Microbiology Exam 1 Study Guide: Chapters 1, 3, 4, 6, 7

Ch. 1 – The Microbial World and You

1.1 The Impact of Microbes on Human Life

• Destructive Actions: Microbes can cause diseases (pathogens), spoil food, and contribute to the deterioration of materials.

• Beneficial Actions: Microbes are essential for nutrient cycling, food production (e.g., cheese, yogurt), bioremediation, and the synthesis of antibiotics and vitamins.

• Example: Lactobacillus species ferment milk to produce yogurt.

1.2 Scientific Nomenclature

• Binomial Nomenclature: Each organism is given a two-part name: the genus (capitalized) and the specific epithet (lowercase), both italicized or underlined (e.g., Escherichia coli).

• Genus vs. Specific Epithet: The genus is a group of related species; the specific epithet identifies the species within the genus.

1.3 Major Groups of Microorganisms

• Prokaryotes: Bacteria and Archaea (lack a nucleus).

• Eukaryotes: Fungi, Protozoa, Algae, and Helminths (have a nucleus).

• Viruses: Acellular, require a host cell to replicate.

1.4 The Three Domains of Life

• Bacteria

• Archaea

• Eukarya

1.5 Historical Contributions

• Hooke: First to observe cells; contributed to cell theory.

• van Leeuwenhoek: First to observe live microorganisms.

• Cell Theory: All living things are composed of cells.

1.6 Spontaneous Generation vs. Biogenesis

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

• Biogenesis: The hypothesis that living cells arise only from preexisting living cells.

• Evidence: Experiments by Redi, Spallanzani, and Pasteur disproved spontaneous generation.

1.7 Key Figures in Microbiology

• Needham: Supported spontaneous generation with broth experiments.

• Spallanzani: Disproved Needham by boiling broth longer and sealing flasks.

• Virchow: Proposed biogenesis.

• Pasteur: Swan-neck flask experiment; disproved spontaneous generation.

1.8 Germ Theory of Disease

• Pasteur: Showed microbes cause fermentation and spoilage.

• Lister: Applied antiseptics in surgery.

• Koch: Developed Koch's postulates to link microbes to disease.

1.9 Koch’s Postulates

• Set of criteria to prove a specific microbe causes a specific disease.

1.10 Jenner’s Discovery

• Developed the first vaccine (smallpox) using cowpox virus.

1.11 Ehrlich and Fleming

• Ehrlich: Developed the first synthetic antimicrobial drug (“magic bullet” for syphilis).

• Fleming: Discovered penicillin.

1.12 Branches of Microbiology

• Bacteriology: Study of bacteria.

• Mycology: Study of fungi.

• Parasitology: Study of parasites.

• Immunology: Study of the immune system.

• Virology: Study of viruses.

1.13 Microbial Genetics and Molecular Biology

• Microbial Genetics: Study of how microbes inherit traits.

• Molecular Biology: Study of how genetic information is carried in DNA and how it directs protein synthesis.

1.14 Beneficial Activities of Microorganisms

• Decomposition, nitrogen fixation, sewage treatment, food production.

1.15 Biotechnology and Recombinant DNA Technology

• Biotechnology: Use of microbes to produce foods and chemicals.

• Recombinant DNA Technology: Insertion of genes into microbes to produce desired products (e.g., insulin, growth hormone).

1.16 Normal Microbiota and Resistance

• Normal Microbiota: Microbes normally present in and on the human body.

• Resistance: Ability to ward off disease.

1.17 Biofilms

• Complex communities of microbes attached to surfaces; important in infections and industrial settings.

1.18 Emerging Infectious Diseases

• New or changing diseases increasing in incidence.

• Contributing Factors: Evolution, antibiotic resistance, global travel, ecological changes.

Ch. 3 – Observing Microorganisms Through a Microscope

3.1 Metric Units of Measurement

• Micrometer (μm): 1 μm = 10-6 m

• Nanometer (nm): 1 nm = 10-9 m

• Conversion: 10 μm = 10,000 nm

3.2 Path of Light in a Compound Microscope

• Light passes through the specimen, objective lens, and ocular lens to the eye.

3.3 Magnification and Resolution

• Total Magnification: Product of objective and ocular lens magnifications.

• Resolution: Ability to distinguish two points as separate; a resolution of 0.2 nm means two points closer than 0.2 nm appear as one.

3.4 Types of Microscopy

• Brightfield: Standard light microscopy.

