Microbiology

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Biol 3400



Tortora et al
-

Chap. 1


1

An Overview of Microbiology


Microbiology
-

The study of microscopic life
-

microorganisms



Why study microorganisms?





What are microorganisms?








I
.

What is a cell?


Cells are highly organized structures


An organism’s
basic unit of structure
and function
.


Cell provides for the following essential ch
aracteristics of life



Order



Reproduction



Heredity



Evolutionary adaptation



Growth and development



Metabolism



Response to environment



Homeostasis



All cells are separated from the external environment by a
plasma membrane


All cells contain
DNA

at some stage in their lifetime. They are storehouses of
information. Cells are also capable of interpr
eting this information


Where did the first cells com
e from?


All present day cells have apparently evolved from the same
ancestor
.



Biol 3400



Tortora et al
-

Chap. 1


2

II.

Cellular Organization


Unicellular
-

single cell


e.g.,

-

bacterium


Multicellular
-

cellular associations and differentiation but lack tissues (next level in the
hierachy

of biological organization)


e.g.,

-

filamentous blue green algae



-

mushrooms
-

fungal fruiting bodies



i) Variation in cell size



Smallest cell

-

mycoplasma (0.1 to 1.0 µm in diameter)



Typical bacterial cells

-

10 x larger (1 to 10 µm in diameter)



Eukaryotic cells

-

10 x larger than bacteria (10
-

100 µm)



Largest cell

-

Ostrich egg yolk
-

the size of a small orange (5
-

10 cm in diameter)


Notable Exceptions



Epulopiscium fishelsoni

-

Bacterial cell 60 X 800 µm



Thiomargarita namibiensis
-

Bacterial
cell up to 0.75 mm in diameter



Nanochlorum eukaryotum

-

eukaryotic algae
-

cells 1 to 2 µm in diameter



ii) Cell types


Prokaryotic cell

Eukaryotic cell

least complex

most complex


no membrane bound nucleus

membrane bound nucleus


no

membrane bound organelles

membrane bound organelles


Domains:

Domain

Bacteria and Archaea

Eukarya


generally smaller

generally larger




Biol 3400



Tortora et al
-

Chap. 1


3

iii)
Viruses



exception to the rule
-

acellular



composed predominantly of protein and
nucleic acid

-

lack cell or plasma membrane



Not a dynamic open system like a cell



They have no means of independent life support, rely on host's metabolic machinery



if infect host they are capable of directing viral reproduction



infect virtually all living cells



Smal
lest virus is 10 nm in diameter; Largest viruses ~ 300 nm in diameter




III

Diversity of Life & Evolutionary Relationships


> 1.8 million species have been identified.


Taxonomy

-

The branch of biology concerned with the naming (nomenclature) and
classifi
cation of organisms.


Systematics
-

The study of biodiversity in an evolutionary context


Taxonomic Hierarchies


Organizational levels taxon (
pl
.
-

taxa)


Ideally



Represent a coherent degree of homology i.e., genetic and evolutionary similarity



Members of each taxon should be monophyletic (i.e., same evolutionary history; members of a
genus had a common ancestor)


Taxa

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species


Scientific Names



Biol 3400



Tortora et al
-

Chap. 1


4

I
V.

Diversity of microorganisms



Prokaryotes &
Eukaryotes



Metabolism



Tolerance for extreme environments






V.

Ecology and Microorganisms



An important consideration is that
"
p
opulations of cells rarely live alone in nature"



They usually live in association with other populations
-

microbial
communities


Population

-

an assemblage of a single type of cells (single species).
May be c
lones of
an original parental cell.




Interactions occur within and between populations and also between the organisms
and their physical and chemical environments
(ecosystem)



VI
.

Laboratory Culture



We often grow microorganisms in the laboratory and in order to do this must p
rovide
the appropriate conditions for growth


Culture medium

(
plural =
media)
-

aqueous solution containing necessary nutrients



Semisolid medi
um


agar


Pure culture

-

a culture containing a single cell type


Sterilization





Microbes are ubiquitous



How can you produce a pure culture from a heterogeneous mixture?


Aseptic technique

-

used to prevent contamination during manipulation of cultures and
sterile

media



Sterilize all media and implements for handling materials of interest



Clean working area



Limit exposure to potential sources of contamination



Biol 3400



Tortora et al
-

Chap. 1


5

Preparation of Pure Cultures


Streak plate technique



Dilution


Deposition of individual cells or clumps of cells (known as colony forming
units or CFU) on agar medium



Cell growth


multiplication


resulting in the production of colonies (visible mass
of cells)



each isolated colony on

the streak plate is assumed to have originated from a
single CFU
(It is unknown whether the cells in the colony came from a single cell or
a clump of cells)



VII

History


i) First observations of microorganisms

Robert Hooke (1665)

