Introduction to Microbiology

Study Notes

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.

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.

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

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.

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.

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 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.