Introduction to Microbiology

Introduction to Microbiology

• Microbiology is the study of microbes, which are extremely small living organisms and certain non-living entities.
• Microbes are ubiquitous, found virtually everywhere.
• Living microbes are known as cellular microbes or microorganisms, and include bacteria, archaea, some algae, protozoa, and some fungi.
• Non-living microbes are known as acellular microbes or infectious particles, and include viroids, prions, and viruses.

What Is Microbiology?

• Microbes that cause disease are referred to as "germs" or pathogens.
• Non-pathogens are microbes that do not cause disease, and the majority of microbes are non-pathogens.
• Microbes that live on and in our bodies are referred to as our indigenous microbiota.
• Some members of our indigenous microbiota are opportunistic pathogens, which can cause disease but usually do not.

Categories of Diseases Caused by Pathogens

• Pathogens cause two categories of diseases: infectious diseases and microbial intoxications.

Why Study Microbiology?

• Microbes play significant roles in our lives, and are essential for life on this planet.
• Examples of microbial importance include:
  • Photosynthetic algae and bacteria producing oxygen in the atmosphere.
  • Microorganisms involved in the decomposition of dead organisms and waste products.
  • The use of microbes in bioremediation to clean up toxic wastes.
• Microbes are used in various industries, such as food, beverage, chemical, and antibiotic industries, and in genetic engineering.
• Microbes are used to produce beneficial substances, and are important links in food chains.

First Microorganisms on Earth

• Fossils of primitive microorganisms date back about 3.5 billion years.
• Candidates for the first microorganisms on Earth are archaea and cyanobacteria.
• Infectious diseases of humans and animals have existed for as long as humans and animals have inhabited the planet.

Pioneers in the Science of Microbiology

• Anton van Leeuwenhoek (1632-1723) was the first person to see live bacteria and protozoa, and is known as the Father of Microbiology.
• John Needham supported the theory of abiogenesis, but was later disproven.
• Francesco Redi and Lazaro Spallanzani disproved the theory of spontaneous generation.
• Louis Pasteur developed the pasteurization process, discovered life forms that could exist without oxygen, and developed vaccines.
• Robert Koch developed methods for fixing and staining bacteria, and established Koch's Postulates.

Koch's Postulates

• Koch's Postulates are a scientific procedure to prove that a specific microbe is the cause of a specific infectious disease.
• The postulates require that an organism be isolated from a diseased host, grown in a pure culture, and then be shown to cause the same disease in a healthy host.
• If an organism fulfills Koch's Postulates, it has been proven to be the cause of that infectious disease.

Careers in Microbiology

• Microbiologists study microbes, and can work in various fields, including:
  • Bacteriology
  • Phycology
  • Protozoology
  • Mycology
  • Parasitology
  • Virology
  • Medical microbiology