Microbial History: People and Concepts

Microbial History: Key People

• Anton van Leeuwenhoek was the first to observe microorganisms with a microscope.
• Louis Pasteur demonstrated that microorganisms cause fermentation and disease and he disproved spontaneous generation.
• Robert Koch developed Koch's postulates used to identify disease causative agents.
• Edward Jenner developed the first smallpox vaccine.
• Joseph Lister was a pioneer in antiseptic surgery who promoted sterilization to prevent infection.

The Golden Age of Microbiology

• Spontaneous generation: life arises from non-living matter, disproven by Pasteur.
• Fermentation is a process where yeast converts sugars to alcohol, microorganisms are responsible.
• Lister promoted sterilization and cleanliness to prevent infection.
• Infectious diseases/germ theory: diseases are caused by microorganisms, established by Pasteur and Koch.

Classification and Nomanclature

• Scientific names are in the format Genus species (e.g. Homo sapiens), Genus is capitalized, species is lowercase, and both are italicized or underlined.
• Linnaeus developed binomial nomenclature, using two Latin names to name organisms.
• The order for hierarchy of classification is Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.

The Three Domains of Life

• The three domains are Bacteria, Archaea, and Eukarya (includes plants, animals, fungi, and protists).

Cell Types

• Eukaryotic cells have a nucleus, such as animal and plant cells.
• Prokaryotic cells do not have a nucleus, such as bacteria and archaea.

Microbe Classifications

• Bacteria are prokaryotic, unicellular organisms.
• Archaea are prokaryotic, distinct from bacteria, and often found in extreme environments.
• Acellular microbes include viruses
• Eukaryotic microbes include fungi, protozoa, and algae.

Chemistry: Atoms, Isotopes, and Ions

• An atom is the basic unit of matter consisting of protons, neutrons, and electrons.
• Isotopes are atoms of the same element with different numbers of neutrons. Examples: Carbon-12, Carbon-14.
• Ions are charged atoms formed by gaining or losing electrons. Examples: Na+, Cl-.

Subatomic Particles: Charge

• Protons are positively charged.
• Neutrons have no charge.
• Electrons are negatively charged.

Types of Bonds

• Ionic bonds are formed when one atom transfers an electron to another, resulting in positively and negatively charged ions (e.g., NaCl).
• Covalent bonds: Atoms share electrons.
• Non-polar covalent bonds: Electrons are shared equally (e.g., O₂).
• Polar covalent bonds: Electrons are shared unequally (e.g., H₂O).

Acids, Bases, and Electrolytes

• Acids release H⁺ ions (e.g., HCl).
• Bases release OH⁻ ions or absorb H⁺ ions (e.g., NaOH).
• Electrolytes are substances that dissociate into ions in water (e.g., salts).

Organic Macromolecules: Lipids

• Monomers of lipids include fatty acids and glycerol.
• Lipids functions include energy storage, forming cell membranes (phospholipids), and insulation.

Organic Macromolecules: Proteins

• Monomer: Amino acids.
• Functions: Catalysis (enzymes), structure, transport, and communication.

Organic Macromolecules: Carbohydrates

• Monomer: Monosaccharides (e.g., glucose).
• Functions: Energy source and cell structure (e.g., cellulose in plants).

Organic Macromolecules: Nucleic Acids

• DNA stores genetic information.
• RNA translates genetic information into proteins.

Growth Media Types

• Solid media is agar-based and provides a solid surface for bacterial growth.
• Liquid media is broth used for growing bacteria in liquid form.

Agar Properties

• Agar is derived from red algae.
• Agar solidifies at a temperature that does not kill most microbes and provides a surface for bacterial growth.

Magnification, Resolution, and Contrast

• Magnification is the enlargement of an image.
• Resolution is the ability to distinguish two objects as separate.
• Contrast is the difference in light intensity between an object and its background.

Types of Light Microscopy

• Bright-field Microscopy: Light passes directly through the sample.
• Dark-field Microscopy: A special condenser makes the background dark, so light specimens appear bright.
• Phase-contrast Microscopy: Enhances contrast in transparent samples by exploiting differences in refractive index.

Differences in Microscopy

• Light Microscopy: Uses visible light with limited resolution (~200 nm).
• Electron Microscopy: Uses electron beams with much higher resolution (up to 0.1 nm).
• Probe Microscopy: Uses a scanning probe to analyze surfaces at the atomic level (e.g., Scanning Tunneling Microscopy).

Purpose of Staining

• Staining enhances contrast, making cells more visible under the microscope.

Challenges of Electron Microscopy

• Requires samples to be in a vacuum, which can alter their structure.
• Samples need to be thinly sliced, which can damage them.
• Requires heavy metal stains, which can be toxic to living cells.