The Main Themes of Microbiology

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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 magnification
• Such microscopic organisms are collectively
  referred to as microorganisms or microbes
• Microorganisms 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
  disciplines
• Microbiologists 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

• Immunology
• Public health microbiology and epidemiology
• Food, dairy and aquatic microbiology
• Agricultural microbiology
• Biotechnology
• Genetic engineering and recombinant DNA technology

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Specialty Professions of Microbiology

• Geomicrobiologists - focus on the roles of
  microbes in the development of earths crust
• Marine microbiologists - study the oceans and its
  smallest inhabitants
• Pharmaceutical microbiologists - discover and
  develop new drugs from microbial sources
• Nurse epidemiologists - analyze the occurrence of
  infectious diseases in hospitals
• Astrobiologists - 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 earths habitats
  and the evolution of other life forms
• Procaryotes (no nucleus) appeared first
• Eucaryotes (with nucleus) appeared later
• Microbes can be found nearly everywhere, from the
  deep in the earths 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 earths ecosystems
• Decomposition and nutrient recycling
• Biotechnology
• production of foods, drugs and vaccines
• Genetic engineering
• Bioremediation
• Infectious 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
  - pathogens
• Infectious 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 1.7 measurements
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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
  beneficial
• A free-living organism can derive all required
  foods and other factors directly from a nonliving
  environment
• Many microorganisms have close associations with
  other organisms
• parasites - harbored and nourished in the bodies
  of larger organisms called hosts
• a parasites 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
  microbiologists
• Prominent 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 merchant
• First to observe living microbes
• Single-lens magnified up to 300X

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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
  phenomenon
• Form a hypothesis - a tentative explanation that
  can be supported or refuted by observation and
  experimentation
• A 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
  investigators
• If hypothesis is supported by a growing body of
  evidence and survives rigorous scrutiny, it moves
  to the next level of confidence - it becomes a
  theory
• If 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 hospital
• Dr. 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 spoilage
• Disproved spontaneous generation of
  microorganisms
• Developed pasteurization
• Demonstrated what is now known as Germ Theory of
  Disease
• Developed a rabies vaccine

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Robert Koch (1843-1910)

• Established Kochs postulates - a sequence of
  experimental steps that verified the germ theory
• Identified cause of anthrax, TB, and cholera
• Developed pure culture methods

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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 Eukarya
• Kingdom -
• Phylum or Division
• Class
• Order
• Family
• Genus
• species

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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 lost
• All new species originate from preexisting
  species
• Closely related organisms have similar features
  because they evolved from common ancestral forms
• Evolution usually progresses toward greater
  complexity

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3 Domains

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

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Insert figure 1.15 Woese-Fox System