Microbiology Exam 1 Comprehensive Study Guide

Introduction to Microbiology

Scope of Microbiology

Microbiology is the study of organisms too small to be seen with the naked eye, including both living and nonliving entities.

• Organisms studied: Bacteria, Archaea, Protists, Fungi, Helminths (worms), Viruses, Prions

• Microbes can be pathogenic (disease-causing) or nonpathogenic.

Organization of Life

• Biologists classify living organisms using a taxonomic hierarchy:

• Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species

Ubiquity and Importance of Microorganisms

• Ubiquitous: Microorganisms are found everywhere—soil, water, air, surfaces, and within living organisms.

• Importance:

  • Train the immune system

  • Produce vitamins

  • Aid in digestion

  • Influence mood and brain function

  • Essential for nutrient cycling and environmental balance

Historical Foundations

• Hippocrates: Proposed natural causes for diseases; emphasized observation.

• Spontaneous Generation: The disproven idea that life arises from nonliving matter.

• Key Experiments:

  • Redi: Showed maggots come from flies, not meat.

  • Pasteur: S-neck flask experiment proved biogenesis (life from life).

• Germ Theory of Disease: Microorganisms cause infectious diseases (Koch).

Notable Microbiologists

• Louis Pasteur: Pasteurization, vaccines, disproved spontaneous generation.

• Robert Koch: Staining, culturing, Koch’s Postulates, identified anthrax and TB agents.

• Ignaz Semmelweis: Handwashing, aseptic techniques.

• Joseph Lister: Aseptic surgery, phenol disinfectant.

• Florence Nightingale: Modern nursing, aseptic practices.

• Antonie van Leeuwenhoek: Improved microscopes, first to observe microbes.

• Robert Hooke: Coined “cell,” early microbe observations.

Biochemistry Basics

Atoms, Elements, and Chemical Bonds

• Atom: Smallest unit of matter.

• Element: Type of atom with unique properties.

• Subatomic particles: Protons (+), Neutrons (0), Electrons (−)

• Ions: Charged atoms (cations +, anions −)

• Isotopes: Atoms of the same element with different neutron numbers.

• Molecule: Two or more atoms bonded together.

• Compound: Molecule with more than one element.

Chemical Bonding

• Octet Rule: Atoms gain, lose, or share electrons to achieve 8 in their outer shell.

• Ionic Bonds: Attraction between oppositely charged ions.

• Covalent Bonds: Atoms share electrons.

• Hydrogen Bonds: Weak attractions between polar molecules.

Polarity and Water

• Polar molecules: Unequal electron sharing, partial charges (e.g., water).

• Nonpolar molecules: Equal electron sharing, no significant charges (e.g., fats).

• Hydrophilic: Water-loving, dissolves in water.

• Hydrophobic: Water-fearing, does not dissolve in water.

• Amphipathic: Both hydrophilic and hydrophobic regions (e.g., phospholipids).

Acids, Bases, and pH

• Acid: Donates H+ ions.

• Base: Donates OH− ions.

• pH Scale: Measures H+ concentration; low pH = acidic, high pH = basic.

Organic vs. Inorganic Compounds

• Organic: Contains both carbon and hydrogen.

• Inorganic: May contain carbon or hydrogen, but not both together.

Macromolecules and Their Building Blocks

• Carbohydrates: Monomer = monosaccharide; Polymer = polysaccharide; Bond = glycosidic bond.

• Lipids: Hydrophobic molecules (fats, oils, steroids, phospholipids); energy storage, membranes.

• Nucleic Acids: Monomer = nucleotide; Types = DNA, RNA; Bond = phosphodiester bond.

• Proteins: Monomer = amino acid; Bond = peptide bond.

Polymerization Reactions

• Dehydration synthesis: Forms polymers by removing water.

• Hydrolysis: Breaks polymers by adding water.

Protein Structure

• Primary: Amino acid sequence.

• Secondary: Alpha-helices, beta-sheets (hydrogen bonds).

• Tertiary: 3D shape of a polypeptide.

• Quaternary: Multiple polypeptides combined.

Introduction to Prokaryotic and Eukaryotic Cells

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes: Domains Bacteria and Archaea; no nucleus or membrane-bound organelles.

• Eukaryotes: Domain Eukarya; have nucleus and organelles.

Cell Structures and Functions

• Flagella: Motility; anchored in cell wall.

• Fimbriae: Attachment to surfaces; important for pathogenicity.

• Pili: Attachment, movement, gene transfer (conjugation).

• Glycocalyx: External carbohydrate-rich layer; types: slime layer (loose), capsule (tight); aids in attachment and protection.

Gram-Positive vs. Gram-Negative Bacteria

Feature	Gram-Positive	Gram-Negative
Peptidoglycan Layer	Thick	Thin
Outer Membrane	Absent	Present
Teichoic Acids	Present	Absent
LPS (Endotoxin)	Absent	Present
Stain Color	Purple	Pink

Other Structures

• Cell Membrane: All bacteria have it; described by the fluid mosaic model.

