Lecture 1 Introduction, History and Microscopy - Cal State LA ...

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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.


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: The importance of Microbiology

Introduction: Examples for Microorganisms

Purple bacteria

Cyanobacteria

Examples of single microbial cell

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
).


Lens

Adjustment

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




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.

Koch’s Postulates

History: Microbial Diversity and
Geochemical Cycling


Beijerinck and Winogradsky


Late 19
th

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

Sir Alexander Fleming

Discovery of Penicillin

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 20
th

century,
basic and applied microbiology worked hand in
hand to usher in the current era of
molecular
microbiology
.


Landmarks in Microbiology

M
ICROSCOPY


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

S. aureus
(g+)

E. coli
(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

Pseudomonas

Mycobacterium


TEM SEM

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, 9
th

edition