• Darkfield: Enhances contrast in unstained samples.

• Phase-Contrast: Visualizes internal structures in living cells.

• Differential Interference Contrast (DIC): 3D-like images.

• Fluorescence: Uses fluorescent dyes; detects specific structures.

• Confocal: 3D images using lasers.

• Two-Photon: Deep tissue imaging.

• Scanning Acoustic: Uses sound waves for imaging.

3.5 Electron Microscopy

• Transmission Electron Microscope (TEM): Internal structures, high resolution.

• Scanning Electron Microscope (SEM): Surface details, 3D images.

• Scanned-Probe Microscopy: Surface at atomic level.

• Reason for Higher Resolution: Electrons have shorter wavelengths than light.

3.6 Staining Techniques

• Acidic Dyes: Stain background (negative staining).

• Basic Dyes: Stain cells.

• Simple Staining: Highlights entire organism.

• Fixing: Preserves and attaches cells to slide.

3.7 Differential Stains

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

• Acid-Fast Stain: Identifies Mycobacterium and Nocardia.

3.8 Special Stains

• Capsule Stain: Visualizes capsules.

• Endospore Stain: Detects endospores (appear green when stained).

• Flagella Stain: Visualizes flagella.

Ch. 4 – Functional Anatomy of Prokaryotic and Eukaryotic Cells

4.1 Prokaryotic vs. Eukaryotic Cells

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

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

4.2 Bacterial Shapes

• Coccus: Spherical

• Bacillus: Rod-shaped

• Spiral: Twisted

• Streptococci: Chains of cocci

4.3 Glycocalyx

• Structure: Gelatinous outer covering (capsule or slime layer).

• Function: Protection, attachment, evasion of immune system.

• Medical Importance: Capsules increase virulence (e.g., Streptococcus pneumoniae).

4.4 Surface Structures

• Flagella: Motility.

• Axial Filaments: Motility in spirochetes.

• Fimbriae: Attachment.

• Pili: DNA transfer (conjugation).

4.5 Cell Walls

• Gram-Positive: Thick peptidoglycan, teichoic acids.

• Gram-Negative: Thin peptidoglycan, outer membrane, lipopolysaccharide (LPS).

• Acid-Fast: Mycolic acid layer (e.g., Mycobacterium).

• Archaea: Pseudomurein or no cell wall.

• Mycoplasmas: No cell wall; sterols in membrane.

4.6 Protoplasts, Spheroplasts, and L Forms

• Protoplast: Gram-positive cell without cell wall.

• Spheroplast: Gram-negative cell with partial cell wall removal.

• L Form: Bacteria that have lost their cell wall naturally or artificially.

4.7 Plasma Membrane

• Structure: Phospholipid bilayer with proteins.

• Function: Selective permeability, energy generation.

• Agents Causing Injury: Alcohols, detergents, antibiotics (e.g., polymyxins).

4.8 Transport Mechanisms

• Simple Diffusion: Movement from high to low concentration.

• Facilitated Diffusion: Uses transport proteins.

• Osmosis: Diffusion of water.

• Active Transport: Requires energy (ATP).

• Group Translocation: Substance chemically modified during transport.

4.9 Internal Structures

• Nucleoid: Region containing DNA.

• Ribosomes: Protein synthesis (70S in prokaryotes, 80S in eukaryotes).

• Inclusions: Storage granules (e.g., polysaccharides, lipids, sulfur).

4.10 Endospores

• Function: Survival under harsh conditions.

• Sporulation: Formation of endospores.

• Germination: Return to vegetative state.

4.11 Eukaryotic Cell Structures

• Flagella and Cilia: Motility; structurally different from prokaryotic flagella.

• Cell Walls: Present in plants, fungi, algae; absent in animals.

• Plasma Membrane: Contains sterols.

• Cytoplasm: Contains cytoskeleton and organelles.

• Ribosomes: 80S (cytoplasm), 70S (mitochondria, chloroplasts).

Ch. 6 – Microbial Growth

6.1 Temperature Groups

• Psychrophiles: Cold-loving.

• Mesophiles: Moderate temperature.

• Thermophiles: Heat-loving.

• Hyperthermophiles: Very high temperatures (e.g., deep-sea vents).

6.2 pH and Growth

• Most bacteria grow best at pH 6.5–7.5.

• Buffers: Phosphate salts maintain pH stability.

6.3 Osmotic Pressure

• High salt or sugar concentrations inhibit growth (used in food preservation).

