Microbiology Final Exam Comprehensive Study Guide

Classification and Domains of Life

Three Domains of Life

The three domains of life represent the highest level of biological classification, each with unique characteristics:

• Bacteria: Prokaryotic, cell walls contain peptidoglycan, diverse metabolic pathways.

• Archaea: Prokaryotic, cell walls lack peptidoglycan, often found in extreme environments, unique membrane lipids.

• Eukarya: Eukaryotic, includes protists, fungi, plants, and animals; cells have membrane-bound organelles.

Levels of Biological Classification: Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species.

Unique Features of Microbial Groups

• Algae: Photosynthetic eukaryotes, found in aquatic environments.

• Viruses: Acellular, require host cells for replication, contain DNA or RNA.

• Protozoa: Unicellular eukaryotes, often motile, diverse life cycles.

• Fungi: Eukaryotic, cell walls contain chitin, includes yeasts and molds.

• Bacteria: Prokaryotic, diverse shapes and metabolic capabilities.

• Archaea: Prokaryotic, unique biochemistry, often extremophiles.

Cell Structure and Morphology

Bacterial Morphology

Bacteria exhibit various shapes and arrangements:

• Coccus: Spherical

• Bacillus: Rod-shaped

• Spirillum: Spiral-shaped

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

Prokaryotic vs Eukaryotic Cells

• Prokaryotes: No nucleus, no membrane-bound organelles, smaller size.

• Eukaryotes: Nucleus present, membrane-bound organelles, larger size.

Gram-Positive vs Gram-Negative Bacteria

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

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

Function: Gram-negative bacteria are generally more resistant to antibiotics due to their outer membrane.

Microbial Metabolism

Glycolysis Overview

Glycolysis is the breakdown of glucose to pyruvate, generating ATP and NADH.

• Location: Cytoplasm

• Products: 2 ATP, 2 NADH, 2 pyruvate per glucose

Respiration vs Fermentation

• Respiration: Requires oxygen (aerobic) or other electron acceptors (anaerobic), produces more ATP.

• Fermentation: Occurs without oxygen, produces less ATP, end products include lactic acid or ethanol.

Necessary Conditions: Respiration requires oxygen or alternative electron acceptors; fermentation requires organic substrates.

Energy Sources:

• Chemoheterotrophs: Use organic compounds for energy and carbon.

• Photoautotrophs: Use light for energy, CO2 for carbon.

Microbial Growth

Cardinal Temperatures

Microbes have minimum, optimum, and maximum temperatures for growth.

• Psychrophiles: Grow at low temperatures (0-20°C)

• Mesophiles: Grow at moderate temperatures (20-45°C)

• Thermophiles: Grow at high temperatures (45-80°C)

Biofilms

Biofilms are communities of microbes attached to surfaces, protected by extracellular matrix.

• Importance: Increased resistance to antibiotics and environmental stresses.

Oxygen Requirements

• Obligate Aerobe: Requires oxygen

• Microaerophile: Requires low oxygen

• Facultative Anaerobe: Can grow with or without oxygen

• Obligate Anaerobe: Cannot tolerate oxygen

Bacterial Growth

Bacterial growth is typically measured by increase in cell number, often in four phases: lag, log, stationary, and death.

Control of Microbial Growth

Physical and Chemical Methods

Microbial control involves various methods:

• Physical: Heat (autoclaving, pasteurization), filtration, radiation.

• Chemical: Disinfectants, antiseptics, antibiotics.

Success depends on: Type of microbe, environment, concentration, exposure time.

Microbial Genetics

Structure of DNA and RNA

• DNA: Double helix, deoxyribose sugar, A-T and G-C base pairs.

• RNA: Single-stranded, ribose sugar, A-U and G-C base pairs.

Bacterial vs Human DNA

• Bacterial DNA: Circular, few chromosomes, often contains plasmids.

• Human DNA: Linear, multiple chromosomes, no plasmids.

Enzymes in DNA Replication

• DNA Polymerase: Synthesizes new DNA strands.

• Helicase: Unwinds DNA.

• Ligase: Joins DNA fragments.

Transcription and Translation

• Transcription: DNA → RNA

• Translation: RNA → Protein

• Differences: Prokaryotes can couple transcription and translation; eukaryotes separate them by the nuclear membrane.

Plasmids

Plasmids are small, circular DNA molecules in bacteria, often carrying antibiotic resistance genes.

Genetic Material Transfer

• Transformation: Uptake of naked DNA

• Conjugation: Transfer via pilus

• Transduction: Transfer via bacteriophage

Biotechnology and DNA Technology

Tools of Biotechnology

• Restriction enzymes: Cut DNA at specific sequences.

• Vectors: Carry DNA into host cells.

PCR (Polymerase Chain Reaction)

PCR amplifies DNA sequences using cycles of heating and cooling.

• Steps: Denaturation, annealing, extension.

