Prescott Home   Microbiology, 4/e               Prescott, Harley, Klein
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1 The History and Scope of Microbiology

 

CHAPTER OVERVIEW

This chapter introduces the field of microbiology and discusses the importance of microorganisms not only as causative agents of disease but also as important contributors to food production, antibiotic manufacture, vaccine development, and environmental management. It presents a brief history of the science of microbiology, an overview of the microbial world, and a discussion of the scope and relevance of microbiology in today=s society.

 

CHAPTER OBJECTIVES

After reading this chapter you should be able to:

! define the science of microbiology and describe some of the general methods used in the study of microorganisms

! discuss the historical concept of spontaneous generation and the experiments that were performed to disprove this erroneous idea

! discuss Koch=s postulates, which are used to establish the causal link between a suspected microorganism and a disease

! describe some of the various nonpathological activities of microorganisms

! describe procaryotic and eucaryotic morphology, the two types of cellular anatomy, and also the distribution of microorganisms among the various kingdoms or domains in which living organisms are categorized

! discuss the importance of the field of microbiology to other areas of biology and to general human welfare

 

CHAPTER OUTLINE

I. The Discovery of Microorganisms

A. Microbiology is the study of organisms too small to be clearly seen by the unaided eye (i.e., microorganisms)

B. Types of microorganisms include viruses, bacteria, protozoa, algae, and fungi

1. Some algae and fungi are large enough to be visible, but are included in the field of microbiology because they have similar properties and because similar techniques are employed to study them (isolation, sterilization, culture in artificial media)

C. Early discovery of microorganisms

1. Invisible living creatures were thought to exist and were thought to be responsible for disease long before they were observed

2. Antony van Leeuwenhoek (1632B1723) constructed microscopes and was the first person to observe and describe microorganisms accurately

II. The Spontaneous Generation Conflict

A. The proponents of the concept of spontaneous generation claimed that living organisms could develop from nonliving or decomposing matter

B. Francesco Redi (1626B1697) challenged this concept by showing that maggots on decaying meat came from fly eggs deposited on the meat, and not from the meat itself

C. John Needham (1713B1781) showed that mutton broth boiled in flasks and then sealed could still develop microorganisms, which supported the theory of spontaneous generation

D. Lazzaro Spallanzani (1729B1799) showed that flasks sealed and then boiled had no growth of microorganisms, and he proposed that air carried germs to the culture medium; he also commented that external air might be needed to support the growth of animals already in the medium; the latter concept was appealing to supporters of spontaneous generation

E. Louis Pasteur (1822B1895) trapped airborne organisms in cotton; he also heated the necks of flasks, drawing them out into long curves, sterilized the media, and left the flasks open to the air; no growth was observed because dust particles carrying organisms did not reach the medium, instead they were trapped in the neck of the flask; if the necks were broken, dust would settle and the organisms would grow; in this way Pasteur disproved the theory of spontaneous generation

F. John Tyndall (1820B1893) demonstrated that dust did carry microbes and that if dust was absent, the broth remained sterileCeven if it was directly exposed to air; Tyndall also provided evidence for the existence of heat-resistant forms of bacteria

III. The Recognition of the Microbial Role in Disease

A. Agostino Bassi (1773B1856) showed that a silkworm disease was caused by a fungus

B. M. J. Berkeley (ca. 1845) demonstrated that the Great Potato Blight of Ireland was caused by a fungus

C. Louis Pasteur showed that the pébrine disease of silkworms was caused by a protozoan parasite

D. Joseph Lister (1872B1912) developed a system of surgery designed to prevent microorganisms from entering wounds; his patients had fewer postoperative infections, thereby providing indirect evidence that microorganisms were the causal agents of human disease; his published findings (1867) transformed the practice of surgery

E. Robert Koch (1843B1910), using criteria developed by his teacher, Jacob Henle (1809-1895), established the relationship between Bacillus anthracis and anthrax; his criteria became known as Koch=s Postulates and are still used to establish the link between a particular microorganism and a particular disease:

