Introduction to Microbiology

• Microbiology is the study of organisms too small to be seen with the naked eye.
• Microbes or microorganisms, commonly called "germs" or "bugs", include bacteria, viruses, fungi, algae, protozoa, and helminths.
• Prions ("infectious proteins") have been recently added to the list of microbes.

Disciplines of Microbiology

• Bacteriology: The study of bacteria.
• Mycology: The study of fungi and yeast.
• Virology: The study of viruses.
• Parasitology: The study of parasitic protozoans and helminths.
• Immunology: The study of the humoral and cellular immune response to disease agents and allergens.

Importance of Microbiology

• Biological roles include functioning as decomposers, recyclers, and symbionts.
• Microbes aid in animal digestion, especially in ruminants.
• Food microbiology involves the production of yogurt, cheese, beer, bread, etc.
• Microbes contribute to food safety by preventing putrefaction and disease.
• Microbes are used in the production of complex drug molecules like insulin.
• Bioremediation uses microbes to clean up pollution.
• Pathogenicity refers to bacteria and viruses that cause illness.
• Fundamental biology utilizes microbes to understand most biochemical pathways.

History of Microbiology

• Anton Van Leeuwenhoek discovered 'animalcules'.
• Robert Hooke discovered cells.
• Schwann developed cell theory.
• Robert Koch lived from 1843-1910.
• Rudolf Virchow stated that cells arise from pre-existing cells.
• Carolus Linnaeus is known for classification.
• Ferdinand Cohn discovered endospores.
• Louis Pasteur contributed to vaccines, pasteurization, and Germ Theory.
• Edward Jenner developed vaccines.
• Jablot Louis disproved spontaneous generation.
• Francesco Redi disproved spontaneous generation.
• Alexander Fleming (1929) accidentally discovered penicillin.
• Paul Ehrlich (1890s) contributed to vaccines.
• Joseph Lord Lister developed antiseptics for surgical wound infection, known as the Father of Antiseptic Surgery.
• Walter Hesse (1846-1911) used Agar as a solidifying agent for media.
• Richard Petri (1852-1921) used the agar dish for providing a large area for growth.
• Christian Gram (1853-1935) introduced a staining method to demonstrate bacteria and distinguish between Gram-positive and Gram-negative bacteria.
• Raymond Sabouraud (1890-1910) developed culture media to study yeast and molds.
• Dimitri Ivanovski (1892) found that the tobacco mosaic virus could pass through filters used to remove bacteria.
• Selman Waksman (1940) discovered a number of antibiotics such as Tetracycline and Streptomycin.
• Reska (1938) developed the first electron microscope.
• Watson and Crick, Franklin, and Wilkins discovered DNA.

Spontaneous Generation

• Aristotle (384-322 B.C.) proposed spontaneous generation, stating that living things can arise from nonliving matter.
• Francesco Redi's experiments:
  • Decaying meat kept isolated from flies did not develop maggots.
  • Meat exposed to flies soon became infested.
  • Scientists began to doubt Aristotle's theory.

Louis Pasteur

• Louis Pasteur ended the Abiogenesis debate with his Goose Neck Flask Experiment.
• He discovered the germ theory but couldn't prove it.
• He is considered the father of microbiology.
• Microbes caused fermentation, leading to the discovery of the Germ Theory.
• Studied spoilage of wine, dairy products, etc., and introduced “Pasteurization" to prevent it.
• Used cotton plugs in his cultures to prevent air borne contamination and devised the Aseptic Technique.
• His discovery of pasteurization led him to introduce the "germ theory of disease" in 1864.
• Diseases are caused by the growth of microbes in the body and not by sins, bad character, or poverty.

Germ Theory of Diseases and Koch's Postulates

• Robert Koch (1843 - 1910) established the relationship between Bacillus anthracis and anthrax using criteria developed by Jacob Henle (1809-1895).
• His criteria became known as Koch's Postulates, used to establish the link between a particular microorganism and a disease.
• Koch's Postulates:
  • The causative agent must be present in all affected organisms but absent in healthy individuals.
  • The agent must be capable of being isolated and cultured in pure form.
  • When the cultured agent is introduced to a healthy susceptible organism, the same disease must occur.
  • The same causative agent must be isolated again from the affected host.

Golden Age of Microbiology

• The period from 1860 to 1900 is often named the Golden Age of Microbiology.
• Rapid advances, spearheaded by Louis Pasteur and Robert Koch, led to the establishment of microbiology as a science.
• Scientists searched for answers to questions such as:
  • Is spontaneous generation of microbial life possible? (Aristotle, Jablot, Redis, Louis Pasteur)
  • What causes fermentation? (Louis Pasteur)
  • What causes disease? (Louis Pasteur, Robert Koch)
  • How can we prevent infection and disease?

Emerging Infectious Diseases (EID)

• Occurrence of new diseases and increasing incidence of old ones (EID)
• Factors include:
  • (a) evolutionary changes in existing organisms
  • (b) spread of known diseases into new geographical areas by modern transportation
  • (c) ecological changes resulting in the introduction of unusual agents
  • (d) emergence of antimicrobial resistance

Examples of EIDs

• West Nile Encephalitis was first diagnosed in Uganda in 1937 and appeared in New York City in 1999.
• Invasive Group A Streptococcus is also known as the "flesh-eating bacteria."
• Escherichia coli 0157:H7 causes "bloody diarrhea" and hemorrhagic uremic syndrome (HUS).
• Bovine Spongiform Encephalopathy (BSE) or "mad cow" disease is caused by prions.
• Acquired Immunodeficiency Syndrome (AIDS) is caused by HIV, with Africa being the hardest hit.
• Anthrax, caused by Bacillus anthracis, was sensationalized in 2001 when spores were disseminated via the mail.
• H5N1 Avian Influenza (Bird Flu).
• Three flu pandemics have occurred in the past century, including the Spanish flu of 1918, Asian flu of 1957, and the 1968 Hong Kong flu.
• Smallpox is a contagious disease caused by a virus that originated over 3,000 years ago in India or Egypt

Other EIDS

• H1N1 Swine Influenza A (Swine Flu).
• Ebola (1976).

Trends in Diseases

• Diseases that are increasing include:
  • AIDS, Avian Influenza, Ebola, Marburg, Cholera, Rift Valley Fever, Typhoid, Tuberculosis, Leptospirosis, Malaria and Dengue
• Diseases that are decreasing include:
  • Guinea worm, Smallpox, Yaws, Poliomyelitis, Measles, Leprosy and Neonatal tetanus.