6.4 Chemical Requirements

• Carbon: Structural backbone.

• Nitrogen: Proteins, nucleic acids.

• Sulfur: Amino acids, vitamins.

• Phosphorus: Nucleic acids, ATP.

6.5 Oxygen Requirements

• Obligate Aerobes: Require oxygen.

• Facultative Anaerobes: Grow with or without oxygen.

• Obligate Anaerobes: Cannot tolerate oxygen.

• Aerotolerant Anaerobes: Tolerate but do not use oxygen.

• Microaerophiles: Require low oxygen.

6.6 Toxic Oxygen

• Enzymes like superoxide dismutase and catalase protect aerobes from toxic oxygen forms.

6.7 Biofilms

• Microbial communities attached to surfaces; resistant to antibiotics and immune responses.

6.8 Culture Media

• Chemically Defined: Exact composition known.

• Complex Media: Contains extracts, composition varies.

6.9 Special Culture Techniques

• Anaerobic Techniques: Remove oxygen.

• Living Host Cells: For obligate intracellular microbes (e.g., viruses).

• Candle Jars: Create low-oxygen, high-CO2 conditions.

• Selective Media: Suppress unwanted microbes.

• Differential Media: Distinguish between microbes.

• Enrichment Media: Enhance growth of desired microbes.

6.10 Biosafety Levels

BSL	Description
1	No special precautions; basic teaching labs
2	Moderate risk; lab coat, gloves, eye protection
3	Biosafety cabinets to prevent airborne transmission
4	Sealed, negative pressure; "hot zone"

6.11 Colonies and Pure Cultures

• Colony: Visible mass of microbial cells from a single cell.

• Streak Plate Method: Isolates pure cultures.

6.12 Preservation of Microbes

• Deep-Freezing: -50°C to -95°C.

• Lyophilization: Freeze-drying for long-term storage.

6.13 Bacterial Growth and Division

• Binary Fission: Most common method; cell divides into two.

6.14 Phases of Microbial Growth

Phase	Description
Lag	Adaptation, no division
Log	Exponential growth
Stationary	Growth rate = death rate
Death	Cells die faster than they divide

6.15 Measuring Microbial Growth

• Direct Methods: Plate counts, filtration, MPN, direct microscopic count.

• Indirect Methods: Turbidity, metabolic activity, dry weight.

Ch. 7 – The Control of Microbial Growth

7.1 Key Terms in Microbial Control

• Sterilization: Removal of all microbial life.

• Disinfection: Destruction of pathogens on inanimate objects.

• Antisepsis: Destruction of pathogens on living tissue.

• Degerming: Mechanical removal of microbes.

• Sanitization: Lowering microbial counts to safe levels.

• Biocide/Germicide: Kills microbes.

• Bacteriostasis: Inhibits, but does not kill, microbes.

• Asepsis: Absence of contamination.

7.2 Patterns of Microbial Death

• Microbial death occurs at a constant rate; larger populations take longer to sterilize.

7.3 Effects of Control Agents

• Damage to cell wall, plasma membrane, proteins, or nucleic acids can kill or inhibit microbes.

• Chemicals affecting plasma membranes may also harm human cells.

7.4 Physical Methods of Control

• Moist Heat: Boiling, autoclaving, pasteurization.

• Dry Heat: Flaming, incineration, hot-air sterilization.

• Filtration: Removes microbes from liquids or air.

• Low Temperatures: Inhibit growth.

• High Pressure: Denatures proteins.

• Desiccation: Prevents metabolism.

• Osmotic Pressure: Causes plasmolysis.

7.5 Radiation

• Ionizing Radiation: Damages DNA, produces hydroxyl radicals.

• Nonionizing Radiation: Damages DNA (e.g., UV light).

7.6 Chemical Methods of Control

• Disinfectants: Phenolics, halogens, alcohols, heavy metals, surfactants, aldehydes, peroxygens.

• Halogens: Iodine (antiseptic), chlorine (disinfectant).

• Alcohols: Effective against bacteria and enveloped viruses.

• Surface-Active Agents: Soaps, detergents; useful in food industry.

• Glutaraldehyde: Effective sporicide.

• Chemical Sterilizers: Ethylene oxide, plasma, peracetic acid.

7.7 Factors Affecting Disinfection

• Concentration, organic matter, pH, time, type of microbe.

7.8 Microbial Resistance

• Endospores and gram-negative bacteria are more resistant to biocides than gram-positive bacteria.