" />


Introduction to Microbiology

Introduction to Microbiology
Microbes and the World
The Science of Microbiology

More to come
More subject specific images will be added to this resource page.

Introduction to Microbiology
•  What are Microbes?
•  The History of Microbiology: Hooke, van Leeuwenhoek, and Cohn
•  Spontaneous Generation and Pasteur
•  Koch and Pure Culture

What are Microbes?
•  While most microbes are unicellular, some multicellular animals and plants are microscopic and broadly defined as microbes.
•  Microbes serve many functions in almost any ecosystem on the Earth, including decomposition and nitrogen fixation.
•  Many microbes are pathogens or parasitic organisms that can harm humans.

The History of Microbiology: Hooke, van Leeuwenhoek, and Cohn
•  Van Leeuwenhoek is largely credited with the discovery of microbes, while Hooke is credited as the first scientist to describe live processes under a microscope.
•  Spallanzani and Pasteur performed several experiments to demonstrate that microbial life does not arise spontaneously.
•  Cohn laid the groundwork for discovering and cataloging microbes, while Koch conclusively showed that microbes can cause diseases.

Spontaneous Generation and Pasteur
•  Before the discovery of microbes, it was widely thought that life, as in the case of rotting food, arose from nothing.This idea was referred to as spontaneous generation.
•  By sterilizing cultures and keeping them isolated from the open air, Pasteur found that contamination of the media only occurred upon exposure to the outside environment, showing that some element was needed to give rise to life.In other words, life does not arise spontaneously.
•  Despite Pasteur’s work and the work of others, it still took a better understanding of germ theory and cell theory to finally displace the concept of spontaneous generation.

Koch and Pure Culture
•  Koch’s research and methods helped link the causal nature of microbes to certain diseases, such as anthrax.
•  As developed by Koch, pure cultures allow the pure isolation of a microbe, which is vital in understanding how an individual microbe may contribute to a disease.
•  According to Koch’s postulates, for an organism to be the cause of a disease, it must be found in all cases of the disease and must be absent from healthy organisms, as well as maintained in pure culture capable of producing the original infection.

Microbes and the World
•  Types of Microorganisms
•  Classification of Microorganisms
•  Microbes and the Origin of Life on Earth
•  Environmental Diversity of Microbes

Types of Microorganisms
•  Microorganisms are divided into six types: bacteria, archaea, protozoa, algae, fungi, and viruses.
•  Each type has a characteristic cellular composition, morphology, mean of locomotion, and reproduction.
•  Microorganisms are beneficial in producing oxygen, decomposing organic material, providing nutrients for plants, and maintaining human health, but some can be pathogenic and cause diseases in plants and humans.

Classification of Microorganisms
•  The classification system is constantly changing with the advancement of technology.
•  The most recent classification system includes five kingdoms that are further split into phylum, class, order, family, genus, and species.
•  Microorganisms are assigned a scientific name using binomial nomenclature.

Microbes and the Origin of Life on Earth
•  The proposed mechanisms for the origin of life on Earth include endosymbiosis and panspermia.Both are debatable theories.
•  In these two theories, bacteria and extremophile archaea are thought to have initiated an oxygenated atmosphere creating new forms of life.
•  Evolutionary processes over billions of years gave rise to the biodiversity of life on Earth.

Environmental Diversity of Microbes
•  Different microbial species thrive under different environmental conditions.
•  Microbial communities occupy aquatic and terrestrial habitats and constitute the majority of biodiversity on Earth.
•  Microbial diversities sustain the ecosystem in which they grow.

The Science of Microbiology
•  Basic Microbiology
•  Applied Microbiology
•  Immunization, Antiseptics, and Antibiotics
•  Modern Microbiology

Basic Microbiology
•  Microbiology focuses on organisms that are very small using various tools, which is a process done by microbiologists.
•  As microbes are essential for human life and as microbes can cause human diseases, microbiology is therefore very important.
•  The numbers of individual microbes and the number of microbes in and on the earth is staggering in proportions.

Applied Microbiology
•  Using knowledge gained by microbiologists studying microbes, several fields of applied microbiology have formed.
•  While food and medicinal applications are a big portion of applied microbiology, the study of microbes has lead to entire commercial industries which affect almost all aspects of human life.
•  There are a myriad of practical applications that microbiology contributes to, including several parts of food production and medicinal applications.

Immunization, Antiseptics, and Antibiotics
•  Immunization is the fortification of our own immune system, priming it against potential future infections by specific microbes.
•  Antiseptics are broadly defined as substances we can use on our body or surfaces around us to slow or kill microbes that could potentially harm us.
•  Antibiotics, like antiseptics, can slow or kill microbes.However, unlike antiseptics, antibiotics can circulate in the human blood system and be used to fight microbial infections.

