7/30/2019 Chapt01 SSG

1/11

Part I INTRODUCTION TO MICROBIOLOGY

1 The Evolution of Microorganisms andMicrobiology

CHAPTER OVERVIEW

This chapter introduces the field of microbiology and discusses the importance ofmicroorganisms not only as causative agents of disease, but also as importantcontributors to food production, antibiotic manufacture, vaccine development, andenvironmental management. It presents a brief history of the science of microbiology

and an overview of the microbial world. The origin of life and microbial evolution is putin the context of microbial phylogenies.

CHAPTER OBJECTIVES

After reading this chapter you should be able to:

define the science of microbiology and describe some of the general methodsused in the study of microorganisms

discuss the historical concept of spontaneous generation and the experiments thatwere performed to disprove this erroneous idea

discuss how Kochs postulates are used to establish the causal link between asuspected microorganism and a disease

describe some of the various activities of microorganisms that are beneficial tohumans

describe prokaryotic and eukaryotic morphology and the distribution ofmicroorganisms among the three domains in which living organisms arecategorized

discuss the origin of life, the RNA world, and the evolution of microorganisms

CHAPTER OUTLINE

I.MicrobiologyIntroduction

A. Microbes are found everywhere and are indispensable for cycling of essentialelements on earth

B.Most microbes are beneficial to society by producing foods, oxygen, andcommercial products, and by enhancing human health; some microbes causedisease

II.Members of the Microbial WorldA. Microbiology is the study of organisms too small to be clearly seen by the

unaided eye (i.e., microorganisms); these include viruses, bacteria,archaea, protozoa, algae, and fungi

1

7/30/2019 Chapt01 SSG

2/11

B. Some microbes (e.g., algae and fungi) are large enough to be visible, butare still included in the field of microbiology; while these may bemulticellular organisms, differentiated tissues are absent

C. Prokaryotes have a relatively simple morphology and lack a true membrane-delimited nucleus

D. Eukaryotes are morphologically complex and have a true, membrane-

enclosed nucleusE. The work of Carl Woese and his collaborators suggests that organisms fall intoone of three domains based on nucleotide sequence similarities among smallsubunit ribosomal RNAs (SSU rRNAs)

1. Eukaryacontains all eukaryotic organisms; have a complexmembrane-delimited organelle structure

2. Bacteriadiverse and widespread prokaryotes; cell walls containpeptidoglycan

3. Archaeaprokaryotes with cell walls that lack peptidoglycan; have uniquemembrane lipids

F. Viruses, viroids, virusoids, and prions are not composed of cells and not partof the domain classification scheme

III. Microbial EvolutionA. Evidence for the origin of life

1. Earth is about 4.6 billion years old; what appear to be the fossilizedremains of 3.5-billion-year-old prokaryotic cells have been found instromatolites and sedimentary rocks

2. Extant organisms have been suggested to contain structures andmolecules that are relics of ancient life forms

B. RNA world1. It is speculated in the RNA world theory that the first self-replicating

molecules were RNAs that stored information and had catalytic activity(ribozymes); eventually DNA became the molecule for information storageand proteins became the molecules with catalytic activity

2. The earliest prokaryotes were probably anaerobic and lithotrophs

3.Cyanobacteria probably developed oxygenic photosynthesis 2.5 billion years agoforming layered rocks called stromatolites (stratified rocks that are formed by

incorporation of mineral sediments into microbial mats)C. Evolution of the three domains of life1. The universal phylogenetic tree is based on comparisons of small subunit rRNAmolecules such that evolutionary distances are shown2. The last universal common ancestor (LUCA) sits at the root of the tree on thebacterial branch; the nature of this organism is unclear

3. The endosymbiotic origin of mitochondria, chloroplasts, andhydrogenosomesa. Endosymbiotic theory states that these organelles arose from

prokaryotes that lived within eukaryotic cells, eventually losing partsof their genome to the host cell and thereby losing the ability to

survive independently; organelles have both circular chromosomesrelated to bacterial genomes and independent transcription andtranslation systems

b. The hydrogen hypothesis states that the progenitor of mitochondriawas a bacterium that produced hydrogen through fermentation thatwas required by the host; the hydrogenosome may be another relic ofthis early symbiont

