Chapter
1: The Microbial World and You
The introduction to microbiology readily divides students into two groups, those who handle abstract information well and those that do not. Unlike Anatomy and Physiology, the majority of material covered in Microbiology is focused on invisible objects with no common frame of reference. Compound this abstraction with a new vocabulary that rivals many "foreign language" classes and you can easily get into information overload. The trick to Microbiology is to look for the core concepts in the chapters, what "big pictures" were developed and then add the details. Let us take the opportunity to look at these concepts for this chapter.
Microorganisms exist through out every inhabitable niche of our environment, and can be considered the most successful form of life on the planet.
Microorganisms (and all other life) have a specific naming convention that facilitates information transfer
There are six (6) major types of microorganisms that have differing characteristics
Grouping of microorganisms is accomplished the Three Domain system
The modern science of microbiology is built upon the accomplishments of many before.
OUTLINE
I. Microbes
in our Lives
A. Microbes (Microorganisms) are life forms that are almost always too small to be seen individually with an unaided eye.
B. Microbes represent the most diverse form of life on the planet, occupying environmental niches as diverse as high temperature vents deep in the oceans and near frozen buried lakes in Antarctica.
C. While many microbes are pathogenic, there are many more that are not harmful, and possibly even useful to mankind.
D. Microbes and microbiology have application through out the world around you. Everything from beer and wine to the destruction of dangerous chemicals are accomplished through microbes.
II.
Naming and Classifying Microorganisms
A. Nomenclature
1. Nomenclature is the process by which organisms are given a scientific name.
2. Latin is used for historical reasons and because it is a dead language (not utilized by any extant culture), therefore grammar and syntax will not change over time.
3. The current system of nomenclature was developed by Charles Linnaeus in 1735.
4. All organisms have a scientific name that is composed of a genus (plural: genera) name that denotes a broader family relationship and a species name that denotes the specific type of organism.
5. The genus is always capitalized and the species lower-case by convention.
6. Many scientific names are descriptive, such as honoring a researcher or the location an organism was discovered.
B. Types of Microorganisms
1. Bacteria
a. Unicellular organisms.
b. The genetic material is not bound in a nucleus so these are considered prokaryotes.
c. The outer structural shell of bacteria is composed of a compound call peptidoglycan.
d. Asexual
2. Archaea
a. Unicellular organisms
b. Prokaryotes
c. Outer structural shell does not contain peptidoglycan
d. Often found in extreme environments (i.e. methanogens and thermophiles)
e. Asexual
3. Fungi
a. Unicellular and multicellular organisms
b. The genetic material is bound in a nucleus so these are called eukaryotes
c. Outer structural shell is composed of a chemical called chitin
d. Can be either microscopic
or macroscopic
e. The most common varieties
are grouped as molds, mushrooms,
and slime molds
f. Can reproduce sexually or asexually
4.
Protozoa
a. Unicellular organisms
b. Eukaryotes
c. Motile by means of a pseudopod, flagella, or cilia
d. Can be free-living or parasitic
e. Can reproduce sexually or asexually
5. Algae
a. Unicellular and Multicellular organisms
b. Photosynthetic
c. Can reproduce sexually or asexually
6. Viruses
a. Acellular
b. Majority are smaller than other microorganisms
c. No independent metabolism or reproduction
d. Parasitic
C. Classification of Microorganisms
1. Since Linnaeus scientists have debated how to best divide the types of life on this planet.
2. Two major schemes are utilized now
a. Five Kingdoms
i. Based on the traditional observation methodology
ii. Classical methodology, mainly used by biologists who deal with macroscopic organisms
iii. Contains the Kingdoms: Plant, Animal, Fungus, Protist, and Monera
iv. Not commonly used in modern microbiology
b. Three Domains
i. Proposed in 1978 by Carl Woese
ii. Based on molecular genetics, considered the gold standard at the time.
iii. Much better at demonstrating the inherent diversity in the microscopic world, but deemphasizes the macroscopic kingdoms
iv. Led to the discovery that there were three inherently different forms of life on Earth: Bacteria, Archaea, and Eukarya
v. Eukarya is composed of the Plant, Animal, Protist and Fungus kingdoms, while Monera was divided into the Bacteria and Archaea
vi. Not commonly used outside of microbiology
vii. The system we will use in this class
III. A Brief History of Microbiology
A. The First Observations
1. 1665- Robert Hooke observes the microscopic structure or thin slices of cork, marking the beginning of cell theory (that all living things are composed of cells)
2. 1673-1723- Anton van Leeuwenhoek, a Dutch merchant and amateur scientist, discovers “animalcules” in a variety of sources (feces, pond water, etc.) that he documents and publishes in letters to the Royal Society of London.
B. The Debate over Spontaneous Generation
1. Spontaneous Generation (SG)
a. Spontaneous Generation was theory held by many scientists and philosophers in until the second half of the nineteenth century.
b The theory was an attempt to explain how life could arise
c. The theory stated that it was possible for new life to arise spontaneously from nonliving matter.
d. The most common example is that maggots were thought to arise from decaying flesh.