Modern Microbiology
•  There is some debate as to who was exactly first, but Antonie van Leeuwenhoek, Athanasius Kircher, and Robert Hooke were the first people to view microbes using some of the first self-built microscopes.
•  Ferdinand Cohn, Louis Pasteur, and Robert Koch were pioneers in bacteriology, the discovery and understanding of the subset of microbes that are bacteria.This had a direct and immediate impact on food storage and disease causality.
•  Martinus Beijerinck and Sergei Winogradsky are credited with the discovery of general microbiology, which laid the ground work for our understanding of microbial physiology, diversity, and ecology.


Key terms
•  abiogenesis The origination of living organisms from lifeless matter; such genesis as does not involve the action of living parents; spontaneous generation.
•  anaphylactic shock A severe and rapid systemic allergic reaction to an allergen, constricting the trachea and preventing breathing.
•  animalcule An older term for a minute or microscopic animal or protozoan.
•  anthrax An infectious bacterial disease of herbivores than can also occur in humans through contact with infected animals, tissue from infected animals, or high concentrations of anthrax spores.
•  biodiversity The diversity (number and variety of species) of plant and animal life within a region.
•  biomass The total mass of all living things within a specific area or habitat.
•  biotechnology The use of living organisms (especially microorganisms) in industrial, agricultural, medical, and other technological applications.
•  chemoautotrophy When a simple organism, such as a protozoan, derives its energy from chemical processes rather than photosynthesis.
•  classification the act of forming into a class or classes; a distribution into groups, as classes, orders, families, etc., according to some common relations or attributes.
•  culturable Able to be cultured (grown in a suitable environment).
•  DNA fingerprinting A method of isolating and mapping sequences of a cell’s DNA to identify it.
•  ecosystem The interconnectedness of plants, animals, and microbes with each other and their environment.
•  endosymbiosis A condition of living within the body or cells of another organism.
•  germ theory The germ theory of disease, also called the pathogenic theory of medicine, is a theory that proposes that microorganisms are the cause of many diseases.Although highly controversial when first proposed, germ theory was validated in the late 19th century and is now a fundamental part of modern medicine and clinical microbiology, leading to such important innovations as antibiotics and hygienic practices.
•  Gram stain A method of differentiating bacterial species into two large groups (Gram-positive and Gram-negative).
•  immunogen any substance that elicits a immune response; an antigen
•  immunology The branch of medicine that studies the body’s immune system.
•  metazoa All those multicellular animals, of the subkingdom Metazoa, that have differentiated tissue.
•  panspermia The hypothesis that microorganisms may transmit life from outer space to habitable bodies; or the process of such transmission.
•  pasteurization heat-treatment of a perishable food to destroy heat-sensitive vegetative cells followed by immediate cooling to limit growth of the surviving cells and germination of spores
•  pathogenic Able to cause harmful disease.
•  pathogenic Able to cause harmful disease.
•  peptidoglycan A polymer of glycan and peptides found in bacterial cell walls.
•  quantitation The process of quantitating.
•  rabies a viral disease that causes acute encephalitis in warm-blooded animals and people, characterised by abnormal behaviour such as excitement, aggressiveness, and dementia, followed by paralysis and death
•  rhizosphere The soil region subject to the influence of plant roots and their associated microorganisms.
•  symbiote An organism in a partnership with another such that each profits from their being together.
•  tuberculosis An infectious disease of humans and animals caused by a species of mycobacterium mainly infecting the lungs where it causes tubercles characterized by the expectoration of mucus and sputum, fever, weight loss, and chest pain, and transmitted through inhalation or ingestion of bacteria.

Robert Koch
An image of Robert Koch, a pioneering microbiologist.Koch’s research and methods helped link the causal nature of microbes to certain diseases, including anthrax.

Athanasius Kirche
A portrait of the 17th century Jesuit priest Athanasius Kirche, who arguably discovered microbes.

Louis Pasteur.
The famous scientist Louis Pasteur, one of the founders of microbiology.

Sergei Winogradsky
An image of Sergei Winogradsky,who discovered nitrogen-fixing bacteria.

Antibiotic Testing
Discs soaked with various compounds are put onto a lawn of bacteria.If the compound on the disc kills or slows bacteria growth, a “halo” of clear media is seen.

Antoni Van Leeuwenhoek
A drawing of Antoni Van Leeuwenhoek, one of the first scientists to use a microscope and identify microbes.

Applied microbiology – Fermentation
One of the oldest and well-known examples of applied microbiology is fermentation.In this picture the large tanks are being used for the fermentation of grapes to make wine.

Types of microorganisms
This tree of life shows the different types of microorganisms.

Classification of E. coli
Domain: Bacteria, Kingdom: Eubacteria, Phylum: Proteobacteria, Class: Gammaproteobacteria, Order: Enterobacteriales, Family: Enterobacteriaceae, Genus: Escherichia, Species: E. coli.

Gram Stain
This is a microscopic image of a Gram stain of mixed Gram-positive cocci (Staphylococcus aureus, purple) and Gram-negative bacilli (Escherichia coli, red).

Photosynthetic fossilized cyanobacteria in a billion year old rock formation of Glacier National Park, Montana, USA.

A microbiology officer aboard a US naval ship examines wound cultures in the ship’s microbiology laboratory.

