Chapter 1

The Main Themes of Microbiology

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Microbiology

Microbiology is a specialized area of biology that deals with living organisms ordinarily too small to be seen without magnificationSuch microscopic organisms are collectively referred to as microorganisms or microbesMicroorganisms include:

bacteria viruses fungi (microscopic, fungal spores) protozoa (unicellular) helminths (parasitic worms) algae

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Microbiology

Microbiology is one of the largest and most complex of the biological sciences because it integrates subject matter from many diverse disciplinesMicrobiologists study every aspect of microbes

their genetics their physiology characteristics that may be harmful or beneficial the ways they interact with the environment and with

their hosts their uses in industry and agriculture

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Microbiological Endeavors-A sampler

ImmunologyPublic health microbiology and epidemiologyFood, dairy and aquatic microbiologyAgricultural microbiologyBiotechnologyGenetic engineering and recombinant DNA technology

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Specialty Professions of Microbiology

Geomicrobiologists - focus on the roles of microbes in the development of earth’s crustMarine microbiologists - study the oceans and its smallest inhabitantsPharmaceutical microbiologists - discover and develop new drugs from microbial sourcesNurse epidemiologists - analyze the occurrence of infectious diseases in hospitalsAstrobiologists - study the possibilities of organisms in space

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The Impact of Microbes on Earth

For billions of years, microbes have extensively shaped the development of the earth’s habitats and the evolution of other life formsProcaryotes (no nucleus) appeared firstEucaryotes (with nucleus) appeared laterMicrobes can be found nearly everywhere, from the deep in the earth’s crust, to the polar ice caps and oceans, to the bodies of plants and animals

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Microbial Involvement

Nutrient production (photosynthesis)Energy flow through the earth’s ecosystemsDecomposition and nutrient recyclingBiotechnology

production of foods, drugs and vaccines

Genetic engineeringBioremediationInfectious diseases

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Infectious Diseases and the Human Condition

Humanity is plagued by nearly 2,000 different microbes that can cause various types of diseases - pathogensInfectious diseases still devastate human populations worldwide, despite significant strides in understanding and treating them 10 B new infections/year worldwide (WHO)12 M deaths from infections/year worldwide

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The General Characteristics of Microorganisms

Prokaryotes and eukaryotes prokaryote – microscopic, unicellular organisms, lack

nuclei and membrane-bound organelles eukaryote – unicellular (microscopic) and multicellular,

nucleus and membrane-bound organelles

Viruses acellular, parasitic particles composed of a nucleic acid

and protein

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Microbial Dimensions

Prokaryotes are measured in micrometers (10-6 m)Viruses in nanometers (10-9 m) Helminths are measured in millimeters (10-3 m)

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Insert figure 1.7measurements

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Lifestyles of Microorganisms

The majority of microorganisms live a free existence in habitats such as soil and water, where they are relatively harmless and often beneficialA free-living organism can derive all required foods and other factors directly from a nonliving environmentMany microorganisms have close associations with other organisms

parasites - harbored and nourished in the bodies of larger organisms called hosts

a parasite’s actions may cause damage to its host through infection and disease

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Historical Foundations of Microbiology

300 years of contributions by many microbiologistsProminent discoveries include:

microscopy The rise of the scientific method development of medical microbiology germ theory modern microbiological techniques

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Antonie van Leeuwenhoek (1632-1723)

Dutch linen merchantFirst to observe living microbesSingle-lens magnified up to 300X

Insert figure 1.8

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Insert figure 1.9 (a)microscope

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Spontaneous Generation

Early belief that some forms of life could arise from vital forces present in nonliving or decomposing matter (flies from rotten meat, mushrooms on rotting tree, rats and mice from piles of litter. etc)

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Scientific Method

A general approach to explain a natural phenomenonForm a hypothesis - a tentative explanation that can be supported or refuted by observation and experimentationA lengthy process of experimentation, analysis and testing either supports or refutes the hypothesis

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Scientific Method

Results must be published and repeated by other investigatorsIf hypothesis is supported by a growing body of evidence and survives rigorous scrutiny, it moves to the next level of confidence - it becomes a theoryIf evidence of a theory is so compelling that the next level of confidence is reached - it becomes a Law or principle

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Discovery of Spores and Sterilization

John Tyndall and Ferdinand Cohn each demonstrated the presence of heat resistant forms of some microbes

Cohn determined these forms to be endospores

Sterility requires the elimination of all life forms including endospores and viruses

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Development of Aseptic Techniques

Dr. Oliver Wendell Holmes – observed that mothers of home births had fewer infections than those who gave birth in hospitalDr. Ignaz Semmelweis – correlated infections with physicians coming directly from autopsy room to maternity ward

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Development of Aseptic Techniques

Joseph Lister – introduced aseptic techniques reducing microbes in medical settings to prevent infections

involved disinfection of hands using chemicals prior to surgery

use of heat for sterilization

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Pathogens and Germ Theory of Disease

Many diseases are caused by the growth of microbes in the body and not by sins, bad character, or poverty, etc.Two major contributors:

Louis Pasteur and Robert Koch

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Louis Pasteur (1822-1895)

Showed microbes caused fermentation and spoilageDisproved spontaneous generation of microorganismsDeveloped pasteurizationDemonstrated what is now known as Germ Theory of Disease Developed a rabies vaccine

Insert figure 1.11

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Robert Koch (1843-1910)

Established Koch’s postulates - a sequence of experimental steps that verified the germ theory

Identified cause of anthrax, TB, and choleraDeveloped pure culture methodsInsert figure 1.12

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Taxonomy: Organizing, Classifying and Naming Living Things

Formal system originated by Carl von Linné (1701-1778) Concerned with:

classification – orderly arrangement of organisms into groups

nomenclature – assigning names identification – discovering and recording traits of

organisms for placement into taxonomic schemes

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Levels of Classification

Domain - Archaea, Bacteria & EukaryaKingdom - Phylum or DivisionClass OrderFamilyGenusspecies

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Naming Microrganisms

Binomial (scientific) nomenclature Gives each microbe 2 names:

Genus - noun, always capitalized species - adjective, lowercase

Both italicized or underlined Staphylococcus aureus (S. aureus) Bacillus subtilis (B. subtilis) Escherichia coli (E. coli)

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Evolution - living things change gradually over millions of years

Changes favoring survival are retained and less beneficial changes are lostAll new species originate from preexisting speciesClosely related organisms have similar features because they evolved from common ancestral formsEvolution usually progresses toward greater complexity

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3 Domains

Bacteria - true bacteria, peptidoglycanArchaea - odd bacteria that live in extreme environments, high salt, heat, etc.Eukarya- have a nucleus and organelles

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Insert figure 1.15Woese-Fox System