• Chromosome: Main DNA molecule; circular in prokaryotes.

• Plasmid: Small, extra-chromosomal DNA (often antibiotic resistance genes).

• Ribosome: Protein synthesis; prokaryotic ribosome = 70S (50S + 30S).

• Inclusions/Granules: Storage bodies (e.g., carboxysomes, magnetosomes).

• Endospores: Dormant, resistant structures formed under stress (e.g., Clostridium, Bacillus).

Eukaryotic Cell Structures

• Endosymbiotic Theory: Mitochondria and chloroplasts evolved from engulfed prokaryotes.

• Cilia vs. Flagella: Cilia are shorter, more numerous; both aid in movement.

• Nucleus: Contains DNA, nucleolus (ribosome synthesis).

• ER: Rough (protein synthesis), Smooth (lipid synthesis).

• Golgi Apparatus: Modifies, sorts, and ships proteins/lipids.

• Mitochondria: ATP production.

• Chloroplasts: Photosynthesis in plants/algae.

Eukaryotic Microorganisms

• Fungi: Absorb nutrients; can be pathogens or decomposers.

• Protists: Diverse; can be autotrophs (algae) or heterotrophs (protozoans).

• Protozoans: Motile, classified by movement type; some cause disease (e.g., Plasmodium).

• Helminths: Parasitic worms.

Genetics

Genetic Terminology

• Chromosome: DNA molecule with proteins.

• Plasmid: Small, circular DNA.

• Genome: All genetic material in a cell/virus.

• Gene: DNA segment encoding a product.

• Allele: Variant form of a gene.

• Genotype: Genetic makeup.

• Phenotype: Observable traits.

• Histones: DNA-organizing proteins in eukaryotes.

• Intergenic: DNA between genes.

DNA Packaging

• Prokaryotes: One circular chromosome, nucleoid region, histone-like proteins, may have plasmids.

• Eukaryotes: Multiple linear chromosomes, nucleus, histones, DNA in mitochondria/chloroplasts.

DNA and RNA Structure

• Nucleotide: Sugar, phosphate, nitrogenous base.

• DNA: Deoxyribose, thymine, double-stranded, genetic storage.

• RNA: Ribose, uracil, single-stranded, protein synthesis roles.

Central Dogma

• Information flow: DNA → RNA → Protein

• Gene expression involves transcription and translation.

DNA Replication

• Begins at origin of replication.

• Helicase: Unwinds DNA.

• Primase: Lays RNA primers.

• DNA Polymerase III: Synthesizes new DNA (5'→3').

• DNA Polymerase I: Replaces RNA primers with DNA.

• Ligase: Joins Okazaki fragments.

• Gyrase/Topoisomerase: Relieves tension.

• Leading strand: Continuous synthesis.

• Lagging strand: Discontinuous, Okazaki fragments.

Transcription and Translation

• Transcription: DNA → RNA (RNA polymerase).

• mRNA: Carries code; tRNA: Brings amino acids; rRNA: Ribosome structure/function.

• Introns: Noncoding sequences removed in eukaryotes.

• Genetic Code: Triplet codons, redundant, universal.

Viruses and Prions

Viruses

• Definition: Nonliving, obligate intracellular pathogens.

• Structure: Genome (DNA or RNA), capsid (protein coat), sometimes envelope and spikes.

• Capsid: Protein shell; Capsomer: Subunit of capsid.

• Spike: Glycoprotein for host attachment.

• Envelope: Lipid membrane from host cell.

• Genome forms: DNA/RNA, ss/ds, circular/linear, segmented/nonsegmented.

Viral Replication (Animal Viruses)

1. Attachment (adsorption)

2. Penetration (entry)

3. Uncoating

4. Replication (synthesis)

5. Assembly (maturation)

6. Release (budding or lysis)

Cytopathic Effects and Oncogenic Viruses

• Cytopathic effects: Visible host cell changes due to viral infection (e.g., lysis, death).

• Oncoviruses: Can cause cancer by disrupting cell cycle control (e.g., HPV, HTLV).

Bacteriophages

• Lytic Cycle: Immediate replication, host cell lysis.

• Lysogenic Cycle: Viral DNA integrates as prophage, can later enter lytic cycle.

Prions

• Definition: Infectious proteins, no nucleic acids.

• Diseases: Transmissible spongiform encephalopathies (e.g., CJD).

Fundamentals of Microbial Growth

Bacterial Growth and Division

• Binary fission: Main method of division; some use budding or spore formation.

• Generation time: Time for one cell to divide.

• Growth curve phases:

  • Lag

  • Log (Exponential)

  • Stationary

  • Death

• Chemostat: Maintains continuous growth by adding/removing media/cells.

Environmental Factors Affecting Growth

• Temperature: Minimum, maximum, optimum for each species.

• pH: Minimum, maximum, optimum.

• Osmotic conditions: Salt concentration.