4. Cellular life forms developed through the same evolutionary processesseen today including mutation and horizontal gene transfer

2

7/30/2019 Chapt01 SSG

3/11

5. Since prokaryotic organisms generally do not reproduce sexually, speciesare defined as groups of strains (pure cultures) sharing stabledistinguishing properties; microbiologists use the binomial system fornaming species

IV. Microbiology and Its OriginsA. Microscopy and the discovery of microorganisms

1. Invisible living creatures were thought to exist and were thought to beresponsible for disease long before they were observed; the field ofmicrobiology developed as the tools used to study microbesdeveloped

2. Antony van Leeuwenhoek (16321723) constructed microscopes andis credited as the first person to observe and describemicroorganisms accurately; Robert Hooke published the first drawingsof microorganisms

B. Culture-based methods for studying microorganisms1. Spontaneous generationa. The proponents of the concept of spontaneous generation claimed

that living organisms could develop from nonliving or decomposingmatter

b. Francesco Redi (16261697) challenged this concept by showing thatmaggots on decaying meat came from fly eggs deposited on themeat, and not from the meat itself

c. John Needham (17131781) showed that mutton broth boiled in flasksand then sealed could still develop microorganisms, which supportedthe theory of spontaneous generation

d. Lazzaro Spallanzani (17291799) showed that flasks sealed and thenboiled had no growth of microorganisms, and he proposed that aircarried germs to the culture medium; he also commented thatexternal air might be needed to support the growth of animalsalready in the medium; the latter concept was appealing tosupporters of spontaneous generation

e. Theodore Schwann (18101882) and others carried out experiments

testing the need for air if growth was to occurf. Louis Pasteur (18221895) heated the necks of flasks, drawing themout into long curves, sterilized the media, and left the flasks open tothe air; no growth was observed because particles carrying organismsdid not reach the medium, instead they were trapped in the neck ofthe flask; if the necks were broken, particles would enter the flasksand the organisms would grow; in this way Pasteur disproved thetheory of spontaneous generation

g. John Tyndall (18201893) demonstrated that dust carried microbesand that if dust was absent, the broth remained sterileeven if it wasdirectly exposed to air; Tyndall also provided evidence for theexistence of heat-resistant forms of bacteria

C. Microorganisms and disease

1. Agostino Bassi (17731856) showed that a silkworm disease was causedby a fungus, the first demonstration of microbes causing disease2. Louis Pasteur showed that the pbrine disease of silkworms was caused by

a protozoan parasite; he demonstrated that alcoholic fermentations wereperformed by yeasts under anaerobic conditions and that differentfermentation products were produced by different microorganisms; hedeveloped the process of pasteurization used to preserve wine and milkduring storage

3

7/30/2019 Chapt01 SSG

4/11

3. Joseph Lister (18721912) developed a system of surgery designed toprevent microorganisms from entering wounds; his patients had fewerpostoperative infections, thereby providing indirect evidence thatmicroorganisms were the causal agents of human disease; his publishedfindings transformed the practice of surgery

D. Koch's postulates1.

Robert Koch (18431910), using criteria developed by his teacher, JacobHenle (18091895), established the relationship between Bacillusanthracis and anthrax; his criteria became known as Kochs postulatesand are still used to establish the link between a particular microorganismand a particular disease:a. The microorganism must be present in every case of the disease, but

absent from healthy individualsb. The suspected microorganism must be isolated and grown in pure

culturec. The same disease must result when the isolated microorganism is

inoculated into a healthy hostd. The same microorganism must be isolated again from the diseased

host

2. Kochs work with anthrax was independently confirmed by PasteurE. Pure culture methods1. Koch and his associates developed techniques, reagents, and other

materials for culturing bacterial pathogens on solid growth media; agarplates enable microbiologists to isolate microbes in pure culture

2. Charles Chamberland (18511908) constructed a bacterial filter thatremoved bacteria and larger microbes from specimens; this led to thediscovery of viruses as disease-causing agents

