Lecture 1 Introduction, History and Microscopy - PowerPoint

							                 Lecture 1

Introduction, History
     and Microscopy




Text Chapters: 1.1-1.8; 4.1-4.3
Introduction to Microbiology

 • What is Microbiology?


 • What do we know about Microbiology?
 • Group task (Let’s have fun discussion!!)
   :3-4 students sit as a group and discuss about
   microbiology and fill in the worksheet with any
   words starting with given alphabet.
Introduction: Definitions

  • Microorganisms
     – Organisms that are distinct form macroorganisms
     – Diverse group
     – Exist as single cells (unicellular) or in cell clusters
       (multicellular)


  • Microbiology
     – The basic science of understanding microbial life
     – The applications of science to human needs.
Introduction: The importance of Microbiology


   • Microorganisms are excellent models for
     understanding cell function in higher
     organisms, including humans.

   • Because microorganisms are central to the
     very functioning of the biosphere, the
     science of microbiology is the foundation of
     all the biological sciences
Introduction: Examples for Microorganisms
  Examples of single microbial cell

           Purple bacteria                Cyanobacteria




          First phototroph on earth   First oxygen evloving phototroph
Microorganisms Can Appear in Masses:
Bloom of Purple Bacteria
Microorganisms in Culture
History: The First Description of Microorganisms




     • Robert Hooke observed fruiting structures
       of molds in 1665 and was the first to
       describe microorganisms (Figure 1.8).
Adjustment


Lens
History: The First Description of Bacteria


• Antoni van Leeuwenhoek was the first to
  describe bacteria in 1676 (Figure 1.9).

  – The field of microbiology was unable to develop until
    Leeuwenhoek constructed microscopes that allowed
    scientists to see organisms too small to be seen with
    the naked eye.
Van Leeuwenhoek’s Microscope
Van Leeuwenhoek’s
drawing on various
organsisms
Blood Smear Viewed through van
Leeuwenhoek’s Microscope


    Erythrocytes      Leukocyte
History:The Concept of Biogenesis
Replaces Spontaneous Generation Theory


  • Spontaneous generation claims that life can
    originate from non-living matter.
  • Biogenesis states that living cells originate from
    living cells.
  • Louis Pasteur's disproved spontaneous
    generation.
  • His work led to the development of methods for
    controlling the growth of microorganisms.
Pasteur’s Swan Neck Experiment
History: Pasteur’s Conclusions

  • The bended neck allowed air to enter the bottle
    and the liquid but trapped any particulates
    including microorganisms.
  • No microbial growth as long as the liquid broth
    did not come in contact with the microbes.
  • Hence air alone was not sufficient to generate
    life.
History: Microorganisms Cause Disease

  • Robert Koch developed a set of postulates
    (Figure 1.12) to prove that a specific
    microorganism causes a specific disease.
     – B. anthracis causes anthrax
     – M. tuberculosis causes tuberculosis
Koch’s Postulates

  • The suspected pathogenic organism should be
    present in all cases of the disease and absent from
    healthy animals.
  • The suspected organism should be grown in pure
    culture—that is, a culture containing a single kind of
    microorganism.

  • Cells from a pure culture of the suspected organism
    should cause disease in a healthy animal.

  • The organism should be reisolated and shown to be
    the same as the original.
History: Microbial Diversity and
Geochemical Cycling

  • Beijerinck and Winogradsky
     – Late 19th century
     – Studied bacteria in soil and water
  • Beijerinck
     – Developed the enrichment culture technique for the
       isolation of representatives of various physiological
       groups
  • Winogradsky
     – Biogeochemical cycling
History: Host Defense against Microbes


• Ehrlich: Magic Bullet (antibodies)
• Metchnikoff: Phagocytosis
• Fleming: Lysozyme
History: Antimicrobial Drugs


                        Discovery of Penicillin



Sir Alexander Fleming
Modern Era of Microbiology

• Applied microbiology : agricultural, soil, marine
• Basic microbiology : microbial systems,
  biochemistry, genetics
• Molecular microbiology : biotechnology,
  genomics
• In the middle to latter part of the 20th century,
  basic and applied microbiology worked hand in
  hand to usher in the current era of molecular
  microbiology.
Landmarks in Microbiology
MICROSCOPY

 • Microscopes are essential for microbiological
   studies
 • Light microscopes: cellular resolution
    –   bright-field (stains)
    –   dark-field
    –   phase contrast
    –   fluorescence (stains)
 • Electron microscopes: subcellular resolution
Light Microscopy: Optics

 • Visualization depends on magnification (lenses)
   and resolution (physical properties of light)
 • The limit of resolution for a light microscope is
   about 0.2 m (or 200 nm)
    – Objects closer than 0.2 m cannot be resolved
 • Total magnification is product of the magnification
   of its ocular and its objective lenses
Microscopy: Stains

 • Staining (Figures 4.3, 4.4) is used to increase
   contrast in bright-field microscopy
    – Simple: one dye stains all cells
    – Differential: combination of dyes allows differential
      staining of different populations
Simple Stain
Differential Stain
Example for Gram Stain

        E. coli (g-)   S. aureus (g+)
Microscopy: Dark Field
  • Greater resolution
  • Light reaches
    specimens only from
    the side
  • Only the specimen itself
    is illuminated                Candida sp.




                               Treponema pallidum
Microscopy: Phase Contrast

 • May be used to
   visualize live samples
   and avoid distortion
   from cell stain
 • Image contrast is
   derived from the
   differential refractive
   index of cell structures.
Microscopy: Fluorescence

• Visualization of autofluorescent
  cell structures (e.g., chlorophyll)
  or fluorescent stains
• Can greatly increase the
  resolution of cells and cell
  structures
• Many functional probes
  available
Example for Differential Fluorescence Stain




         Psuedomonas (green) Bacillus (orange)
Microscopy: Electron Microscopy

 • Electron microscopes have far greater resolving
   power than light microscopes, with limits of
   resolution of about 0.2 nm
 • Two major types of electron microscopes
    – Transmission electron microscopy (TEM) for observing
      internal cell structure down to the molecular level
    – Scanning electron microscopy (SEM) for 3-D imaging
      and examining surfaces
Electron Microscopy

        TEM              SEM




      Pseudomonas     Mycobacterium
Additional Resources

  • http:// www.millennium-
    ark.net/News_Files/Newsletters/News010106_30f5NCB/A
    nthrax.hand.gif
  • http://pathmicro.med.sc.edu/ghaffar/anthrax4.gif
  • http://microota.nutr.med.tokushima-
    u.ac.jp/foodmicro/image/
  • http://pathmicro.med.sc.edu/mycology/candid.jpg
  • www.johnes.org/.../EM_scanning-lg.jpg
  • www-medlib.med.utah.edu
  • Tortora et al, 9th edition