replicates with host.

Animal Virus Replication

• Attachment, penetration, uncoating, replication, assembly, release.

Types of Infections

• Acute: Rapid onset, short duration.

• Chronic: Persistent, long-term.

• Persistent: Virus remains in host for extended periods.

Prions and Neurodegenerative Diseases

• Prions: Infectious proteins causing diseases like Creutzfeldt-Jakob and mad cow disease.

Chapter 7: Fundamentals of Microbial Growth

Bacterial Division and Growth Phases

• Binary Fission: Main method of bacterial reproduction.

• Growth Phases: Lag, log (exponential), stationary, death.

Environmental Classifications

• Temperature: Psychrophiles, mesophiles, thermophiles.

• pH: Acidophiles, neutrophiles, alkaliphiles.

• Salt: Halophiles.

• Oxygen: Obligate aerobes, obligate anaerobes, facultative anaerobes, microaerophiles, aerotolerant anaerobes.

Microbial Control Methods

• Physical: Heat, radiation, filtration.

• Chemical: Disinfectants, antiseptics.

Chapter 8: Microbial Metabolism

Carbohydrate Fermentation

• Common pathways: lactic acid fermentation, alcoholic fermentation.

• Used in food production (e.g., yogurt, bread, beer).

Chapter 9: Principles of Infectious Disease and Epidemiology

Disease Terminology and Transmission

• Infection: Invasion by pathogens.

• Transmission Modes: Direct, indirect, droplet, vector-borne, vehicle-borne.

Stages of Disease

• Incubation, prodromal, illness, decline, convalescence.

Epidemiology and Public Health

• Epidemiological Triangle: Host, agent, environment.

• Measures of Frequency: Incidence, prevalence.

• Measures of Association: Risk ratio, odds ratio.

• Analytical Epidemiology: Studies to determine cause, risk factors, and control measures.

• Emerging/Reemerging Diseases: New or increasing in incidence.

Table: Measures of Frequency and Association

Measure	Definition
Incidence	Number of new cases in a population over a period
Prevalence	Total number of cases at a given time
Risk Ratio	Risk in exposed group / risk in unexposed group
Odds Ratio	Odds of exposure in cases / odds in controls

Chapter 10: Host-Microbe Interactions and Pathogenesis

Pathogenicity and Virulence

• Pathogenicity: Ability to cause disease.

• Virulence: Degree of pathogenicity.

Infectious Dose 50 (ID50) and Lethal Dose 50 (LD50)

• ID50: Dose required to infect 50% of a population.

• LD50: Dose required to kill 50% of a population.

Toxins and Virulence Factors

• Exotoxins: Secreted proteins causing damage.

• Endotoxins: Lipid A component of LPS in Gram-negative bacteria.

• LPS/Lipid A: Triggers strong immune response.

Steps to Infection

• Entry, adherence, invasion, evasion, damage to host.

Immune Evasion Mechanisms

• Antigenic variation, capsule formation, inhibition of phagocytosis, intracellular survival.