F. Immunology1. Edward Jenner used a vaccination procedure to protect individuals from

smallpox2. Louis Pasteur developed other vaccines including those for chicken

cholera, anthrax, and rabies

3. Emil von Behring (18541917) and Shibasaburo Kitasato (18521931)induced the formation of diphtheria-toxin antitoxins in rabbits; theantitoxins (actually antibodies) were effectively used to treat humans andprovided evidence for humoral (antibody) immunity

4. Elie Metchnikoff (18451916) described phagocytic cells in the blood, thusdemonstrating cell-mediated immunity

G. Microbial ecology1. Sergei Winogradsky (18561953) worked with soil bacteria and

discovered that they could oxidize iron, sulfur, and ammonia to obtainenergy; he also studied anaerobic nitrogen fixation and cellulosedecomposition

2. Martinus Beijerinck (18511931) isolated aerobic nitrogen-fixing bacteria,a root-nodule bacterium capable of fixing nitrogen, and sulfate-reducing

bacteria3. Beijerinck and Winogradsky pioneered the use of enrichment cultures andselective media to isolate microorganisms that can eat and/or breatheinorganic minerals

V.Microbiology TodayA. Research in both basic and applied microbiology has an impact on many fields

including medicine, agriculture, food science, ecology, genetics, biochemistry,and molecular biologyB. Molecular and genomic methods of studying microbes

4

7/30/2019 Chapt01 SSG

5/11

1. Manipulating DNA in microorganisms is central to studying theirrelationships and nature

2. The genome (all the genetic information) of an organism can beanalyzed using methods leading to determination of the basesequence of genes

3. Genomic analysis defines functions of genes, their regulation, and

how they form biological systemsC. Major fields in microbiology1. Medical microbiology - the study of infectious disease in humans and

animals, identifying the causative agents and planning measures fortheir control

2. Public health microbiology and epidemiology - the study of themechanisms by which diseases spread and the monitoring of theamount of disease in populations

3. Immunology - study of how the body's immune system protectsagainst infectious disease; includes the study of allergies andautoimmune diseases

4. Microbial ecology - study of the ecological role of microbes inbiogeochemical cycles and the interaction of microbes with each

other and their habitat5. Agricultural microbiology - study of the impact of microbes onagriculture, including aspects of nutrient cycles, animal husbandry,and plant pathogens

6. Food and dairy microbiology - study of the use of microbes in foodproduction, food spoilage, and food-borne diseases

7. Industrial microbiology - study of the use of microorganisms in themanufacture of antibiotics, vaccines, chemicals, enzymes, vitamins,and other products

D. More basic research fields of microbiology include microbial physiology,microbial genetics, molecular biology, and bioinformatics

TERMS AND DEFINITIONS

____ 1. Study of organisms too small to be individually observed with the unaided eye____ 2. Organisms composed of many different cells____ 3. Microorganisms with cells that do not contain a nucleus____ 4. A class of acellular microbes that are infectious agents____ 5. Organisms with cells that contain a nucleus____ 6. Rocklike structures formed by ancient microbial mats of cyanobacteria____ 7. Organisms that are present in the biosphere today____ 8. Molecules of RNA that have enzymatic activity____ 9. Microbes that use inorganic chemicals as electron sources____ 10. Organisms that cannot grow in the presence of oxygen____ 11. The root of the phylogenetic tree that is the progenitor of all currentorganisms

____ 12. The currently accepted explanation of how the organelles mitochondria,chloroplasts, and hydrogenosomes arose

____ 13. An experimental scheme used to demonstrate the causative agent of aninfectious disease

____ 14. A research tool that allows microbial isolates to be grown and separated____ 15. All of the DNA in a cell

a. agar platesb. anaerobes

5

7/30/2019 Chapt01 SSG

6/11

c. endosymbiotic theoryd. eukaryotese. extant organismsf. genomeg. Koch's postulatesh. last universal common ancestor

i. lithotrophsj. microbiologyk. multicellularl. prokaryotesm. ribozymesn. stromatoliteso. viruses

AREAS OF MICROBIOLOGY

From the list below, select the area that best matches the description in each of thenumbered statements.

