Microbiology Study Notes: Foundations, Chemistry, and Cell Structure

Chapter 1: A Brief History of Microbiology

Introduction to Microbiology

• Microbiology is the study of organisms too small to be seen with the naked eye, including bacteria, viruses, fungi, protozoa, and algae.

• Key historical figures contributed to the development of microbiology as a science.

Early Pioneers

• Antoni van Leeuwenhoek (1632–1723): Dutch tailor and merchant who first observed microorganisms using simple microscopes he constructed himself.

• He described 'animalcules' (microbes) and was the first to look at living samples.

• Carolus Linnaeus: Developed a system for naming and classifying organisms (binomial nomenclature).

Major Groups of Microorganisms

• Bacteria, Archaea, Fungi, Protozoa, Algae, Small multicellular animals, Viruses (not visible by light microscopy).

Golden Age of Microbiology

• Roughly 50 years prior to the late 1800s, driven by four key questions:

  1. Is spontaneous generation possible?

  2. What causes fermentation?

  3. What causes disease?

  4. How can we prevent infection and disease?

Spontaneous Generation Debate

• Spontaneous generation: The hypothesis that living organisms arise from nonliving matter.

• Key experiments:

  • Francesco Redi: Showed that maggots do not arise spontaneously from meat.

  • John Needham: Claimed that boiled broths still produced microorganisms.

  • Lazzaro Spallanzani: Improved Needham's experiments, showing that sealed and boiled broths did not produce life.

  • Louis Pasteur: Used swan-necked flasks to finally disprove spontaneous generation, showing that microbes come from other microbes (biogenesis).

The Scientific Method

• A systematic approach to answering questions through observation, hypothesis, experimentation, and analysis.

Fermentation and Disease

• Fermentation: Conversion of sugars to alcohol, acids, or gases by microorganisms.

• Pasteur's experiments showed that specific microbes cause specific types of fermentation (e.g., yeast for alcohol, bacteria for acid).

• Pasteurization: Heating liquids to kill unwanted microbes.

• Germ Theory of Disease: Diseases are caused by specific microorganisms (pathogens).

Koch's Postulates and Contributions

• Robert Koch: Identified the bacteria causing anthrax and tuberculosis.

• Koch's Postulates (criteria to establish a causative relationship between a microbe and a disease):

  1. The suspected agent must be found in every case of the disease and absent from healthy hosts.

  2. The agent must be isolated and grown outside the host.

  3. When introduced to a healthy host, the agent must cause the disease.

  4. The same agent must be reisolated from the diseased experimental host.

• Developed techniques for isolating and culturing bacteria (e.g., Petri plates, solid media).

• Introduced the Gram stain for bacterial classification.

Prevention of Infection and Disease

• Semmelweis: Handwashing to prevent puerperal fever.

• Joseph Lister: Antiseptic surgery using carbolic acid.

• Florence Nightingale: Hygiene in nursing.

• Edward Jenner: Smallpox vaccination.

• Paul Ehrlich: Chemotherapy (selective toxicity).

• Alexander Fleming: Discovery of penicillin (antibiotics).

Chapter 2: The Chemistry of Microbiology

Basic Chemical Principles

• Atoms, elements, compounds, and molecules are the building blocks of matter.

• Chemical bonds include ionic, covalent, and hydrogen bonds.

• Water is essential for life due to its polarity, hydrogen bonding, and solvent properties.

Water

• Hydrogen bonds hold water molecules together, giving water its unique properties (cohesion, adhesion, high specific heat, solvent abilities).

• Hydrophilic substances dissolve in water; hydrophobic substances do not.

Organic Chemistry: Biological Macromolecules

• Four main types: Carbohydrates, Lipids, Proteins, Nucleic Acids.

• Macromolecules are polymers made from monomers via dehydration synthesis; broken down by hydrolysis.

Carbohydrates

• Composed of C, H, O (general formula: (CH2O)n).

• Monosaccharides (simple sugars), disaccharides, polysaccharides (e.g., glycogen, cellulose).

Lipids

• Composed of C, H, O; hydrophobic.

• Types: Fats (triglycerides), phospholipids (membranes), steroids (hormones, membrane structure), waxes.

Proteins

• Composed of C, H, O, N, S; polymers of amino acids linked by peptide bonds.

• Levels of structure: primary, secondary, tertiary, quaternary.

• Functions: enzymes, transport, structure, signaling.

Nucleic Acids

• Composed of C, H, O, N, P; polymers of nucleotides.

• DNA and RNA store and transfer genetic information.

• ATP is a nucleotide used for cellular energy.

Macromolecule	Monomer	Bond	Function
Carbohydrate	Monosaccharide	Glycosidic	Energy, structure
Lipid	Fatty acid, glycerol	Ester	Membranes, energy storage
Protein	Amino acid	Peptide	Enzymes, structure
Nucleic Acid	Nucleotide	Phosphodiester	Genetic info

Chapter 3: Cell Structure and Function

Characteristics of Living Things

• Growth, reproduction, responsiveness, metabolism, cellular structure.

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

Cell Types: Prokaryotes vs. Eukaryotes

• Prokaryotes: No nucleus, simple structure (e.g., Bacteria, Archaea).

• Eukaryotes: Nucleus, complex organelles (e.g., Fungi, Protozoa, Algae, Animals, Plants).

Bacterial Cell Structure

• Shapes: Cocci (spheres), Bacilli (rods), Spirilla (spirals).

• Arrangements: Chains, clusters, pairs.

• External structures: Glycocalyces (capsules, slime layers), flagella (motility), fimbriae and pili (attachment, conjugation).

• Cell wall: Peptidoglycan (Gram-positive: thick, Gram-negative: thin + outer membrane).

• Cell membrane: Phospholipid bilayer, selective barrier, transport proteins.

• Internal structures: Cytoplasm, ribosomes (protein synthesis), inclusions (storage), endospores (survival), cytoskeleton.

Archaeal Cell Structure

• Similar to bacteria but with unique membrane lipids and cell wall components (no peptidoglycan).

• Can have unusual shapes and external structures (e.g., hami).

Eukaryotic Cell Structure

• External structures: Glycocalyx (if present), cell wall (plants, fungi, algae), plasma membrane.

• Membrane-bound organelles: Nucleus (DNA storage), endoplasmic reticulum (protein/lipid synthesis), Golgi apparatus (modification/transport), lysosomes/peroxisomes (digestion), mitochondria (ATP production), chloroplasts (photosynthesis in plants/algae).

• Motility: Flagella (complex, whip-like), cilia (short, numerous).

• Cytoskeleton: Microtubules, microfilaments, intermediate filaments.

Endosymbiotic Theory

• Explains the origin of mitochondria and chloroplasts as formerly free-living prokaryotes engulfed by ancestral eukaryotic cells.

• Evidence: Double membranes, own DNA, ribosomes similar to bacteria.