2. Experimental Evidence
a. Redi and the flies
i. 1668- Francesco Redi provided evidence against SG by showing that if flies were not allowed to settle on decaying meat maggots did not arise.
ii. Opponents criticized his work for originally not allowing air into the meat; Redi corrected the problem by blocking the flies with fine mesh.
b. Needham and Chicken Broth
i. 1745- John Needham boiled broth before pouring it into sealed bottles. Microorganisms appeared in the sealed bottles after a few days.
ii. Needham claimed that the boiling killed any preexisting microorganisms and therefore new ones arose from the boiled fluids, supporting SG.
c. Spallanzani and the Return of Chicken Broth
i. 1765- Lazzaro Spallanzani repeated Needham’s work, but boiled the broth after it was sealed in bottles. No microorganisms arose in Spallanzani’s bottles.
ii. Spallanzani argued that microorganisms had arisen in Needham’s bottles due to contamination after the broth was boiled, but before it was sealed.
iii. Critics cited that oxygen was not allowed into Spallanzani’s sealed bottles and therefore it was impossible for life to arise, citing contemporary work by Lavoisier that an atmospheric gas, oxygen, was needed for life to arise.
3. The Theory of Biogenesis
a. 1858- Rudolf Virchow proposed the theory that living cells could only arise from preexisting living cells.
b. 1861- Louis Pasteur finally disproved the SG theory through a detailed repetition of Needham’s and Spallanzani’s work.
c. Louis Pasteur continued to demonstrate that all materials he tested had some microorganisms present on or in them and these could be killed with heat.
d. Pasteur’s work formed the basis of aseptic technique
C. The Golden Age of Microbiology (1857-1914)
1. Fermentation and Pasteurization
a. Louis Pasteur was asked to determine why beer and wine spoiled.
b. Pasteur found that beer and wine were made by microorganisms called yeast driving a process called fermentation.
c. When bacteria contaminate the process they cause different chemicals to be formed and this causes spoilage.
d. Pasteur’s solution was to use heat to kill the contaminating bacteria, a process now called pasteurization.
2. The Germ Theory of Disease
a. Scientists began to believe that if yeast could affect change in the chemistry of wine, that microorganisms might also be responsible for disease.
b. This was a difficult leap for the general population of western civilization, because most still believed that disease was a punishment for some transgression and now scientist were putting forth the notion that disease could be an objective action by an invisible object.
c. 1865- Pasteur and the Silkworm
i. The silk industry in Europe was being destroyed by a mysterious disease afflicting the silkworms.
ii. Pasteur (utilizing data and techniques from an amateur microscopist, Bassi) determined that infected silkworms carried a certain protozoan.
iii. Pasteur developed a way to detect afflicted silkworm moths and cull them from the group.
d. 1860s- Lister and the Hospital
i. Ignaz Semmelweis demonstrated that surgeons who did not was there hands routinely transmitted infections between patients.
ii. Carbolic acid (Phenol) was known to kill microorganisms.
iii. Joseph Lister showed that if surgeons would treat wounds with Phenol that they would reduce infections, thereby saving patients and preventing the further transmission through hospitals
e. 1876- Koch and Anthrax
i. Anthrax was responsible for the death of as much as ¼ of the livestock in Europe per year during the late 1800s.
ii. Pasteur and Robert Koch were in a race to determine the cause of anthrax
iii. Koch was the first to isolate a bacterium from a known disease (Bacillus anthracis)
iv. He further demonstrated that his isolated bacterium was the responsible agent by using the isolate to experimentally infect healthy animals and then reisolated the same bacterium from the new animals. (Koch’s Postulates)
3.
Vaccination
a. The first vaccine to be used intentionally in western civilization was the smallpox vaccination.
b. 1796- Edward Jenner developed a way to prevent smallpox in humans by purposely infecting them with a milder disease (cowpox).
c. Jenner didn’t know how his procedure worked in a strict sense, but he was being pragmatic, in that smallpox was a plague that routinely killed 30% of the Europeans infected.
d. The vaccine was said to promote immunity to the disease.
e. Pasteur had the first notable success at creating an artificial vaccine (he coined this term in deference to Jenner’s work).
D. The Birth of Modern Chemotherapy: Dreams of a “Magic Bullet”
1. Now that microorganisms were known to cause a multitude of the diseases that afflicted humans, scientists turned to ways to kill these organisms after they had infected people.
2. Synthetic Drugs
a. 1910- Paul Erlich discovers the activity of salvarsan, an arsenic derivative, against syphilis.
b. In the 1930s, organic chemists were constantly testing chemicals for antimicrobial action. Most of these were derived from dyes and had a large number of side effects.
3. Antibiotics
a. Alexander Fleming found (by accident) that a certain mold could inhibit the growth of certain bacteria. In 1928 he named this soluble factor penicillin.
b. This discovery led to the mining of natural microorganisms for further antibiotics.
c. In some ways antibiotics are the victims of their own success. Their overuse and indiscriminant use has allowed for the development of bacteria resistant to antibiotics.
E. Modern Developments in Microbiology
1. Modern microbiology is so complex that it is typically divided into many subdisciplines.
a. Bacteriology: The study of bacteria
b. Mycology: The study of fungi
c. Parasitology: The study of protozoa and parasitic worms
d. Virology: The study of viruses
e. Immunology: The study of the immune system and its interactions with disease organisms.
2. The greatest advances in modern microbiology have come through the use of recombinant genetic techniques, where scientist can manipulate the very code that governs an organism’s life. This technology has allowed for the creation of novel vaccines, consumer products, and drugs.
IV. Microbes and Human Welfare-Benefits
A. Recycling Vital Elements
B. Sewage Treatment
C. Bioremediation
D. Insect Control
E. Recombinant Technology
V. Microbes and Human Disease-Harmful
A. Normal Microbiota
B. Infectious Disease
C. Emerging Infectious Diseases