$\text{PCR Cycle:} \quad \text{Denature} \rightarrow \text{Anneal} \rightarrow \text{Extend}$

Recent Advances

Current research includes CRISPR gene editing and next-generation sequencing.

Microbial Classification

Microbes of Interest

Protozoans, fungi, bacteria, and viruses are frequently discussed in labs and lectures.

Viruses, Viroids, and Prions

Viral Anatomy

• Capsid: Protein coat

• Envelope: Lipid membrane (in some viruses)

• Nucleic Acid: DNA or RNA

Viral Replication Cycles

• Lytic Cycle: Virus replicates and lyses host cell.

• Lysogenic Cycle: Viral DNA integrates into host genome.

• Multiplication of Animal Viruses: Includes attachment, entry, uncoating, replication, assembly, release.

Terminology

• Virulence: Degree of pathogenicity

• Infection: Invasion of host by pathogen

Microbial Mechanisms of Pathogenicity

Portals of Entry and Transmission

• Portals: Skin, mucous membranes, respiratory tract, GI tract

• Transmission: Direct contact, airborne, vector-borne

Virulence Factors

• Capsules: Prevent phagocytosis

• Enzymes: Damage host tissues

Host Cell Damage

• Exotoxins: Secreted proteins, specific effects

• Endotoxins: Lipopolysaccharide from Gram-negative bacteria, general effects

Innate Immunity: Nonspecific Defenses

First Line of Defense

• Physical Barriers: Skin, mucous membranes

• Chemical Factors: Lysozyme, acidic pH

Second Line of Defense

• Cells: Neutrophils, macrophages, dendritic cells

• Inflammation: Response to injury or infection

Phagocytosis Mechanisms

• Steps: Chemotaxis, adherence, ingestion, digestion

Complement System

• Pathways: Classical, alternative, lectin

• Outcomes: Opsonization, inflammation, cell lysis

$\text{Complement Activation:} \quad \text{C3} \rightarrow \text{C3a} + \text{C3b}$

Antimicrobial Substances

• Defensins: Small peptides that disrupt microbial membranes

• Interferons: Inhibit viral replication

Adaptive Immunity: Specific Defenses

Cells of the Third Line of Defense

• B cells: Originate and mature in bone marrow, produce antibodies

• T cells: Originate in bone marrow, mature in thymus, mediate cellular immunity

Innate vs Adaptive Immunity

• Innate: Nonspecific, immediate response

• Adaptive: Specific, memory, slower response

Antibodies

• Structure: Y-shaped, variable and constant regions

• Classes: IgG, IgM, IgA, IgE, IgD

• Functions: Neutralization, opsonization, complement activation

Antigen Presenting Cells (APCs)

• Types: Dendritic cells, macrophages, B cells

• Function: Present antigens to T cells

Types of Adaptive Immunity

• Humoral: Mediated by antibodies

• Cellular: Mediated by T cells

Practical Applications of Immunology

History and Types of Vaccines

• Live attenuated: Strong immunity, risk in immunocompromised

• Inactivated: Safer, weaker immunity

• Subunit: Only parts of pathogen, fewer side effects

Sensitivity and Specificity

• Sensitivity: Ability to detect true positives

• Specificity: Ability to detect true negatives

Monoclonal Antibodies

Used for diagnosis and treatment of diseases.

Agglutination Reactions

• Direct: Antigen and antibody react directly

• Indirect: Uses particles coated with antigen or antibody

ELISA Principles

Enzyme-linked immunosorbent assay detects antigens or antibodies using enzyme-labeled reagents.

Disorders Associated with the Immune System

Types of Hypersensitivities

• Type I: Immediate (allergy)

• Type II: Cytotoxic

• Type III: Immune complex

• Type IV: Delayed (cell-mediated)

Autoimmune Diseases

Immune system attacks self tissues; examples include lupus, rheumatoid arthritis.

Transplantation Complexities

Immune rejection, immunosuppressive therapy, matching MHC antigens.

HIV/AIDS

HIV infects CD4+ T cells, leading to immunodeficiency and increased susceptibility to infections.

Antimicrobial Drugs

Mechanisms of Action

• Inhibition of cell wall synthesis

• Inhibition of protein synthesis

• Inhibition of nucleic acid synthesis

• Disruption of membrane function

Microbial Diseases of Organ Systems

For chapters 21-26, refer to learning objectives and microbe sets for details on diseases of skin, eyes, nervous, cardiovascular, respiratory, digestive, urinary, and reproductive systems.

Summary Table: Microbial Classification

Domain	Cell Type	Cell Wall	Examples
Bacteria	Prokaryote	Peptidoglycan	Escherichia coli
Archaea	Prokaryote	No peptidoglycan	Halobacterium
Eukarya	Eukaryote	Varies (cellulose, chitin, none)	Saccharomyces cerevisiae, Paramecium

Additional info: This guide expands on brief points with academic context, definitions, and examples for comprehensive exam preparation.