General Microbiology - MCB 201

General Microbiology - MCB 201

• Microbiology is the study of microorganisms, which are organisms too small to be seen with the naked eye.
• Key groups of microorganisms include bacteria, algae, fungi, protozoa, and viruses. Smaller groups also exist, such as prions and viroids.
• Microorganisms are all very small.
• Some microbes, such as bread molds and filamentous algae, can be seen without magnification.
• The study of microbiology is important in many fields, impacting human health, agriculture and industry.

Scope & History of Microbiology

• Microbiology applies the scientific method: observations (objective vs. subjective), formulating hypotheses, testing hypotheses through controlled experiments, and accepting, revising, or rejecting hypotheses.
• Anton van Leeuwenhoek (1632-1723) developed a simple microscope, observed live microorganisms and reported microorganisms at high magnification, and is considered the "father of Microbiology".
• Robert Hooke (1635-1703) built a compound light microscope, observed cork cells, and coined the term "cell". His discovery led to the cell theory, which established that cells are the fundamental units of living organisms.
• Louis Pasteur (1822-1895) demonstrated that infectious diseases are caused by microbes, disproved spontaneous generation, developed the process of pasteurization, and developed vaccines for several diseases in animals and humans.
• Robert Koch (1843–1910) established that microbes cause disease. He developed criteria for linking a microbe to a disease, known as Koch's postulates.

Koch's Postulates

• The microorganism must be present in every case of the disease and absent from healthy organisms.
• The suspected microorganism must be isolated and grown in pure culture.
• When the microorganism is inoculated into a healthy host, the same disease condition must result.
• The same microorganism must be re-isolated from the experimentally infected host.

Why Study Microbiology?

• Impact on human health: microbes are a food source, help in decomposition, and aid other animals in digestion.
• Environmental benefits: providing safe drinking water, developing biodegradable products, cleaning up oil spills (bioremediation).
• Industrial purposes: food production (cheese, bread, wine), antibiotics, insulin, and genetic engineering.
• Agricultural benefits: healthier livestock and disease-free crops.

Important and Beneficial Biological Functions of Microbes

• Food industry: many foods and beverages (e.g., beer, bread, yogurt) are produced using microbes.
• Genetic engineering: microbes are used to produce important products like human growth hormone, insulin, clotting factors for various medical conditions, and antibodies for disease diagnosis and prevention.

Medical Research

• Microbes are well suited for biological and medical research: simple structures, easy study, easily manipulated genetic material, rapid growth, and short generation times for studying genetic changes.
• Many antibiotics and other drugs are synthesized by microbes.

Microbiology Disciplines

• Basic research
  • Microbe-centered disciplines: bacteriology (bacteria and archaea), phycology (algae), mycology (fungi), protozoology (protozoa), parasitology (parasitic protozoa and animals), virology (viruses).
• Process-centered disciplines: microbial metabolism (biochemistry), microbial genetics, environmental microbiology (relationships between microbes and other organisms and their environment).

Microbe Functions

• Digestion: animals have microbes in their digestive tracts for digestion, vitamin synthesis, and overall health.
  • cellulose digestion (e.g. in termites)
  • Vitamin K and B synthesis.
• Photosynthesis: algae and some bacteria capture energy from sunlight and convert it to food.
• Decomposers: break down dead and decaying matter, and recycle nutrients.
• Nitrogen Fixation: bacteria take nitrogen from air and incorporate it into the soil.