Bio 119/Dalbey History of Microbiology 6/13/2011
READING:
Sec. 1.6
Sec. 1.7
Sec. 1.8
Sec. 1.9
Sec. 1.10
The Historical Roots of Microbiology: Hooke, van Leeuwenhoek, and Cohn
Pasteur and the Defeat of Spontaneous generation
Koch, Infectious disease, and Pure Culture Microbiology
Microbial Diversity and the Rise of General Microbiology
The Modern era of Microbiology
Review Questions #7 - #13 from Chapter 1 p. 10 p. 12 p. 14 p. 18 p. 20 p. 24
History of Microscopes and Microscopy
Robert Hooke, preface to Micrographia, 1665
Lenses of sufficient quality for the construction of useful optical instruments became readily available in the early 17th Century (1600’s) in Western Europe.
The development of telescopes preceeded somewhat that of microscopes, but by the end of the
17 th Century, both astronomy and biology had been revolutionized by these instruments.
The most famous microscopists of the 17 th Century were Robert Hooke and Antony van
Leeuwenhoek.
Robert Hooke (English; ?-1703)
Hooke was a professional scientific journeyman with wide ranging interests in biology, meteorology, surveying and architecture. He was closely connected with the founding of the Royal Society of London and was appointed their first “Curator of
Experiments” in 1662. His magnum opus is the book
(publ. 1665). This is a compendium of scientific observations, mostly by the aid of microscopy, conducted over a number of years at the direction of the Royal Society and profusely illustrated by state of the art illustrations.
Hooke’s engraving of a flea is arguably the most famous scientific illustration of all time.
was widely read and influential at the time of its publication and is prized today by bibliophiles.
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Hooke’s microscope consisted of an objective lens and an ocular, similar to compound microscopes of today. It was probably built by a London instrument maker to his specifications. His major contribution to instrument design was the develoipment of an efficient system of artificial illumination he called a “scotoscope”. Hooke is generally credited with the first published description of cells in his observations on cork. In fact, he was observing only cell walls, and his microscope was generally not capable of resolving cells or microorganisms. Most of the illustrations in his book are of whole insects, seeds, etc.
is currently available on CD; the UCSC Science Library has a copy. There library also has a copy of a Dover facsimile reprint (not currently in print).
Antony van Leeuwenhoek (Lá –wèn-hook) (Dutch; 1632-1723)
Unlike Hooke, Leeuwenhoek was not highly educated and was not a professional scientist. He did not even write Latin, a serious impediment to international scientific communication in nthe 17th
Century. He was a prosperous drapery merchant in Delft who apparently taught himself to grind his own lenses so that he could closely examine the weave of fabrics prior to purchasing them off the ships that had brought them to Dutch ports from Asia.
Leeuwenhoek’s microscopes were a unique design, consisting of only a single tiny lens held between two metal plates. Such was his unequalled expertise in lensmaking, that his simple microscopes were capable of resolving much smaller structures, including microorganisms, than the more complex compound microscopes of Hooke and other contemporary microscopists. His microscopical observations were conducted as a passionate hobby and were communicated to the
Royal Society in a series of letters (in Dutch) over several decades. He is credited with the first published observations of microorganisms, including bacteria.
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Following van Leeuwenhoek, no dramatic advances were made in microscope performance, or in microbiology, for 200 years. In the mid-19th Century several technical developments, both theoretical and practical, revolutionized microscopy and catapulted microorganisms to the forefront of scientific interest. These advances in microscopy were:
• the design of objective lenses highly corrected for chromatic and spherical aberration
• the publication of a theoretical treatment of image formation and resolution by the German optician Ernst Abbe, leading to the invention of the microscope condenser
• the development of artificial staining with coal tar dyes
The most notable subsequent develoments in 19th Century micrbiology were i.) the controversy over the spontaneous generation of microorganisms and ii.) the "germ theory" for the etiology of infectous diseases.
