Chapter 2 - History of Microbiology

Question 1

Upon which two basic methods is microbiology founded?

Answer 1

1. Microscopy
2. Pure culture technique

Question 2

Why is microscopy important to the field of microbiology?

Answer 2

Microbes are very small and require microscopes to be seen

Question 3

Why is pure culture technique important to the field of microscopy?

Answer 3

Because each individual type of microbe must be separated from others in order for study

Question 4

What do we mean by resolution?

Answer 4

The ability of a microscope to differentiate between two objects

Question 5

Who discovered microbes

Answer 5

Leeuwenhoek

Question 6

How did Leeuwenhoek discover microbes? In other words, what type of microscope did he use?

Answer 6

A simple microscope with a lens of unusually high quality

Question 7

Why did simple microscopes offer better quality images than compound microscopes in the 18th century?

Answer 7

Although compound microscopes offer many advantages, they must be made of exceptionally high-quality lens because any distoritions in the first lens are magnified by the second. Simple microscopes therefore offered higher quality images because of their lesser distortion

Question 8

In what century did Leeuwenhoek discover microbes?

Answer 8

The 16th century

Question 9

What was the principal innovation that lead to the improvement of the compound microscope?

Answer 9

The replacement of each of the lenses in the compound microscope with a set of lenses that were designed to correct a particular type of distortion

Question 10

The final step in the evolution of the compound microscope was the development of the ________________, a device that proces an even illumination of the specimen.

Answer 10

Condenser

Question 11

Advances in ________________ during the 19th century led to improved ____________________________.

Answer 11

Optics

Microscopes

Question 12

Advances in ___________ ____________________ in the 20th century were largely confined to improved methods of enhancing ___________________.

Answer 12

Light microscopy

Contrast

Question 13

What approach did scientists use to enhance contrast in the 19th and early 20th century?

Answer 13

Staining

Question 14

What was the primary disadvantage of using staining to contrast microbial specimens?

Answer 14

Normally the stains used killed the cells

Question 15

What two innovations in the 20th century led to greater improvements in contrast?

Answer 15

1. Phase-contrast microscopy
2. Darkfield microscopy

Question 16

_________________ microscopy makes objects much darker than they would otherwise be, whereas _________________ microscopy shows them as bright objects against a black background.

Answer 16

Phase-constrast microscopy

Darkfield microscopy

Question 17

What was the most significant advance in microscopy in the 20th century?

Answer 17

The electron microscope

Question 18

The limit of resolution for an electron microscope is at least a ______________________ times better than the light microscope.

Answer 18

1000 times

Question 19

Light microscopes cannot visualize objects less than ____ _______. Electron microscopes can theoretically visualize the smallest of objects, but practical issues limit visualization to a _______________ or less.

Answer 19

0.1 µm

1 nm

Question 20

What did Leeuwenhoek call the microbes moving around in pond water?

Answer 20

Animalcules

Question 21

For most of human history, people believed that life came from the three processes. What were they?

Answer 21

1. Sexual reproduction
2. Asexual reproduction
3. Spontaneous generation

Question 22

What is the idea of spontaneous generation?

Answer 22

The supposed production of living organisms from nonliving matter, as inferred from the apparent appearance of life in some supposedly sterile environments.

Question 23

Who is credited with presenting the concept of spontaneous generation?

Answer 23

Aristotle

Question 24

Aristotle proposed that life arose from nonliving material if the material contained _______ ______.

Answer 24

Vital heat

Question 25

_______________ _____________ planted the first seed of doubt regarding spontaneous generation with his “meat and maggot” experiment.

Answer 25

Francisco Redi

Question 26

How did Redi demonstrate that spontaneous generation was unlikely?

Answer 26

He placed three slices of meat in three containers. The first container was left unopened. The second was corked and sealed. The third was covered with gauze. Maggots developed on top of the meat in the first container. Maggots did not develop on the meat in the second and only developed on top of the gauze in the third. Prior to this, it was believed that meat “spontaneously generated” maggots; Redi’s experiment showed that maggots were the eggs of flies

Question 27

______________ _________________ “life gravy” experiments challenged Francisco Redi’s “meat and maggots” experiment and supported the idea of spontaneous generation.

Answer 27

John Needham

Question 28

How did John Needham “prove” the theory of spontaneous generation?

Answer 28

Needham placed a broth, or “gravy,” into a bottle, heated the bottle to kill anything inside, then sealed it. Days later, he reported the presence of life in the broth and announced that life had been created from nonlife

Question 29

___________________ is the Greek word Aristole used to characterize the “life gravy” or “life force” that causes inanimate objects to come to life.

