Introductory Microbiology

MCB 102/MIC 121: Introductory Microbiology

Lecturer: Professor Roseline Ekiomado Uzeh

Meaning and Scope of Microbiology

• Introduction: Microbiology is the study of microorganisms and their activities.
• Definition: Microbiology is the study of microorganisms (bacteria, archaea, fungi, algae, protozoa) and their activities.
• It deals with their form, structure, reproduction, physiology, metabolism, identification, and economic importance.
• The term "microbiology" is derived from three Greek words:
  • mikros (small)
  • bios (life)
  • logos (study)
• Microorganisms are tiny and invisible to the naked eye, requiring a microscope for study.

Where are Microorganisms Found?

Microorganisms were the first living organisms on Earth and are omnipresent:

• In/on humans
• In/on animals
• Plants
• Soil
• Water
• Atmosphere
• Other inanimate objects

Disciplines Related to Microbiology

• Medicine
• Pharmacy
• Agriculture
• Food science
• Molecular biology
• Biochemistry
• Engineering
• Biological Sciences etc.

The Scope of Microbiology (Different Fields)

Microbiology encompasses various specialized fields:

• Food Microbiology: Studies microbial spoilage, foodborne diseases (botulism, salmonellosis), food processing (ogi, nono, wine, cheese, yogurt, beer), and probiotics.
• Medical Microbiology: Focuses on identifying disease-causing microorganisms (disease diagnosis), their control, and treatment in humans.
• Immunology: A branch of medical microbiology studying the immune system and its protection against pathogens.
• Veterinary Microbiology: Deals with microorganisms causing animal diseases, their control, and treatment.
• Industrial Microbiology: Exploits microorganisms for industrial production of antibiotics, vaccines, alcohols, solvents, vitamins, amino acids, and enzymes.
• Agricultural Microbiology: Methods to increase soil fertility and crop yields, biocontrol measures as pesticide substitutes, and prevention of plant diseases.
• Environmental Microbiology: Studies environmental pollution (water, air, soil), bioremediation techniques, and biogeochemical cycles (carbon, nitrogen, phosphorus, sulfur).
• Microbial genetics and Molecular biology: Investigates genetic information of organisms and the detection of new microbial strains for synthesizing useful products.

Historical Development in Microbiology

• Microorganisms were the first living organisms on Earth.
• Early investigators suspected their existence and role in disease even without seeing them.
• Girolamo Fracastoro (1478-1553): Suggested disease was caused by invisible living creatures.
• Francesco Stelluti (1625-1630): Made early microscopic observations on bees and weevils.
• Robert Hook (1665): Published the first drawing of a microorganism in "Micrographia."
• Antony Van Leeuwenhoek: The first person to publish detailed and accurate observations of microorganisms.

Contributions by Antony Van Leeuwenhoek (1632-1723)

• Dutch philosopher, born October 24, 1632.
• Regarded as the "Father of Bacteriology" and "Protozoology."
• Invented a simple microscope with up to x300 magnification.
• Observed bacteria from teeth scrap, naming them "animalcules."
• Discovered bacteria and protozoans (like Paramecium and Amoeba) in rainwater.
• Sent observations with illustrations to the Royal Society.

(Image of Leeuwenhoek's simple microscope showing objective lens, specimen pin, focusing screw, and bracket for observation.)

The Theory of Spontaneous Generation

• The invention of the microscope was crucial, but progress stalled due to insufficient information about microbial biology (colony/colonial morphology).
• Microscopes primarily showed cell or cellular morphology.
• Cell/Cellular Morphology: Describes the shape, structure, form, and size of cells under the microscope.
• Colonial/Colony Morphology: The visual appearance of bacterial or fungal colonies on an agar plate, including their color, shape, elevation, and edge.

Spontaneous Generation (Abiogenesis) vs. Biogenesis

• The discovery of microorganisms by Leeuwenhoek reignited the debate over spontaneous generation.
• Spontaneous Generation (Abiogenesis): The belief that living organisms could develop from nonliving matter.
• Biogenesis: The belief that living things only come from other living things through reproduction.
• Aristotle (384-322 B.C.): Believed simpler invertebrates could spontaneously generate.
• A general belief was that maggots could be produced by exposing meat to warmth and air.

Francesco Redi's Disapproval of Spontaneous Generation (1626-1697)

• Italian physician who disproved spontaneous generation for larger organisms.
• Experiment: Placed meat in three containers:
  1. Open container: Maggots developed (flies laid eggs directly on meat).
  2. Sealed container (cork): No maggots developed.
  3. Gauze-covered container: Maggots developed on the gauze (flies laid eggs on gauze, not meat).
• Conclusion: Maggots came from fly eggs, not spontaneously from meat.

(Image illustrating Redi's experiment: open, cork-sealed, and gauze-covered containers with meat, showing maggots forming only where flies could access or lay eggs.)

John Needham's Experiment in Support of Spontaneous Generation (1713-1781)

• Boiled meat broth for 10 minutes (killing microbes).
• Left the broth open for several days.
• Bacteria grew in the broth.
• Conclusion: Reaffirmed spontaneous generation, claiming "life" in nonliving matter (air and oxygen) caused microbial growth.