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The Spontaneous Generation Controversy
The spontaneous generation controversy is a clasic example of how scientific consensus emerges from a protracted and bitter controversy. It called forth herculean efforts from some of the greatest names in 19th Century science including Louis Pasteur, John Tyndall, Joseph Lister and
Justus Leibig. It was also important because it motivated the development of many basic laboratory methods microbiologists still use.
Troughout most of Western history, spontaneous generation was widely accepted as fact. The
Presocratic Greek philosophers, particularly the "Atomists", thought that all material bodies consisted of combinations, in varying proportions and arrangements, of a small set of elemental substances (ie. earth, fire, air, water, etc.). The concept of "compositional simplicity" was congenial to the belief that accidental combinations of elemental substances would, by chance, form organic beings.
The notion of spontaneous generation was also congenial to Medieval Christian theology, apparently because it was construed as direct evidence of divine intervention in the contemporary world.
The alchemical literature abounds with recipes for the spontaneous generation of animals: "Throw some old burlap bags in the back corner of the toolshed for six months to produce mice".
During the Renaisannce, spontaneous generation of animals and plants was brought into serious question by a series of "demonstrations", most notably those of Redi. Francesco Redi (1665) showed that maggots did not appear in meat when it was covered by gauze; a demonstration suggested to him by his reading of the Illyiad.
Following the microscopical observation of microorganisms by Van Leeuwenhoek (ca. 1675), the spontaneous generation controversy was reinvigorated by dispute over the spontaneous generation of microorganisms. This question played a key role in motivating many of the early scientific studies on the nature of microbial life forms.
Lazzaro Spallanzani (1765) demonstrated that infusions placed in hermetically sealed flasks and then heated would not putrefy. This demonstration was later applied by Francois Appert to the preservation of food for the French Navy under Napoleon, for which he was awarded a special government prize in 1809.
In the late 18th Century, Priestly, Cavendish and Lavoiser laid the foundation of the chemistry of gasses including O2. That O2 was necessary for animal life was taken by some to invalidate
Spallanzani's experiments. The possibility of anaerobic metabolism was not demonstrated by
Pasteur untill the 19th Century. Pasteur’s famous "Swan-necked" flasks (described in the text) were designed to specifically answer this objection to Spallanzani’s experiments.
The Spontaneous Generation Controversy is a prime example of "Asymmetry of Confirmation and
Negation" in science.
[Pyramid Story; Scott (1957) Adv. Food Res. 7, 83. "Water Relations in Food Spoilage"]
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Joseph Tyndall
A 19th Century English physicist, described the "Tyndall Effect" whose basis is the scattering of light by particles suspended in air. Tyndall's elegant experiments on spontaneous generation are generally less well known than those of his contemporary Pasteur. These experiments incorporated the device known as the “Tyndall Box”, designed to control and anaylyze airborne particulates. Tyndall’s experiments strongly suggested that airborne particulates were or contained microorganisms.
Wait several days until Tyndall Effect subsides.
Fill culture tubes with urine or infusion.
Elevate pan of boilin g brine be low the bo x; heat fluid in culture tubes to >1 00 °C
Fluid i n tubes remains sterile unt il intentionally inoculated.
Clo se Tyndall Box
(Tyndall Effect
Demonstrated)
Fill culturetu bes with urine or infu sion.
Elev ate pan of boiling brine below the box; heat fluid in culture tu bes to >100 ° C
Prolific growth of microorganisms i n fluid.
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Infectous Disease and Clinical Microbiology
Koch's Postulates (see text) are difficult to affirm in many cases of human disease and to some extent they are a matter of historical interest. Even Koch did not specifically formulate and publish the Postulates until well after he had published his studies on Anthrax.
For the pronounciation of "Koch" go to: http://www.forvo.com/word/koch/
Each of the four "postulates" can be considered separately with reference to the status of the
/ Anthrax. HIV / AIDS relation compared to that of
1. Koch was very easily able to demonstrate the presence of
in diseased individuals simply by looking at a small blood specimen with an ordinary light microscope.
HIV and other viruses are not visible with a light microscope. An electron microscope is needed and electron microscopes are more expensive and the methods are more demanding than simply placing a drop of blood on a slide. Additionally, HIV is a retrovirus. This means that many infected cells may not even have complete HIV particles present that could be seen in EM. Instead they may have only a cDNA copy of the HIV genome inserted in a host chromosome. This would not be detected by EM.
