Bacteriology BIO 309 Summer 2003

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Bacteriology

BIO 309

Summer 2003

Dr. H. DeHart

215 TCNW

745
-
5136

Heather.DeHart@wku.edu

Introduction to Microbiology
-

Chapter 1


Microbiology:





The study of microorganisms (large,
diverse group of cells living individually or
as clusters, includes the viruses, which are
microscopic but not cellular)

Basic vs. Applied Microbiology


Basic Microbiology
: Properties that
all

cells
have in common, short life cycles, biochemical
and genetic studies.


Applied Microbiology
: Practical problems in
medicine (diseases vs. microbes living in
assoc. with the body without causing harm),
agriculture (soil fertility, etc.), and industry
(production of antibiotics, food products, etc.).

Importance of Microorganisms


Precursors for higher organisms


Sustain higher organisms and the
environment by:


Production of oxygen


Recycling of key nutrients


Degradation of organic matter

The Cell

(What all cells have in common)


Fundamental unit of life


Has a
cell membrane

to separate the
contents of the cell from the outside world


Has a
nucleus

or
nucleoid

that contains the
genetic material (DNA) for
reproduction


Contains
cytoplasm
, where the machinery
for cell growth and function are present

The Cell (continued)


Is made up of 4 chemical components:


proteins


nucleic acids


lipids


polysaccharides


Regulates what comes and goes; is an open
system

The Cell (continued)


Carries out metabolism (takes up chemicals
from the environment, transforms them into
energy usable by the cell, and eliminates
waste products)


Communicates (responds to chemical
signals in the environment)


Is capable of
differentiation
,
movement
,
and
evolution


Refer to Fig. 1.3 in the text

How and Where do Microbes Live?


Cells live in nature associated with other cells in
groups called
populations
.


The location in an environment where a microbial
population lives is called the
habitat
.


In nature, populations of cells usually live and interact
with other populations of cells in groups called
microbial communities
.


Living organisms together with the physical and
chemical constituents of their environment = an
ecosystem
.

The Extent of Microbial Life


Prokaryotes (bacteria) constitute the major
portion of biomass on Earth and are key
reservoirs of essential nutrients for life.


Most prokaryotes live underground in
oceanic and terrestrial subsurfaces instead
of on the surface of the Earth.

Harmful Microorganisms


Microbes cause infectious diseases such as
influenza, pneumonia, tuberculosis,
gastroenteritis, infant diseases, and
diphtheria.


For developed countries, these diseases were
a much bigger problem in the past than they
are today. Why is this? Also, why are they
still a major problem for developing
countries? Refer to Fig. 1.7 in the text.

Harmful Microorganisms
(continued)


What populations of people are currently
most susceptible to or affected by microbial
diseases in developed countries? Why?


It is important to prevent spoilage of foods
by microbes by methods such as canning,
freezing, drying, pickling, and salting.


Refer to Fig. 1.7 in the text

Beneficial Microorganisms


Agriculture
:


Legumes

form
nodules

on their roots, in
which microbes convert N
2

to fixed N
compounds that the plant can use.
Microbes also cycle other key nutrients.


Farm animals (cattle, sheep) have a
digestive organ called a
rumen

in which
microbes digest grass and hay into usable
compounds for the animal.

Beneficial Microorganisms
(continued)


Food industry
: Products manufactured via
microbial activity: cheese, yogurt,
buttermilk, sauerkraut, pickles, some
sausages, baked goods (ex. breads),
alcoholic beverages, soy sauce.


Energy Production
: Microbes convert
domestic and animal waste and surplus
grain to biofuels such as methane (natural
gas) and ethanol (= “green power”).

Beneficial Microorganisms
(continued)


Environment
: Microbes can clean up
pollution through a process called
bioremediation (their metabolism converts
toxic compounds to innocuous compounds).


Biotechnology
: Genetically modified
microbes are specially designed to
synthesize certain products of high
commercial value, ex. human insulin.


Refer to Fig. 1.6 in the text

The History of Microbiology


1664
-

Robert Hooke

described the fruiting
structures of molds.