Answer 29

Pneuma

Question 30

Who repeated John Needham’s “life gravy” experiment?

Answer 30

Lazzaro Spallanzani

Question 31

How did Spallanzani identify errors in Needham’s “life gravy” experiments?

Answer 31

He reviewed both Redi’s and Needham’s data and concluded that perhaps Needham’s heating of the bottle did not kill everything inside. He constructed his own experiment by placing broth in two separate bottles, boiling the broth in both bottles, then sealing one bottle by melting its opening and leaving the other open. Days later, the unsealed bottle was teeming with small living things that he could observe more clearly with the newly invented microscope. The sealed bottle showed no signs of life. This certainly excluded spontaneous generation as a viable theory

Question 32

What three conclusions did Spallanzani make after conducting his experiment?

Answer 32

1. Needham did not heat the broth long enough or did not properly seal the bottles
2. Microorganisms exist in the air and can contaminate the broth
3. Spontaneous generation does not exist, and living things only arise from other living things

Question 33

Why did critics of the time reject Spallanzani’s conclusions?

Answer 33

Because they believed air was required for spontaneous generation and/or that the heating killed the “life force” required for spontaneous generation to occur

Question 34

The controversy over spontaneous generation required the development of ____________________ methods.

Answer 34

Sterilization

Question 35

_________________________’s “swan-necked flask” experiments convinced the scientific community that spontaneous generation was incorrect.

Answer 35

Louis Pasteur

Question 36

_______________________ discovered that spores were heat resistant and discovered a reliable way to kill them through repeated boiling.

Answer 36

John Tyndall

Question 37

How did Pasteur provide evidence against spontaneous generation?

Answer 37

Pasteur made a series of flasks with long, twisted necksin which he boiled broth to sterilize it. His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists of the flasks’ necks. If a life force were responsible for microbial growth, it would have access to the broth, whereas the microorganisms would not. After several weeks, Pasteur observed that the broth in the straight-neck flask was discolored and cloudy, while the broth in the curved-neck flask had not changed

Question 38

What theory of disease provided an explanation for the phenomenom of contagion?

Answer 38

The germ theory of disease

Question 39

What is contagion?

Answer 39

The ability of a disease to pass from one person to another

Question 40

What disease led to the formulation of the germ theory of disease?

Answer 40

Anthrax

Question 41

Fermented drinks have been around for a long time. How far back do we have evidence of fermented drinks?

Answer 41

7000 BCE in northern China

Question 42

Jars of wine estimated to be from ________ BCE werer found in Iran (Babylon); from 3000 BCE in Egypt; from _______ BCE from “Mexico”; and from 1500 BCE from _________.

Answer 42

5000 BCE - Iran

3000 BCE - Egypt

2000 BCE - Mexico

1500 BCE - Sudan

Question 43

Who determined that yeast is responsible for fermentation?

Answer 43

Louis Pasteur

Question 44

Be familiar with how Pasteur determined yeast to be the cause of fermentation.

Answer 44

Question 45

How did Pasteur demonstrate that bacteria did not lead to fermentation?

Answer 45

When Pasteur sealed a flask of juice with bacteria, no alcohol was produced, only acid

Question 46

How did Pasteur determine that yeast fermented grape juice into wine?

Answer 46

In an experiment, he removed all yeast from grape juice but found that it did not ferment; when he added the yeast back, the grape juice fermented into wine. He suggested that grape juice be heated to destroy all life before fermentation was begun, what we call pasteurization

Question 47

Why should you not drink wine that has been left open for a week?

Answer 47

Because it becomes vinegar as bacteria colonize the wine and release acids

Question 48

As early as _______ CE, the idea that microbes caused disease was floating around.

Answer 48

1000 CE

Question 49

Who finally demonstrated that bacteria caused the disease anthrax and not something else?

Answer 49

Robert Koch

Question 50

What is the scientific name of the bacteria that causes anthrax?

Answer 50

Bacillus anthracis

Question 51

Prior to Koch, several people had shown that _________ from a cow with anthrax would cause other cows injected with its blood to die.

Answer 51

Blood

Question 52

Who was the first to publish photographs of bacteria?

Answer 52

Robert Koch

Question 53

How did Koch demonstrate that bacteria caused anthrax?

