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Microbiology Fundamentals

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  • Roles of Microorganisms

    Benefits: Nutrient cycling, food production (fermentation), biotechnology, ecological balance.
    Detriments: Infectious diseases, food spoilage, biofouling.

  • Examples of Beneficial and Harmful Microbes

    Beneficial: Lactobacillus ferments milk to yogurt.
    Harmful: Salmonella causes foodborne illness.

  • Emerging Infectious Diseases

    New or re-emerging infections due to microbial evolution, environment, or human behavior. Examples: SARS, MERS, Zika, antibiotic-resistant bacteria.

  • Pioneers of Microbiology

    Leeuwenhoek: First to observe microbes.
    Pasteur: Disproved spontaneous generation, pasteurization.
    Koch: Germ theory, Koch's postulates.
    Lister: Antiseptic surgery.

  • Viruses vs. Cellular Life Forms

    Viruses are acellular, lack metabolism, need host cells.
    Cellular life (prokaryotes, eukaryotes) have cells and independent metabolism.

  • Prokaryotic vs. Eukaryotic Cells

    Prokaryotes: No nucleus, simple (Bacteria, Archaea).
    Eukaryotes: Nucleus, organelles (Fungi, Protozoa, Algae).

  • Endosymbiotic Theory

    Explains mitochondria and chloroplast origin from ancestral prokaryotes, supported by DNA and ribosome similarities.

  • Prokaryotic External Structures

    Flagella: Motility.
    Pili: Attachment and conjugation.
    Capsules: Protection and adherence.

  • Bacterial Morphologies and Arrangements

    Shapes: Cocci (spherical), Bacilli (rod), Spirilla (spiral).
    Arrangements: Chains (strepto-), clusters (staphylo-), pairs (diplo-).

  • Bacterial Cell Wall Types

    Gram-positive: Thick peptidoglycan, teichoic acids.
    Gram-negative: Thin peptidoglycan, outer membrane with lipopolysaccharide.
    Acid-fast: Mycolic acids.

  • Membrane Transport Processes

    Diffusion, facilitated diffusion, osmosis, active transport, group translocation.

  • Bacterial Endospores

    Dormant, resistant structures formed by Bacillus and Clostridium; survive heat, desiccation, chemicals.

  • Metric Units in Microbiology

    1 mm = 1000 µm; 1 µm = 1000 nm.

  • Principles of Microscopy

    Magnification, resolution, contrast, illumination.

  • Types of Microscopy

    Bright-field, dark-field, phase-contrast, fluorescence, differential interference contrast, electron microscopy (SEM, TEM).

  • Common Staining Procedures

    Simple stain: whole cell.
    Gram stain: Gram+ vs Gram-.
    Acid-fast stain: mycobacteria.
    Endospore stain: detects endospores.

  • Microbial Metabolism: Anabolism vs Catabolism

    Anabolism: Builds complex molecules, requires energy.
    Catabolism: Breaks down molecules, releases energy.

  • ATP Production Methods

    Substrate-level phosphorylation, oxidative phosphorylation, photophosphorylation.

  • Major Metabolic Pathways

    Glycolysis: Glucose to pyruvate.
    Intermediate step: Pyruvate to Acetyl-CoA.
    Krebs cycle: Acetyl-CoA to CO2.
    Electron transport chain: ATP via oxidative phosphorylation.

  • Fermentation

    Occurs without oxygen; regenerates NAD+. Examples: lactic acid fermentation (Lactobacillus), ethanol fermentation (yeast).

  • Oxygen Toxic Forms and Enzymes

    Toxic forms: superoxide radical, hydrogen peroxide, hydroxyl radical.
    Enzymes: superoxide dismutase, catalase, peroxidase.

  • Oxygen Requirements and Growth in Thioglycolate Medium

    Obligate aerobe: top growth.
    Obligate anaerobe: bottom.
    Facultative anaerobe: throughout, mostly top.
    Microaerophile: just below surface.
    Aerotolerant anaerobe: evenly throughout.

  • Physical Factors Affecting Microbial Growth

    Temperature: psychrophiles, mesophiles, thermophiles, hyperthermophiles.
    pH: acidophiles, neutrophiles, alkaliphiles.
    Osmotic pressure: halophiles tolerate high salt.

  • Symbiotic Relationships

    Mutualism: both benefit.
    Commensalism: one benefits, other unaffected.
    Parasitism: one benefits at other's expense.

  • Biofilms

    Microbial communities attached to surfaces; increase resistance to antibiotics and immune responses.

  • Microbial Culture Techniques

    Pure cultures by streak, pour, or spread plate.
    Media types: defined, complex, enriched, selective, differential, anaerobic.

  • Phases of Microbial Growth

    Lag: adaptation, no division.
    Log: rapid division.
    Stationary: growth = death.
    Death: cells die faster than divide.

  • Bacterial Exponential Growth Equation

    \(N_t = N_0 \times 2^n\) where N_t is final cell number, N_0 initial, n number of generations.

  • Generation Time

    Time required for a bacterial population to double in number.

  • Methods to Measure Bacterial Growth

    Direct counts (microscopy, electronic counters), viable plate counts, turbidity (spectrophotometry), serial dilutions.