Transcript Lecture 1 Introduction, History and Microscopy

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
First phototroph on earth
Cyanobacteria
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
Pseudomonas
SEM
Mycobacterium
Additional Resources
• http:// www.millenniumark.net/News_Files/Newsletters/News010106_30f5NCB/A
nthrax.hand.gif
• http://pathmicro.med.sc.edu/ghaffar/anthrax4.gif
• http://microota.nutr.med.tokushimau.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