Flu Immunization
A naval officer self-administers a nasal spray that immunizes him against the flu.

A Drawing of Microbes
This is a drawing of what Arthur Hill Hassall saw under a microscope in a sample of water taken from the Thames river at two locations.While not perceptable to the unaided eye, Hassall was actually able to identify many microscopic organisms.

Pasteur’s test of spontaneous generation.
By sterilizing a food source and keeping it isolated from the outside, Pasteur observed no putrefaction of the food source (top panel).Upon exposure to the outside environment, Pasteur observed the putrefaction of the food source (bottom panel).This strongly suggested that the components needed to create life do not spontaneously arise.

Microorganisms in a hot environment
Algae growing in a hot pool in New Zealand.

Microorganisms in a cold environment
Ice algae in Antartica.

•  Wiktionary. “peptidoglycan.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/peptidoglycan
•  Wikipedia. “Microorganisms.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microorganisms
•  Wikipedia. “Gram stain.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Gram%20stain
•  Wikipedia. “Koch’s postulates.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Koch%2527s_postulates#Koch.E2.80.99s_postulates_for_the_21st_century
•  Wikipedia. “Koch’s postulates.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Koch%2527s_postulates#Koch.E2.80.99s_postulates_for_the_21st_century
•  Wiktionary. “anthrax.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/anthrax
•  Wiktionary. “tuberculosis.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/tuberculosis
•  Wiktionary. “metazoa.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/metazoa
•  Wikipedia. “Robert Koch.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Robert_Koch
•  Wikipedia. “Microbiological culture.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microbiological_culture#Isolation_of_pure_cultures
•  Wikipedia. “Anthrax.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Anthrax
•  Wikipedia. “Taxonomy.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Taxonomy
•  Wikipedia. “Binomial nomenclature.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Binomial_nomenclature
•  Wikipedia. “DNA fingerprinting.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/DNA%20fingerprinting
•  Wikipedia. “Microbiology.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microbiology#Applied_microbiology
•  Wiktionary. “rhizosphere.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/rhizosphere
•  Wiktionary. “biotechnology.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/biotechnology

•  Wiktionary. “pathogenic.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/pathogenic
•  Wikipedia. “Microecology.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microecology
•  Wiktionary. “biodiversity.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/biodiversity
•  Wiktionary. “biomass.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/biomass
•  Connexions. “Connexions.” CC BY 3.0 http://cnx.org/contents/[email protected]
•  Wikipedia. “Microorganism.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microorganism
•  Wikipedia. “Microorganism.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microorganism
•  Wikipedia. “Microbe.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microbe
•  Wikipedia. “Microorganism.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microorganism
•  Wiktionary. “ecosystem.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/ecosystem
•  Wiktionary. “pathogenic.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/pathogenic
•  Wiktionary. “symbiote.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/symbiote
•  Wikipedia. “Spontaneous generation.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Spontaneous_generation
•  Wikipedia. “Spontaneous generation.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Spontaneous_generation
•  Wikipedia. “Louis Pasteur.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Louis_Pasteur
•  Wiktionary. “abiogenesis.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/abiogenesis
•  Wikipedia. “germ theory.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/germ%20theory
•  Wikipedia. “Microbiology.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microbiology#Modern
•  Wiktionary. “rabies.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/rabies

•  Wiktionary. “pasteurization.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/pasteurization
•  Wiktionary. “chemoautotrophy.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/chemoautotrophy
•  Wiktionary. “animalcule.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/animalcule
•  Wiktionary. “quantitation.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/quantitation
•  Wiktionary. “immunology.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/immunology
•  Wiktionary. “culturable.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/culturable
•  Wikipedia. “Microbiology.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microbiology
•  Wikipedia. “Archaea.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Archaea
•  Wikipedia. “Endosymbiont.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Endosymbiont#Endosymbiosis_theory_and_mitochondria_and_chloroplasts
•  Wikipedia. “Panspermia.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Panspermia
•  Wiktionary. “panspermia.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/panspermia
•  Wiktionary. “endosymbiosis.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/endosymbiosis
•  Wikipedia. “Microbes.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microbes#Classification_and_structure
•  Wiktionary. “classification.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/classification
•  Wikipedia. “Microbes.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Microbes#Classification_and_structure
•  Wikipedia. “Ferdinand Cohn.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Ferdinand_Cohn
•  Wikipedia. “Ferdinand Cohn.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Ferdinand_Cohn
•  Wikipedia. “Antiseptics.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Antiseptics
•  Wikipedia. “Immunization.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Immunization

•  Wikipedia. “Immunization.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Immunization
•  Wikipedia. “Antibiotics.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Antibiotics
•  Wikipedia. “Antiseptics.” CC BY-SA 3.0 http://en.wikipedia.org/wiki/Antiseptics
•  Wiktionary. “anaphylactic shock.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/anaphylactic+shock
•  Wiktionary. “immunogen.” CC BY-SA 3.0 http://en.wiktionary.org/wiki/immunogen

Skip to toolbar