Anton van Leeuwenhoek
-

1674
-

1723


Cell Theory


Matthias Schleiden (botanist; 1838) & Theodor Schwann (zoologist; 1839)

i) all living things consist of cells.

ii) all cells come from preexisting cells.



ii) Birth of Microbiology
-

Late 19
th

century


Ferdinand Cohn (1828
-
1898)



founder of bacteriology


mid 1800s



Discovered genus
Bacillus

and endospore formation



Simple methods for preventing contamination of sterile culture media


Louis Pasteur (1822
-
1895)

-

father of microbiology


mid to late 1800's


Important discoveries



An
aerobic life
-

life without oxygen



Industrial Microbiology



Ethanol fermentation



Pasteurization



Vaccines


rabies, anthrax



Disproved the theory of spontaneous generation






Biol 3400



Tortora et al
-

Chap. 1


6

Robert Koch (1843
-
1910)



Germ theory

of disease


Koch's Postulates

(Fig 14.3)



used to prove that a specific type of organism is the cause (etiological agent) of a
specific disease

(i.e.,
Bacillis anthracis

and anthrax)


1. The causative agent must be present in all "animals" with the disease and absent
from healthy "animals".

2. T
he agent of disease can be isolated from the diseased "animal" and can be
cultivated in pure culture in the laboratory

3. The disease can be reproduced by inoculating a portion of the laboratory culture into
healthy "animals".

4. The agent of disease can

be re
-
isolated from the infected "animal" and again
cultivated in the laboratory.




Pure culture technique



iii)
Vaccination


Edward Jenner



Used cowpox virus to vaccinate against smallpox virus



Vaccines now produced against many infectious agents


vaccin
es may be live
attenuated or avirulent strains of microorganisms, killed microorganisms or specific
components of the etiologic agents



iv) Chemotherapeutic Agents



Antimicrobial compounds may be synthetic or isolated from natural sources
(
antibiotics)


Antibiotics

-

substances produced by microorganisms that kill (bacteriocidal) or prevent
the growth (bacteriostatic) of other microorganisms.


Alexander Fleming (Scottish bacteriologist) discovered antibiotics
in 1928
with the
discovery of penicillin produ
ced by a fungus called
Penicillium
chrysogenum


Selman Waksman
-

early 1940's discovered streptomycin
-

Streptomyces griseus








Biol 3400



Tortora et al
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Chap. 1


7

iv

Microbial Ecology

Early 1900's


Martinus Beijerinck (1851


1931)



nitrogen fixation



sulfur cycling



enrichment technique

-

use of specific culture media and incubation conditions that
favour growth of one type of microorganism while constraining the growth of others.


Sergei Winogradsky (1856
-
1953)



nitrifying bacteria (NH
4
+



NO
2
-
)



chemoautotrophs



The role of microbes in
biogeochemical processes




v) Microbial Genetics and Molecular Biology


One Gene
-

One Enzyme Hypothesis

Beadle and Tatum (1941)
Neurospora


DNA
-

Hereditary Molecule

Bacterial transformation



Griffith (1928)
Streptococcus pneumoniae

-

transforming principle



Avery, McCarty, and MacLeod (1944) identified DNA as transforming principle


Transduction



Alfred Hershey and Martha Chase (1952)
-

Labelled T2 phage protein or DNA



DNA Structure



Watson and Crick (1953)



Biotechnology & Recombi
nant DNA Technology



Late 1970's until present





Biol 3400



Tortora et al
-

Chap. 1


8

VII

What is the impact of microorganisms on humans?


1) Environment



A number of microorganisms are essential for the cycling of nutrients



We use these microbial processes to treat sewage and remove toxic
compounds
from the environment (bioremediation)


2
)
Disease Agents



Our bodies
are colonized by many different microbial species

-

normal microbiota



Diseases are caused by
pathogens

and diseases caused by microorganisms are
called
infectious diseases



Emerging infectious diseases

-



3
)
Agriculture



Microorganisms affect agricultural productivity in a number of ways

o

cause

diseases of crop plants and livestock

o

may also be beneficial to crop plants and animals

o

Biotechnological applications


4
)
Food Industr
y



Microorganisms cause spoilage of food



Microorganims are also used in the production of a number of food and beverages



5)
Biotechnology



"The industrial use of living organisms or their components to improve human health
and food production" (Campbell et al., 1999)



"Those processes in which living organisms are manipulated, particularly at the
molecular genetic level, to form useful produc
ts" (Prescott et al., 1999)




Biotechnology/
Molec
ular genetics has been used to
produce genetically modified
organisms (GMO)

for the following applications

o

Transgenic crop plants and livestock

o

Production of i
ndustrial
chemicals and
enzymes

o

P
roduction of p
harmace
utical compounds (i.e., insulin)


o

Medical t
reatments (gene therapy)