Introduction to Microbes

Definition of Microbiology

• Microbiology encompasses the study of organisms too small to be seen with the naked eye
• Microbes, also known as microorganisms, are commonly referred to as "germs" or "bugs"
• Microbes include bacteria, viruses, fungi, algae, protozoa, helminths, and prions
• Prions, or "infectious proteins", are a recent addition to the list of microbes

Disciplines within Microbiology

• Bacteriology involves studying bacteria
• Mycology studies fungi and yeast
• Virology is the study of viruses
• Parasitology focuses on parasitic protozoans and helminths
• Immunology studies the humoral and cellular immune responses to disease agents and allergens

Importance of Microbiology

• Microbes play key biological roles as decomposers, recyclers, and symbionts
• Microbes aid in animal digestion, especially in ruminants
• Microbes are used in food to make yogurt, cheese, beer, and bread
• Microbes contribute to food safety by preventing putrefaction and disease
• Microbes are used in pharmaceuticals to produce complex drug molecules, such as insulin
• Microbes are also used in bioremediation to clean up pollution
• Pathogenicity is related to bacteria and viruses that make people sick
• Fundamental biology relies on biochemical pathways that scientists have worked out with microbes

History of Microbiology

• Anton Van Leeuwenhoek discovered 'animalcules'
• Robert Hooke discovered cells
• Schwann developed cell theory
• Robert Koch lived from 1843-1910
• Rudolf Virchow determined that cells arise from pre-existing cells
• Carolus Linnaeus developed classification for organisms
• Ferdinand Cohn discovered endospores

More Milestones in Microbiology

• Loius Pasteur contributed vaccines, pasteurization, and germ theory
• Edward Jenner developed vaccines
• Jablot Louis disproved spontaneous generation
• Francesco Redi disproved spontaneous generation
• Allexander Fleming accidentally discovered penicillin in 1929
• Paul Ehrlich worked with vaccines in the 1890s
• Joseph Lord Lister discovered antiseptics and surgical wound infection as well as antiseptic surgery

Advancement of Methods and Culture Media

• Walter Hesse (1846-1911) used agar as a solidifying agent for hardening media and is extracted from seaweeds and red algae
• Rechard Petri (1852-1921) used an agar dish to provide a large area for growth
• Christian Gram (1853-1935) introduced a staining method to demonstrate bacteria and to 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

Discovery of Antibiotics and the Electron Microscope

• Selman Waksman (1940) discovered several antibiotics such as Tetracycline and Streptomycin
• Reska developed the first electron microscope in 1938
• Watson and Crick, Franklin, and Wilkins discovered DNA

Spontaneous Generation

• Aristotle proposed spontaneous generation between 384-322 B.C., stating living things can arise from nonliving matter
• Francesco Redi's experiments showed that decaying meat isolated from flies didn’t develop maggots
• Meat exposed to flies soon became invested
• As a result, scientists began to doubt Aristotle's theory

Louis Pasteur's Contributions

• Louis Pasteur put an end to the Abiogenesis debate with his Goose Neck Flask Experiment
• Louis Pasteur discovered the germ theory but couldn't prove
• Louis Pasteur showed microbes caused fermentation and therefore discovery of Germ Theory
• Louis Pasteur studied spoilage of products like wine and dairy and introduced pasteurization to prevent it
• Louis Pasteur used cotton plugs in his cultures to prevent air borne contamination and devised Aseptic Technique
• Louis Pasteur (1822-1895) discoveries of pasteurization led him to introducing the "germ theory of disease" in 1864
• Louis Pasteur stated that diseases are caused by the growth of microbes in the body, not by sins, bad character, or poverty

Germ Theory

• Robert Koch (1843-1910) used criteria developed by his teacher, Jacob Henle (1809-1895) to establish the relationship between Bacillus anthracis and anthrax
• Koch's criteria became known as Koch’s Postulates and are still used to establish the link between a particular microorganism and a particular disease

Koch's Postulates

• The causative/etiological 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
• During this period, rapid advances, spear-headed by Louis Pasteur and Robert Koch, led to the establishment of microbiology as a science
• Scientists searched for answers to questions like is spontaneous generation of microbial life possible, what causes fermentation and diseases, and how to prevent infection/disease

Emerging Infectious Diseases (EID)

• EIDs involve occurrence of new diseases and increasing incidence of old ones
• Factors include evolutionary changes in existing organisms and the spread of known diseases into new geographical areas by modern transportation
• ecological changes resulting in introduction of unusual agents and the emergence of antimicrobial resistance also contribute to EIDs

Types of EIDs

• West Nile Encephalitis was first diagnosed in Uganda in 1937 and appeared in New York City in 1999
• Invasive Group A Streptococcus, 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 caused by prions
• Acquired Immunodeficiency Syndrome (AIDS) caused by HIV, hits Africa hardest
• Anthrax is caused by Bacillus anthracis and was sensationalized in 2001 when spores were disseminated via the mail
• H5N1 Avian Influenza (Bird Flu) is an EID
• A few flu pandemics include 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 is said to have originated over 3,000 years ago in India or Egypt
• H1N1 Swine Influenza A (Swine Flu) is an EID
• Ebola emerged in 1976

Up and Down

• Diseases that are up and show rising instances: AIDS, Avian Influenza, Ebola, Marburg, Cholera, Rift Valley Fever, Typhoid, Tuberculosis, Leptospirosis, Malaria and Dengue
• Diseases that are down and show decreasing instances: Guinea worm, Smallpox, Yaws, Poliomyelitis, Measles, Leprosy, and Neonatal tetanus