• Oxygen requirements:

  • Obligate aerobe: Needs O2

  • Facultative anaerobe: Prefers O2, can live without

  • Obligate anaerobe: Cannot use O2

  • Microaerophile: Low O2

  • Aerotolerant anaerobe: Tolerates O2, does not use

Microbial Classifications by Growth Conditions

Type	Temperature Range	pH Range	Salt Tolerance
Psychrophile	−20°C to 10°C	Varies	Varies
Mesophile	10°C to 50°C	Varies	Varies
Thermophile	40°C to 75°C	Varies	Varies
Extreme Thermophile	65°C to 120°C	Varies	Varies
Acidophile	Varies	1–5	Varies
Neutrophile	Varies	5–8	Varies
Alkaliphile	Varies	9–11	Varies
Halophile	Varies	Varies	Up to 35%

Nutrition and Growth Factors

• Essential nutrients: Required for growth.

• Heterotroph: Needs organic carbon.

• Autotroph: Uses CO2 as carbon source.

• Growth factor: Substance cell cannot synthesize; must be acquired.

• Fastidious: Requires many growth factors.

Energy and Carbon Source Classifications

Type	Energy Source	Carbon Source
Photoautotroph	Light	CO2
Photoheterotroph	Light	Organic compounds
Chemoautotroph	Chemical breakdown	CO2
Chemoheterotroph	Chemical breakdown	Organic compounds

Control of Microbial Growth

Decontamination, Sterilization, and Disinfection

• Decontamination: Reduces/removes microbes to safe levels.

• Sterilization: Destroys all microbes, including endospores.

• Disinfection: Reduces microbial numbers, not all eliminated.

Physical and Chemical Control Methods

• Heat: Autoclaving, boiling, pasteurization.

• Cold: Slows growth (refrigeration, freezing).

• Radiation: Ionizing (X-rays), non-ionizing (UV).

• Filtration: Removes microbes physically.

• Chemical germicides: Disinfectants, antiseptics.

Measuring Microbial Death

• Decimal Reduction Time (DRT): Time to kill 90% at a given temperature.

• Thermal Death Time: Shortest time to kill all at a set temperature.

• Thermal Death Point: Lowest temperature to kill all in 10 minutes.

Germicides and Their Levels

Level	Targets	Examples
Low	Most bacteria (not M. tuberculosis), fungi, some viruses	Detergents
Intermediate	All bacteria (including M. tuberculosis), fungi, viruses	Alcohols, phenols
High	All microbes, endospores	Aldehydes, peroxygens, ethylene oxide

• Microbiocidal: Kills microbes.

• Microbiostatic: Inhibits growth.

• Disinfectant: Used on objects.

• Antiseptic: Used on living tissue.

Medical Equipment Decontamination Tiers

Tier	Contact	Requirement
Critical	Sterile tissues/vascular system	Sterilization
Semicritical	Mucous membranes/nonintact skin	High-level disinfection
Noncritical	Intact skin	Low/intermediate disinfection

Laboratory Safety and Techniques

Containment and Biohazard Safety Levels

• Primary containment: Protects workers.

• Secondary containment: Protects environment.

BSL	Description	Organisms Handled
1	Basic teaching/research	Nonpathogenic
2	Diagnostic/healthcare	Moderate risk
3	Specialized research	Serious/lethal, airborne
4	Maximum containment	Severe/fatal, no cure

Five I’s of Microbiology Lab

• Inoculation: Introducing microbes to media.

• Incubation: Providing growth conditions.

• Isolation: Separating species.

• Inspection: Observing characteristics.

• Identification: Determining species.

Aseptic Technique

• Work near flame, minimize exposure, flame tools, avoid contamination.

• Importance: Prevents contamination, ensures accurate results, prevents infection.

Sterilization Methods

• Autoclaving: Steam under pressure (121°C, 15 psi, 15 min).

• Dry Heat: 160–170°C for 2 hours.

• Filtration: For heat-sensitive materials.

• Radiation: UV, X-rays.

• Chemical sterilization: Bleach, disinfectants.

• Incineration: Flaming loops.

Types of Media

• Solid: Contains agar; allows colony observation.

• Liquid (broth): No agar; for large-scale growth.

Colony Isolation and Streak Plate Technique

• Purpose: Obtain pure cultures from mixed samples.

• Colony: Visible cluster from a single cell.

• Streak Plate: Divide plate, streak with sterilized loop, incubate, observe isolated colonies.

• Pure culture: One species; necessary for identification and testing.

Colony Morphology Terms

• Shape: Circular, irregular, filamentous

• Margin: Entire, undulate, lobate

• Elevation: Flat, raised, convex

• Color, size, texture

Signs of Poor Aseptic Technique

• Unexpected growth in controls, cloudiness, mixed colonies—indicate contamination.

Additional info:

• Some definitions and examples were expanded for clarity and completeness.

• Tables were recreated to summarize comparisons and classifications.

• Where the original notes referenced textbook pages, content was synthesized for self-contained study.