1. The microorganisms must be present in every case of the disease but absent from healthy individuals

2. The suspected microorganisms must be isolated and grown in pure culture

3. The same disease must result when the isolated microorganism is inoculated into a healthy host

4. The same microorganism must be isolated again from the diseased host

F. Koch=s work was independently confirmed by Pasteur

G. Charles Chamberland (1851B1908) was instrumental in identifying viruses as disease-causing agents

H. Edward Jenner (ca. 1798) used a vaccination procedure to protect individuals from smallpox

I. Louis Pasteur developed other vaccines including those for chicken cholera, anthrax, and rabies

J. Emil von Behring (1854B1917) and Shibasaburo Kitasato (1852B1931) induced the formation of diphtheria tetanus antitoxins in rabbits which were effectively used to treat humans thus demonstrating humoral immunity

K. Elie Metchnikoff (1845B1916) demonstrated the existence of phagocytic cells in the blood, thus demonstrating cell-mediated immunity

IV. The Discovery of Microbial Effects on Organic and Inorganic Matter

A. Louis Pasteur demonstrated that alcoholic fermentations were the result of microbial activity, that some organisms could decrease alcohol yield and sour the product, and that some fermentations were aerobic and some anaerobic; he also developed the process of pasteurization (see chapter 7) to preserve wine during storage

B. Sergei Winogradsky (1856B1953) worked with soil bacteria and discovered that they could oxidize iron, sulfur, and ammonia to obtain energy; he also studied anaerobic nitrogen-fixation and cellulose decomposition

C. Martinus Beijerinck (1851B1931) isolated aerobic nitrogen-fixing bacteria and sulfate reducing bacteria

D. Beijerinck and Winogradsky pioneered the use of enrichment cultures and selective media

V. The Development of Microbiology in This Century

A. Microbiology established a closer relationship with other disciplines during the 1940s because of its association with genetics and biochemistry

B. George W. Beadle and Edward L. Tatum (ca. 1941) studied the relationship between genes and enzymes using the bread mold, Neurospora

C. Salvadore Luria and Max Delbruck (ca. 1943) showed that mutations were spontaneous and not directed by the environment

D. Oswald T. Avery, Colin M. MacLeod, and Maclyn McCarty (1944) provided evidence that deoxyribonucleic acid (DNA) was the genetic material and carried genetic information during transformation (see chapter 13)

E. More recently, microbiology has been a major contributor to molecular biology and has been deeply involved in the elucidation of the genetic code; in studies on the mechanisms of DNA, ribonucleic acid (RNA), and protein synthesis; and in studies on the regulation of gene expression and the control of enzyme activity

F. In the 1970s new discoveries in microbiology led to the development of recombinant DNA technology and genetic engineering

VI. The Composition of the Microbial World

A. Procaryotes have a relatively simple morphology and lack a true membrane-delimited nucleus

B. Eucaryotes are morphologically complex and have a true, membrane-enclosed nucleus

C. Organisms are currently divided in five kingdoms: the Monera or Procaryotae, Protista, Fungi, Animalia, and Plantae

D. Alternative classification schemes involving several empires or domains with multiple kingdoms contained within have been proposed and are discussed in chapter 19

E. Microbiologists are concerned primarily with members of the first three kingdoms and also with viruses, which are not classified with living organisms

VII. The Scope and Relevance of Microbiology

A. Microorganisms were the first living organisms on the planet, live everywhere life is possible, are more numerous than any other kind of organism, and probably constitute the largest component of the earth=s biomass

B. The entire ecosystem depends on the activities of microorganisms, and microorganisms influence human society in countless ways

C. Microbiology has an impact on medicine, agriculture, food science, ecology, genetics, biochemistry, and other fields

D. Microbiologists may be interested in specific types of organisms:

1. VirologistsCviruses

2. BacteriologistsCbacteria

3. Phycologists or AlgologistsCalgae

4. MycologistsCfungi

5. ProtozoologistsCprotozoa

E. Microbiologists may be interested in various characteristics or activities of microorganisms:

1. Microbial morphology

2. Microbial cytology

3. Microbial physiology

4. Microbial ecology

5. Microbial genetics and molecular biology

6. Microbial taxonomy

F. Microbiologists may have a more applied focus:

1. Medical microbiology, including immunology

2. Food and dairy microbiology

3. Public health microbiology

4. Industrial microbiology

5. Agricultural microbiology

 

 

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