Accordingly, standard clinical practice does not involve direct detection of HIV virus per se, but relies instead on detecting the presence of host antibodies against HIV, or by detecting
HIV specific DNA sequences. This is only indirect evidence of HIV infection but it is reasonably reliable.
Another difficulty in satisfying the first postulate for HIV / AIDS stems from the fact that many individuals do not exhibit clinical symptoms of AIDS for many months, or years after infection. Antibodies against HIV are detectable during this "latent" period but meanwhile it may seem that the postulate is invalidated because "healthy" individuals as well as sick individuals are both infected.
2. Luckily for Koch,
is relatively easy to grow in simple artificial laboratory media.
Many bacterial pathogens are more finicky; the agent of leprosy, in contrast, has not yet been grown in pure culture. Viruses, by definition, cannot ever be grown in "pure" cultures because they are not cells. The fallback position is to require that the pathogen, if it cannot be grown in pure culture, be maintained by growth in a pure clonal population of host cells in tissue culture. This is routinely done with HIV. Undoubtedly, if Koch had known of the existence of viruses, this postulate would have been stated in less stringent terms.
3. This requirement cannot be fulfilled on moral grounds unless the pathogen is able to infect a non-human host. Many adherents of the animal rights movement object on moral grounds to using even non-human animals in this type of experiment.
HIV does not reliably cause AIDS in any non-human animal. No human has been intentionally infected with AIDS under controlled laboratory circumstances. However, 3 accidental infections have been reported of individuals who were involved in mishaps while performing lab research on HIV. The outcomes of those incidents are equivocal, but they certainly are quite consistent with the notion that HIV infection causes AIDS.
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4. This requirement does not present any difficulties in addition to #2.
Microorganisms as "Model Organisms" in Basic Research
The development of "molecular biology" as a distinct discipline began in the 1940's and 1950's.
"Biotechnology" emerged in the 1970's. These have been the 2 most historically significant features of biology in the 20th Century and both were predicated on usuing microorganisms as models to study basic biological mechanisms, and as tools.
The attributes of a good model organism include:
Cheap and easy to maintain large experimental populations.
Amenable to genetic manipulation and biochemical anaysis.
Representative of a large area of genetic diversity (i.e. not highly specialized or unusual).
Large body of existing information on the characteristics of the organism.
A short list of classic microbial model microorganisms:
•
(particularly strain K12)
K-12 was isolated in the fall of 1922 from the stool of a convalescent diphtheria patient in Palo Alto, California. In 1925, the culture was deposited in the strain collection of the Department of Bacteriology at Stanford University, where it was used for many years in the teaching laboratories of the department as a typical example of
In the early 1940s, E. L. Tatum, then at Stanford, asked the bacteriology department for some bacteria to test for possible use in his pioneering studies of biochemical genetics. By great good luck he was given
K-12. Strain K-12 is easy to cultivate to high population densities in a chemcally defined growth medium, and has a short generation time. Additionally, strain K12
•
• contained a transmissible plasmid (the "F factor") and is a lysogen carrying the temperate bacteriophage Lambda. These additional genetic elements facilitated genetic manipulation.
• Bacteriophage T4 (and other bacteriophages of the "T" series)
• Bacteriophage Lambda
(a fungus)
(a yeast) - Sometime referred to as "the eukaryotic
".
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Additional Study Questions
1. What practical application was suggested by the experiments on spontaneous generation of microorganisms performed by the Italian naturalist Lazaro Spallanzani in the 18th
Century?
2. On what grounds were Spallanzani's experiments with hermetically sealed flasks criticised by proponents of spontaneous generation?
3. How did the elegant, hand-blown, "swan-necks" in the glass flasks constructed by Pasteur address criticisms of Spallanzani's experiments?
4. What was the major difference in design between the microscope used by Robert Hooke, and the ones constructed by van Leeuwenhoek?
5.
6.
7.