____ 1. Deals with diseases of humans and animals____ 2. Endeavors to control the spread of communicable diseases____ 3. Deals with the mechanisms by which the human body protects itself from

disease-causing organisms____ 4. Deals with microorganisms that cause damage to crops or live in herds of

domestic animals; also deals with ways of increasing soil fertility____ 5. Studies the relationship between microorganisms and their habitats____ 6. Investigates the causes of spoilage of products for human consumption and

the use of microorganisms in the production of cheese, yogurt, pickles, beer,etc.

____ 7. Employs microorganisms to make products such as antibiotics, vaccines,steroids, alcohols, vitamins, amino acids, and enzymes

____ 8. Investigates the synthesis of antibiotics and toxins, microbial energy

production, the ways in which microorganisms survive harsh environmentalconditions, etc.

____ 9. Focuses on the nature of genetic information and how genes regulate thedevelopment and function of cells and organisms

____10. Involves the insertion of new genes into organisms in order to investigate thegenes functions or to produce useful organisms with new properties

a. agricultural microbiologyb. food and dairy microbiologyc. genetic engineeringd. immunologye. industrial microbiologyf. medical microbiology

g. microbial ecologyh. microbial physiologyi. molecular biology

j. public health microbiology

FILL IN THE BLANK

1. The concept that living organisms could develop from nonliving or decomposingmatter is referred to as

6

7/30/2019 Chapt01 SSG

7/11

. An Italian physician named ____________ challenged thisby showing that maggots developed from fly eggs, not from decaying meat as hadpreviously been thought. However, even after this, many thought that simplemicroorganisms could develop from nonliving material, even if more complexorganisms could not. This was finally disproved by the work of a French scientistnamed ____________ and an English physicist named ____________, who both

demonstrated that organisms only developed in sterile broth exposed to air if dustparticles carrying living organisms dropped into the broth.2. Indirect evidence that microorganisms were agents of human disease came from

the work of an English surgeon named ____________, who developed a procedurefor antiseptic surgery in which he heat-sterilized his surgical instruments beforeuse and also sprayed the compound phenol, which kills bacteria, over the surgicalarea. These procedures lowered the incidence of postoperative infections.

3. and discovered that older cultures of the bacterium that caused chicken choleralost their ability to cause disease, or were said to be ____________. If chickens wereinjected with these older strains, they remained healthy but developed the abilityto resist disease. They called this culture a ____________ in honor of the Englishphysician ______________, who developed the procedure in order to protect againstsmallpox.

4. Inactivated toxin from the microorganism that causes diphtheria was injected intorabbits by ____________ and ____________, inducing the rabbits to produce a solublesubstance in the blood that would neutralize the toxin and protect against disease.

This is referred to as ____________ immunity. Taking a different approach, ElieMetchnikoff discovered that some blood cells were capable of ingesting bacteriaand thereby destroying them. He called this process ____________, and the cellsthat can do this, ____________. This is the basis for cell-mediated immunity.

5. The theory that yeast cells were responsible for converting sugar to alcohol wasfirst proposed by ____________ and others. However, it was ____________ who did thedefinitive work that clearly demonstrated this to be true. One of his mostimportant discoveries was that some organisms carried out these processes

____________ (in the presence of oxygen) while others carried them out ____________(in the absence of oxygen).

6. Two of the most important contributors in the field of microbial ecology were____________, who discovered that soil bacteria could oxidize iron, sulfur, andammonia to obtain energy, and ____________, who isolated a root-nodule bacteriumcapable of nitrogen fixation. These individuals also pioneered the use of

____________ __________ techniques and __________ media.7. Scientists begin their attempts to understand natural phenomena by gathering

observations on a topic and then formulating an , which issubsequently tested experimentally. If this initial educated guess about thephenomenon of interest survives the testing, it may become a , which isa set of propositions and concepts that provides a reliable, systematic, andrigorous account of an aspect of nature.

8.The two prokaryotic domains are and , while plants andanimals are in the domain .

MULTIPLE CHOICE

For each of the questions below select the one bestanswer.

1. Which of the following is (are) usedto define the field of microbiology?a. the size of the organism

studied

b. the techniques employed inthe study of organismsregardless of their size

c. Both (a) and (b) are correct.