Lazzaro Spallanzani's Experiment Against Spontaneous Generation (1729-1799)

• Italian biologist who repeated Needham's experiment in 1768.
• Experiment: Introduced boiled broth into three flasks:
  1. Flask 1: Boiled for 1 hour, mouth sealed by melting.
  2. Flask 2: Boiled for a few minutes, mouth sealed by melting.
  3. Flask 3: Boiled for 1 hour, closed loosely with a cork (allowing air in).
• Result:
  • No growth in Flask 1 (sterilized by prolonged boiling and sealed).
  • Growth in Flask 2 (insufficient boiling to sterilize).
  • Growth in Flask 3 (air allowed microbes to enter).
• Conclusion: Prolonged boiling sterilizes broth; microorganisms enter from the air.

Louis Pasteur's Experiments Against Spontaneous Generation (1822-1895)

Pasteur definitively disproved spontaneous generation for microorganisms.

• Experiment 1 (Cotton Wool Filter):
  • Filtered air through cotton wool and placed it in sterile broth.
  • Microbial growth occurred.
• Experiment 2 (Swan Neck Flasks):
  • Boiled nutrient broth in different flasks: some with straight necks, some with swan necks.
  • Some straight-neck flasks were plugged with cotton wool, others left exposed.
  • The bent long swan neck trapped particulate matter and bacteria from the air.
  • Cotton wool plugs filtered out airborne bacteria.
  • Broth in opened straight-neck flasks spoiled (bad odor, cloudiness, bacteria).
  • Broth in swan neck flasks did not spoil, even with air access (microbes trapped).
  • Broth in cotton-plugged flasks did not spoil.
  • He broke the neck of some swan neck flasks, allowing bacteria to enter, and the broth became contaminated.
• Conclusion: Microorganisms do not arise by spontaneous generation; they come from the air.
• Pasteur resolved the controversy in 1861 and demonstrated how to keep solutions sterile.

(Image depicting Pasteur's swan neck experiment: broth heated and left in a swan neck flask remains sterile, while tilting the flask or breaking the neck allows contact with trapped microbes, leading to growth.)

John Tyndall's Experiments (1820-1893)

• In 1876, Tyndall, an English physicist, supported Pasteur's findings.
• Devised an apparatus demonstrating that air carries particulate matter.
• Found no organisms grew when pure air was introduced into sterile media.
• These results, with Pasteur's, ended the doctrine of spontaneous generation.

The Golden Age of Microbiology

This era was marked by significant advancements and discoveries, largely ushered in by Pasteur's work with swan neck flasks.

Some Achievements During the Golden Age:

• Establishment of the germ theory of disease.
• Improved understanding of microbial metabolism.
• Identification of the role of immunity in preventing and controlling disease.
• Development of vaccines.
• Development of antiseptic techniques.

Contributions by Louis Pasteur (1822-1895)

• French Biochemist, born December 27, 1822.
• Regarded as the "Father of Microbiology and Immunology."
• Proposed the "Germ Theory of Disease" (pathogenic microorganisms cause diseases in plants, animals, and humans).
• Disproved abiogenesis with the "Swan neck flask experiment."
• Discovered aerobic and anaerobic forms of bacteria in the air.
• Discovered the role of anaerobic microbes in sugar fermentation.
• Developed Pasteurization techniques to prevent milk and wine spoilage.
• First isolated Vibrio cholerae, the bacterium causing cholera.
• Developed vaccines against fowl cholera, anthrax, and rabies.
• Developed a technique to strengthen immunity using weakened (attenuated) anthrax bacteria.
• Demonstrated that silkworm disease was caused by the protozoan parasite Nosema bombycis.

Contributions by Robert Koch (1843-1910)

• German microbiologist, born December 11, 1843.
• Made valuable contributions to microbiology and medical science.
• Developed the first culture technique for bacteria in the laboratory.
• Discovered that bacteria caused tuberculosis in humans.
• Developed the first staining technique for bacteria (acidic or basic stain).
• Isolated and identified different kinds of bacteria from various samples.
• Proved Pasteur's Germ Theory of Disease through investigative experiments.
• Awarded the Nobel Prize in Medicine in 1905.
• Formulated Koch's Postulates (principles regarding diseases):
  1. The microorganism or pathogen must be present in all cases of the disease.
  2. The specific pathogen must be isolated from the diseased host and grown in pure culture.
  3. The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible host.
  4. The pathogen must be reisolated from the new host and identified as the same as the original inoculated pathogen.

Contributions by Joseph Lister (1827-1912)

• Developed an antiseptic surgery method to prevent microorganisms from entering wounds.
• Used phenol on surgical dressings.
• Pioneered heat sterilization for surgical equipment.
• His successful approach transformed surgery after his findings were published in 1867.
• Provided strong indirect evidence for the role of microorganisms in disease (Germ Theory of Disease) because phenol killed bacteria and prevented wound infections.
• Together, Louis Pasteur, Robert Koch, and Joseph Lister significantly contributed to the understanding of the Germ Theory of Disease.

Contributions by Alexander Fleming (1881-1973)

• Scottish doctor and biochemist, born in 1881.
• Discovered the antibiotic Penicillin.
• Awarded the Nobel Prize in 1945 for this work.
• His contributions to microbiology include:
  • Studying bacterial action in blood and their response to antibiotics.
  • Working on antimicrobial substances that are toxic to microorganisms but not to humans.
  • Developing techniques to study the sensitivity of microorganisms to antibiotics.