Microbiology Chapter 1: History

Microorganisms and Early Scientists

• Microorganisms include bacteria, viruses, fungi, protozoa, and algae; visible only through microscopes.
• Antoni van Leeuwenhoek first observed microorganisms in 1674, coining the term “animalcules.”
• Louis Pasteur disproved spontaneous generation with his swan-neck flask experiment, introducing pasteurization for food preservation.
• Robert Koch formulated Koch’s postulates, linking specific microorganisms to specific diseases, discovering the causative agents of anthrax and tuberculosis.

Understanding Life Origins

• Spontaneous generation was the belief life could arise from non-living materials.
• Biogenesis, the modern theory, states that life arises from pre-existing life.

Atoms, Molecules, and Life's Chemistry

• Atoms, the fundamental units of matter, combine to form molecules; essential elements include carbon, hydrogen, oxygen, and nitrogen.
• Covalent bonds involve electron sharing, while ionic bonds involve electron transfer; hydrogen bonds are crucial in water and proteins.
• Water is vital, characterized by cohesion and its ability to dissolve many substances.

Macromolecules of Life

• Carbohydrates serve as energy sources; proteins are made of amino acids and facilitate cellular functions.
• Lipids store energy, while nucleic acids (DNA and RNA) carry genetic information.
• Enzymes are proteins that catalyze metabolic reactions, essential for life processes.

Cell Structure: Prokaryotes vs. Eukaryotes

• Prokaryotic cells are simple, lacking a nucleus; key components include the cell membrane, cytoplasm, ribosomes, and circular DNA.
• Eukaryotic cells are more complex, featuring a nucleus and organelles; major structures include the nucleus, mitochondria, endoplasmic reticulum, and Golgi apparatus.
• Eukaryotic cells are generally larger and have specialized organelles, unlike prokaryotes.

Microscopy and Microbial Classification

• Light microscopes utilize light for magnification, while electron microscopes employ electrons to visualize finer details, such as viruses.
• Staining techniques include simple stains and the Gram stain, classifying bacteria as Gram-positive (purple, thick cell wall) or Gram-negative (pink, thin cell wall).
• Bacteria are single-celled prokaryotes; archaea resemble bacteria but inhabit extreme environments; viruses are dependent on hosts for reproduction; fungi include yeasts and molds; protozoa are single-celled eukaryotes.

Microbial Metabolism Overview

• Metabolism encompasses all chemical reactions within organisms, categorized into catabolism (energy release) and anabolism (energy consumption).
• ATP (Adenosine Triphosphate) is the primary energy currency for cells, utilized for various cellular functions.
• Enzymatic activity lowers the activation energy for reactions; the active site is where substrate interactions occur.
• Cellular respiration involves glycolysis (glucose breakdown), the Krebs cycle (ATP production), and the electron transport chain (maximum ATP output).

Microbial Nutrition and Growth Conditions

• Essential nutrients for microorganisms include carbon, nitrogen, oxygen, and hydrogen; each requires an optimal temperature range for growth.
• pH preferences vary among microorganisms; most thrive in neutral conditions but some prefer acidic or basic environments.
• Bacterial reproduction occurs via binary fission, dividing one cell into two and progressing through growth phases: lag phase, log phase (rapid growth), stationary phase (resource depletion), and death phase.