7

7/30/2019 Chapt01 SSG

8/11

d. Neither (a) nor (b) is correct. 2. Which of the following developed aset of criteria that could be used toestablish a causative link betweena particular microorganism and aparticular disease?a. van Leeuwenhoek

b. Fracastoroc. Pasteurd. Koch

8

7/30/2019 Chapt01 SSG

9/11

3. Which of the following was the firstto observe and accurately describemicroorganisms?a. van Leeuwenhoekb. Fracastoroc. Pasteur

d. Koch4. Which of the following providedstrong evidence against theconcept of spontaneousgeneration?a. van Leeuwenhoekb. Fracastoroc. Pasteurd. Koch

5. Which of the following providedevidence that a microorganismcould be responsible for aparticular disease?a. Bassib. Berkeley

c. Kochd. All of the above are correct.

6. Which of the following has beensuggested as the central moleculein the precellular stage of life'sorigins?a. DNAb. Proteinsc. RNAd. Lipids

TRUE/FALSE

____ 1. Although Robert Koch used and published the criteria for establishing acausative link between a particular microorganism and a particular disease,the criteria were actually first developed by his former teacher, Jacob Henle.

____ 2. The major difference between prokaryotic cells and eukaryotic cells is thateukaryotic cells have a membrane-bound nucleus but prokaryotic cells do not.

____ 3. Agar is used instead of gelatin to solidify microbial media because agar is notdigested by many bacteria while gelatin is.

____ 4. The first disease to be identified as being caused by a virus was anthrax.____ 5. The discovery of viruses and their role in disease was made possible when

Charles Chamberland constructed a porcelain filter that would retain bacteria.Using these filters, others found that some disease-causing organisms werenot retained by the filter; these were referred to as viruses.

____ 6. Louis Pasteur was the first to document the use of a vaccination procedure toprevent disease.

____ 7. Microorganisms can be used in bioremediation to reduce pollution effects.____ 8. Genetically engineered microorganisms are used to produce a variety of

products including hormones, antibiotics, and vaccines.____ 9. Recent advances in classification led to the proposal that organisms should be

divided into three domains:Archaea, Bacteria, and Eukarya.

CRITICAL THINKING

1. Discuss the spontaneous generation theory. Present the evidence that was used to

support it and present the evidence that was used to discredit it. How was thistheory finally discredited?

9

7/30/2019 Chapt01 SSG

10/11

2. Describe in detail at least two ways in which microorganisms have a direct andsubstantial impact on your life (other than as causative agents of disease). Includea discussion of the role(s) of the microorganisms in these processes.

3. In the 1980s when AIDS was first recognized, scientists were faced with the task ofidentifying the causative agent. Suppose you were one of those scientists and thatyou observed a virus in the tissues of AIDS patients. Which steps of Kochspostulate could you use to support your belief that the virus was responsible forthe disease? Which steps couldnt you use? Explain your answers.

ANSWER KEY

Terms and Definitions

1. j, 2. k, 3. l, 4. o, 5. d, 6. n, 7. e, 8. m, 9. i, 10. b, 11. h, 12. c, 13. g, 14. a, 15. f

Areas of Microbiology

1. f, 2. j, 3. d, 4. a, 5. g, 6. b, 7. e, 8. h, 9. i, 10. c

Fill in the Blank

1. spontaneous generation; Francesco Redi; Louis Pasteur; John Tyndall 2. Joseph Lister3. Pasteur; Roux; attenuated; vaccine; Jenner 4. Emil von Behring; Shibasaburo

Kitasato; humoral; phagocytosis; phagocytes5. Theodore Schwann; Louis Pasteur; aerobically; anaerobically 6. SergiusWinogradsky; Martinus Beijerinck; enrichment culture; selective 7. hypothesis; theory8. Bacteria; Archaea; Eukarya

Multiple Choice

1. c, 2. d, 3. a, 4. c, 5. d, 6. c

10

7/30/2019 Chapt01 SSG

11/11

True/False

1. T, 2. T, 3. T, 4. F, 5. T, 6. F, 7. T, 8. T, 9. T

11