Answer 53

He injected a drop of sheep blood - from a sheep that died from anthrax - into a mouse, and the mouse died within the next day. When he studied blood from the spleen of the mouse, he found the same bacteria present from the sheep blood. Koch ultimately did this 20 times, demonstrating that the bacteria was alive and reproduced while maintaining its pathogenic nature throughout

Question 54

___________ _______________ techniques were required to show that different diseases were caused by different microbes.

Answer 54

Pure culture technique

Question 55

Koch’s work with cultures and potato slices, led him to realize that pure cultures required what type of medium in which to grow?

Answer 55

Solid surfaces, not liquid media

Question 56

A colony is a series of ___________ growths while; each colony - if homogenous - represents a ____ ________.

Answer 56

Localized growths

Pure culture

Question 57

Why was gelatin a poor substrate for pure culture techniques?

Answer 57

Gelatin melts at the temperature at which most cultures of disease-causing bacteria grow, and gelatin is often broken down as a nutrient by bacteria

Question 58

What did Koch find to be the best material for pure culture techniques?

Answer 58

Agar

Question 59

What are three reasons as to why agar is such a useful medium for pure cultures?

Answer 59

1. After being melted, agar can remain a liquid until temperatures of less than 50 degrees Celsius (easily pourable)
2. After solidifying, it remained so up to 100 degrees celsius
3. A derivative of marine algae, it is not normally attacked by bacteria

Question 60

The Petri dish is named after who?

Answer 60

Julius Petri, an assistant of Koch

Question 61

What is the streak plate technique used for?

Answer 61

Streak plate technique is used for the isolation into pure culture of the organisms (mostly bacteria), from mixed population. The inoculum is streaked over the agar surface in such a way that it “thins out” the bacteria. Some individual bacterial cells are separated and well spaced from each other. As the original sample is diluted by streaking it over successive quadrants, the number of organisms decreases. Usually by the third or fourth quadrant only a few organisms are transferred which will give discrete colony forming units (CFUs).

Question 62

Koch’s postulates define what is logically necessary and sufficient to prove the microbial etiology of a disease. What are the four postulates?

Answer 62

1. The microbe must be present wherever the disease is present, but absent from healthy organisms
2. The microbe must be isolated from the diseased host organism and obtained in pure culture
3. The microbe must be inoculated back into a healthy susceptible host, which must becomme ill with the same disease
4. The same microbe must be found in the experimentally infected host

Question 63

1. The microbe must be __________ wherever the disease is present, but ____________ from healthy organisms
2. The microbe must be ____________ from the diseased host organism and obtained in _____ ____________
3. The microbe must be ______________ back into a healthy _____________ host, which must becomme ill with the same disease
4. The same microbe must be found in the experimentally infected host

Answer 63

Present, absent

Isolated, pure culture

Inoculated, susceptible

Question 64

What acronym can be used for the four postulates of Koch’s germ theory?

Answer 64

PIOII

Question 65

What allows for the isolation of microbes that are present in source material in very low numbers?

Answer 65

Enrichment culture

Question 66

Who developed enrichment culture?

Answer 66

Martinus Beijerinck

Question 67

How does enrichment culture work?

Answer 67

A small amount of sample is placed in a liquid medium designed for certain types of organisms; those that grow the fastest increase in proportion to those that grow slowly or not at all; after growth, the resulting population - with its altered ratios - is plated on solid medium, and various different major types are identified

Question 68

What is the only necessity for performing enrichment culture?

Answer 68

The ability to devise a liquid medium that selectively favors a particular type of organism

Question 69

What are four microbes that have become model systems for the study of cell biology, molecular genetics, and development?

Answer 69

1. Escherichia coli
2. Bacillus subtilis
3. Caulobacter crescentus
4. Saccharomyces cerevisiae

Question 70

Which model organism is the best studied?

Answer 70

Escherichia coli

Question 71

Is Escherichia coli gram-positive or gram-negative?

Answer 71

Gram-negative

Question 72

Which model organism is a bacterial inhabitant of soil and water with a long stalk at one end that is often used to study cell morphology as it divides asymmetrically to produce two different daughter cells?

Answer 72

Caulobacter crescentus

Question 73

Which model organism is a common soil bacterium that produces a dormant endospore when starved and has been useful in stodying genetics and differentiation?

Answer 73

Bacillus subtilis

Question 74

Which model organism is a yeast, a unicellular fungus, and the most common eukaroytic microbial experimental system?

Answer 74

Saccharomyces cerevisiae

Question 75

What organism is this?

Answer 75

Escherichia coli

Question 76

What organism is pictured?

Question 77

What organism is pictured?

Answer 77

Bacillus subtilis

Question 78

What organism is pictured?

Answer 78

Saccharomyces cervisiae