1684
-

Antoni van Leeuwenhoek

built the
first microscope and was the first person to see
microorganisms, he called them “wee
animalcules.”


1850
-

Ferdinand Cohn

founded bacteriology
(the study of bacteria), discovered the genus
Bacillus

and endospores.

The History of Microbiology
(continued)


1884
-

Robert Koch

discovered the
mechanism of transfer of infectious disease
between individuals, known as
Koch’s
Postulates (Germ Theory of Disease)
.
Refer to Fig. 1.12 in the text.


1885
-

Louis Pasteur

dispelled the myth of
Spontaneous Generation
. Refer to Fig.
1.11 in the text. What did Pasteur’s
discoveries lead to?

Koch’s Postulates

Pure Cultures


Developed by Robert Koch.


Premise: To link a specific microbe to a specific
process (ex. disease), the organism must first be
isolated in pure culture.


Koch first developed nutrient sources on which to
grow bacteria, ex. potato slices, gelatin. Why is it
important to be able to grow bacteria on solid
medium?


Bacterial colonies can arise from a single bacterial
cell and have characteristic shape and color. Refer
to the quote by Koch on p. 15 of the text.

Agar


1884
-

Walter Hesse first used agar is a
solidifying agent.


Agar is composed of a polysaccharide
derived from red algae.


Agar liquifies at 55
°
C as opposed to gelatin,
which is liquid at 37
°
C (=98.6
°
F or body
temp.), the optimum temp. at which most
human pathogens (disease
-
causing
microbes) grow. Why is this important?

Petri Dish


1887
-

Richard Petri modified Koch’s flat plate
technique and designed the Petri dish.


Advantages:


stackable


can be sterilized separately from the medium (ex.
nutrient agar)


cover prevents contamination


colonies formed on the surface are fully exposed to air
and easily manipulated


currently made of glass sterilized by dry heat or
plastic sterilized by a gas sterilant.

Metabolically Significant Actions
of Microorganisms


1889
-

Sergei Winogradsky proposed the
concept of
chemolithotrophy
, the oxidation
of
inorganic

compounds coupled to the
release of energy.


Winogradsky also concluded that these
organisms were
autotrophs

(“self
-
feeding”); obtained their carbon from CO
2

in the air.

Enrichment (or Selective)Culture


1901
-

Martinus Beijerinck proposed selecting
specific microbes from a natural sample
through the use of specific culture media and
incubation conditions that favored growth of
only one type or a physiologically related
group of organisms.


Beijerinck also described the first virus
(TMV): small (escaped filtration), no bacterial
but became incorporated into plant cells,
requiring them to reproduce.

Development of Subdisciplines of
Microbiology
-

Applied


Medical Microbiology

-

study of bacterial
pathogens


Immunology

-

determination of the
mechanisms by which pathogens infect the
body and are resistant to the body’s defenses.


Agricultural Microbiology

-

microbial
processes in the soil that are beneficial or
harmful to plant growth.

Development of Subdisciplines of
Microbiology
-

Applied (continued)


Industrial Microbiology

-

important uses of
microbes, ex. synthesis of antibiotics and
commodity chemicals.


Aquatic Microbiology

-

microbial processes in
bodies of water (lakes, rivers, oceans, etc.).
One branch deals with processes for treating
sewage and providing safe drinking water.


Microbial Ecology

-

biodiversity and activities
of microbes in their natural environments.

Development of Subdisciplines of
Microbiology
-

Basic


Microbial Systematics

-

discovery and
classification of new microorganisms.


Microbial Physiology

-

study of the
nutrients that microbes require and the
products they make.


Cytology

-

study of the physical and
chemical structure of microbes.

Development of Subdisciplines of
Microbiology
-

Basic (continued)


Microbial Biochemistry

-

study of the
complement of microbial enzymes and the
chemical reactions they carry out.


Virology

-

the study of viruses. Viruses that
infect bacteria are called bacteriophages.


Biotechnology
-

introduction of foreign
DNA into bacteria and control of its
replication and characteristics.