BIO 226 Final Exam Study Guide: Microbiology Core Concepts

Microbial World and You

Scientific/Binomial Nomenclature

Binomial nomenclature is the formal system of naming species using two names: the genus and the species. This system ensures clarity and universal understanding in scientific communication.

• Genus: The first part of the name, always capitalized (e.g., Escherichia).

• Species: The second part, not capitalized (e.g., coli).

• Example: Escherichia coli (E. coli)

Key Definitions

• Pathogen: A microorganism that causes disease.

• Microbiota: The community of microorganisms living in a particular environment, such as the human body.

• Microbe: A microscopic organism, including bacteria, viruses, fungi, and protozoa.

• Antibiotics: Substances that inhibit the growth of or kill bacteria.

• Virus: An acellular infectious agent that requires a host cell to replicate.

Organisms Studied in Microbiology

• Bacteria: Prokaryotic, unicellular, diverse metabolic capabilities.

• Viruses: Acellular, require host cells, consist of genetic material and protein coat.

• Fungi: Eukaryotic, includes molds and yeasts, decomposers.

• Protozoa: Eukaryotic, unicellular, often motile.

Prokaryotic vs. Eukaryotic Cells

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

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

Classification System

• Three Domains: Bacteria, Archaea, Eukarya.

• Kingdoms: Further classification within domains.

Observing Microorganisms Through a Microscope

Compound Light Microscope

The compound light microscope is a fundamental tool for observing microorganisms. It uses multiple lenses to magnify specimens.

• Parts: Ocular lens (eyepiece), objective lenses, stage, condenser, light source, coarse and fine focus.

• Function: Magnifies and resolves small objects.

Staining Techniques

• Simple Stain: Uses one dye to highlight cells.

• Differential Stain: Distinguishes between cell types (e.g., Gram stain).

• Gram Stain: Differentiates bacteria into Gram-positive (purple) and Gram-negative (pink).

Functional Anatomy of Prokaryotic & Eukaryotic Cells

Cell Structure and Function

• Flagella: Motility structures.

• Ribosomes: Protein synthesis; prokaryotic (70S), eukaryotic (80S).

• Cytoplasm: Gel-like substance inside cells.

• Nucleus: Contains genetic material (eukaryotes only).

• Capsule: Protective layer outside cell wall.

Cell Wall Composition

• Gram-Positive: Thick peptidoglycan layer.

• Gram-Negative: Thin peptidoglycan, outer membrane.

Morphology Basics

• Coccus: Spherical bacteria.

• Bacillus: Rod-shaped bacteria.

• Streptococcus: Chains of cocci.

• Streptobacilli: Chains of bacilli.

Differences Among Microbial Groups

• Bacteria: Prokaryotic, cell wall with peptidoglycan.

• Fungi: Eukaryotic, cell wall with chitin.

• Viruses: Acellular, no cell wall.

• Protozoa: Eukaryotic, no cell wall.

Microbial Growth

Media Types

• MAC (MacConkey Agar): Selects for Gram-negative bacteria, differentiates lactose fermenters.

• MSA (Mannitol Salt Agar): Selects for staphylococci, differentiates mannitol fermenters.

• EMB (Eosin Methylene Blue Agar): Selects for Gram-negative, differentiates lactose fermenters.

Oxygen Requirements

• Strict Aerobe: Requires oxygen.

• Microaerophile: Requires low oxygen.

• Facultative Anaerobe: Can grow with or without oxygen.

• Strict Anaerobe: Cannot tolerate oxygen.

Streaking and Identification

• Streak Plate Method: Used to isolate pure colonies.

• Identification on MAC: Lactose fermenters appear pink/red.

Binary Fission and Biofilm

• Binary Fission: Asexual reproduction in bacteria.

• Biofilm: Community of microorganisms attached to a surface.

Viruses

General Characteristics

• Obligate intracellular parasites.

• Bacteriophages: Viruses that infect bacteria.

Virus Structure

• Capsid: Protein coat.

• Envelope: Lipid membrane (some viruses).

• Nucleic Acid: DNA or RNA.

Virus Life Cycle

• Lytic Cycle: Virus replicates and lyses host cell.

• Lysogenic Cycle: Viral DNA integrates into host genome.

Eukaryotes: Fungi, Protozoa, Arthropods, Helminths

Fungi

• Characteristics: Eukaryotic, cell wall with chitin, decomposers.

• Mold vs. Yeast: Molds are multicellular, yeasts are unicellular.

• Types of Mycosis: Systemic (deep), cutaneous (skin), superficial (surface).

Protozoa

• Characteristics: Unicellular, eukaryotic, often motile.

Arthropods

• Characteristics: Invertebrates with exoskeleton, segmented bodies.

Helminths

• Characteristics: Multicellular, parasitic worms.

Control of Microbial Growth

Physical Methods

• Heat: Pasteurization, autoclaving.

• Filtration: Removes microbes from liquids.

• Radiation: Damages microbial DNA.

Chemical Methods

• Disinfectants: Used on surfaces.

• Antiseptics: Used on living tissue.

• Organic Acids: Food preservation.

Antimicrobial Drugs

Targets of Drugs

• Antibiotics: Target bacteria.

• Antifungals: Target fungi.

• Antivirals: Target viruses.