Have Koch's postulates been fulfilled for HIV and AIDS? (See Science 266, 1646.)
Why is agar superior to gelatin as a solidifying agent for bacterial culture media?
Koch denonstrated the bacterial etiology of 2 major human diseases. What were they?
(Note: Anthrax is not a major human disease.)
8. What 19th Century developments in microscopy led to a renaissance in the study of microbiology?
9. What is the "Tyndall Effect" and how is it relevant to microbiology?
10. What model organism/s were used by Alfred Hershey and Martha chase in their famous
"Waring Blendor Experiment" which demonstrated that DNA is the gentic material?
11. Who discovered the first virus, and what virus was it? How was this virus shown to be different than bacteria?
12. What technique of bacterial cultivation allowed Beijerinck and Winogradsky to isolate cultures of nitrogen-fixing bacteria and various chemolithotrophic bacteria?
13. What attributes of E. coli facilitated its success as a model organism?
14. The characterization of "restriction enzymes" was the key that unlocked the door of modern biotechnology. What organism was the first restriction enzyme found in?
15. After restriction enzymes, the next most important enzymes in biotechnology are probably
"DNA ligase" and "Taq DNA polymerase". What organisms are the sources of these enzymes for commercial production? (HINT: Consult an online biotech catalog for a company like New England Biolabs.)
16. The first great commercial success of biotechnology was the production of human insulin by Genentech. What organism is used to produce human insulin commercially?
17. What are the attributes of a good "Model Organism" for Basic research?
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18. Match the names on the left with items on the right.
Robert Hooke Swan-necked flasks
Antony van Leeuwehoek early experiments on spontaneous generation led to the process of canning food
Ferdinand Cohn first isolation of a nitrogen fixing bacterium
John Tyndall
Louis Pasteur first published description of cells in Micrographia single lens microscope
Lazzaro Spallanzani
Sergei Winogradsky
Ernst Abbe
Robert Koch introduced agar as solidifying agent for media first description of a virus devised the technique of enrichment culture devised a strategy for demonstating the bacterial etiology of infectous diseases
Walter and Fanny Hesse directly demonstrated presence of microorganisms suspended in the air
Martinus Beijerinck
Francesco Redi first published descriptions of bacteria developed optical theory on which modern microscope condensers are based described the life cycle of the bacterial genus Bacillus, including endospore formation demonstrated that maggots do not appear in meat protected by gauze from adult female flies
Here is clarification of the roles of Beijerinck (BUY-your-rink) and Winogradsky (win-o-GRADskee) in the isolation of nitrogen-fixing bacteria: Winogradsky isolated the first N-fixing bacterium ( bacterium (
).
), an anaerobe. Beijerinck isolated the first aerobic N-fixing
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References
Milestones in Microbiology
Brock, Thomas D. editor and translator
American Society of Microbiology Press
An annotated collection of original papers from the 16 th to 20
The History of Bacteriology th Centuries.
Bulloch, William (1938)
Oxford Univ. Press
Available in Dover reprint.
Still the most comprehensive and authoritative general source.
Antony van Leeuwenhoek and his "Little Animals"
Dobell, Clifford (1932)
Staples Press Ltd. London
A collection of Leeuwenhoek's letters describing microorganisms in English translation from the
XVIIth Century Dutch originals. Fully annotated, with an introducton and bibliography.
Brian J. Ford's web site has interesting and useful information based on first-hand experience wth van Leeuwenhoek's microscopes and specimens. http://www.sciences.demon.co.uk/wav-mics.htm
The Forgetten Genius
Steven Winwood (2002)
MacAdam/Cage, San Francisco
Comprehensive biography of Robert Hooke.
Molecular Genetics: An Introductory Narrative
Gunther Stent (1971)
W. H. Freeman
This was an early undergraduate textbook in molecular biology, not a hstory of the field.
Phage and the Origins of Molecular Biology
1966
CSHLQB
John Cairns, et al. ed.
A collection of retrospective essays (of variable quality) by some of the pioneers in molecular biology and in which they frequently assert the virtues of their chosen model microorganism.
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