Spectrum of Activity

• Narrow Spectrum: Effective against specific organisms.

• Broad Spectrum: Effective against a wide range.

Antibiotic Resistance

• Definition: The ability of microbes to withstand drugs.

Microbial Genetics

Key Terms

• Genome: All genetic material in an organism.

• Chromosome: DNA molecule containing genes.

• Gene: Segment of DNA coding for a product.

DNA Basics

• Nucleotide: Building block of DNA.

• Semiconservative Replication: Each new DNA has one old and one new strand.

• Antiparallel: DNA strands run in opposite directions.

• Shape: Double helix.

Transcription, Translation, Mutation

• Transcription: DNA to RNA.

• Translation: RNA to protein.

• Mutation: Change in DNA sequence.

Classification of Microorganisms

Binomial Nomenclature

• See above for details.

Gram Staining Basics

• See above for details.

Antibodies vs. Antigen

• Antigen: Substance that triggers immune response.

• Antibody: Protein produced by B cells to bind antigens.

Principles of Disease and Epidemiology

Key Definitions

• Colonization: Establishment of microbes in a host.

• Microbiota: See above.

• Virulence: Degree of pathogenicity.

• Pathogen: See above.

• Bacteremia: Presence of bacteria in blood.

• Endemic: Constant presence in a population.

• Pandemic: Worldwide outbreak.

• Epidemic: Sudden increase in cases.

• Epidemiology: Study of disease patterns.

Acute vs. Chronic Infections

• Acute: Rapid onset, short duration.

• Chronic: Slow onset, long duration.

Signs, Symptoms, Syndromes

• Sign: Objective evidence of disease.

• Symptom: Subjective experience.

• Syndrome: Group of signs and symptoms.

Stages of Infectious Disease

• Incubation: Time between exposure and symptoms.

• Prodromal: Early, mild symptoms.

• Illness: Most severe symptoms.

• Decline: Symptoms decrease.

• Convalescence: Recovery period.

Microbial Mechanisms of Pathogenicity

LD50 vs. ID50

• LD50: Dose lethal to 50% of population.

• ID50: Dose infective to 50% of population.

Exotoxins and Endotoxins

• Exotoxins: Secreted proteins, highly toxic.

• Endotoxins: Lipid A of Gram-negative bacteria, released on cell death.

Capsules

• Capsule: Protects bacteria from phagocytosis.

Innate Immunity

Innate vs. Adaptive Immunity

• Innate: Non-specific, immediate response.

• Adaptive: Specific, slower, memory response.

First and Second Line Defenses

• First Line: Skin, mucous membranes.

• Second Line: Phagocytes, inflammation, fever.

Key Terms

• Antigen: See above.

• Inflammation: Response to injury/infection.

• Fever: Elevated body temperature.

Adaptive Immunity

B Cells vs. T Cells

• B Cells: Produce antibodies (humoral immunity).

• T Cells: Mediate cellular immunity.

Cell-Mediated vs. Humoral Immunity

• Cell-Mediated: T cells attack infected cells.

• Humoral: B cells produce antibodies.

Types of T Cells

• Helper T Cells (CD4+): Activate other immune cells.

• Cytotoxic T Cells (CD8+): Kill infected cells.

• Regulatory T Cells: Suppress immune response.

Antibody and Epitope

• Antibody: Protein that binds antigens; produced by B cells.

• Epitope: Specific region of antigen recognized by antibody.

Antibody Structure

• Y-shaped molecule with variable and constant regions.

Primary vs. Secondary Immune Response

• Primary: First exposure, slower, less antibody.

• Secondary: Subsequent exposure, faster, more antibody.

Disorders of the Immune System

Key Definitions

• Autoimmune Disease: Immune system attacks self.

• Immunodeficiency Disease: Impaired immune response.

Diseases of Various Body Systems

Overview

Microbial diseases affect various body systems, including skin, eyes, nervous, cardiovascular, respiratory, digestive, urinary, and reproductive systems. Study outlines from chapters 21-26 for detailed information.

Summary Table: Microbial Groups and Key Features

Group	Cell Type	Cell Wall	Reproduction	Example
Bacteria	Prokaryotic	Peptidoglycan	Binary fission	Escherichia coli
Fungi	Eukaryotic	Chitin	Spore formation	Aspergillus
Protozoa	Eukaryotic	None	Asexual/sexual	Amoeba
Viruses	Acellular	None	Host-dependent	Influenza virus
Helminths	Eukaryotic	None	Sexual	Ascaris

Summary Table: Gram Stain Differences

Type	Peptidoglycan Layer	Outer Membrane	Stain Color
Gram-Positive	Thick	No	Purple
Gram-Negative	Thin	Yes	Pink

Key Equations

Semiconservative DNA Replication

Each new DNA molecule consists of one old strand and one new strand.

$\text{DNA}_{\text{parent}} \rightarrow \text{DNA}_{\text{daughter}} = \text{old strand} + \text{new strand}$

Binary Fission Growth Equation

Population doubling:

$N = N_0 \times 2^n$

Where N is the final number of cells, N0 is the initial number, and n is the number of generations.

Additional info: These notes expand on brief study guide points to provide context and definitions for exam preparation. For detailed disease outlines, refer to chapters 21-26 as instructed.