Bacteria
Ch.19-1
By: A. Cortez
Classifying Prokaryotes
Thanks
to Robert Hooke and
Anton van Leeuwenhoek, the
invention of the microscope
opened our eyes to the hidden,
living world around us.
Microscopic life covers nearly
every square centimeter of Earth
Classifying Prokaryotes
Remember!!!!- The smallest and most
common microorganisms are
Prokaryotes
They are single-celled, lack a nucleus
For many years prokaryotes were called
“bacteria”
Classifying Prokaryotes
Until most recent
prokaryotes were
placed in the
kingdom-Monera.
Now, they are
divided into two
kingdoms:
Eubacteria and
Archaebacteria
Classifying Prokaryotes
Remember they are
much smaller then
eukaryotic cells.
Prokaryotes range
about 1 to 5
micrometers
Eukaryotes range:
10-100 micrometers
in diameter.
Classifying Prokaryotes
Eubacteria
Eubacteria is the larger of the two
kingdoms
Has a wide range of organisms with different
lifestyles.
They live mostly everywhere: freshwater,
land, salt water, and within the human body.
They have a cell wall that protects from
injury and the cell wall contains a
peptidoglycan which is a source of
carbohydrate.
Classifying Prokaryotes
Archaebacteria
Archaebacteria look very similar to
eubacteria under microscope.
They are both small, lack nucleus, have
cell wall, but chemically archaebacteria are
quite different.
Classifying Prokaryotes
Archaebacteria
They lack peptidoglycan with
eubacteria does have.
Also, The DNA sequences of key
archaebacterial genes are more like those
of eukaryotes.
They live in extreme environments
such as: volcanos, areas of boiling point
waters, the great salt lake in Utah.
Identifying Prokaryotes
Prokaryotes are
identified by
characeristics
such as shape, the
chemical nature
of their cell walls,
the way they
move, and the
way they obtain
energy.
Identifying Prokaryotes
Shapes
A Rod-shaped
prokaryote is
called a Bacilli
A Spherical
prokaryote is
called a Cocci
Spiral and
corkscrew-shape is
called a Spirilla
Cocci
Spirilla
Identifying Prokaryotes
Identifying Prokaryotes
Cell Walls
Two types of cell
walls
Scientist use a
method called
Gram staining to
tell them apart.
The gram stain
consist of two
dyes: violet and
red.
Identifying Prokaryotes
Cell Wall
The violet stain is applied first , which
stains peptidoglycan cell wall.
Then followed by a alcohol treatment
that tends to wash out the stain.
Gram Positive bacteria has thick
peptidoglycan walls that remain dark in
color.
Gram Negative bacteria has a thinner
walls, alcohol dissolves peptidoglycan,
light color:pink, light red.
Identifying Prokaryotes
Movement
You can identify
prokaryotes by
where they move
and how they
move.
They are propelled
by flagella, a
whiplike structure
used for movement
Identifying Prokaryotes
Movement
Other
prokaryotes lash,
snake, or spiral forward.
Also some Prokaryotes
glide slowly along a layer of
slimelike material they
secrete
Metabolic Diversity
Most prokaryotes are heterotrophs,
meaning that they obtain energy by
consuming organic molecules made by
other organisms.
Other prokaryotes are autotrophs and
make their own food from inorganic
molecules.
Two types of Heterotrophs
1. Chemoheterotrophs
2. Photoheterotrophs
Metabolic Diversity
Most
heterotrophic prokaryotes must
take in organic molecules for both
energy and a supply of carbon, these
prokaryotes are called
chemoheterotrophs.
We are chemoheterotrophs
ourselves
Which means prokaryotes compete
directly with us for food.
Metabolic Diversity
A
smaller group of
heterotrophs called
photoheterotrophs , use
sunlight for energy, but also
need organic compounds as a
carbon source.
Metabolic Diversity
There
are two types of autotrophs.
1. Photoautotrophs
2. Chemoautotrophs
Photoautotrophs-use light energy
to convert carbon dioxide and
water to carbon compounds and
oxygen.
Metabolic Diversity
Chemoautotrophs- make organic
carbon molecules from carbon dioxide
They do not require light as a source of
energy.
Instead they consume chemical
reactions from ammonia, hydrogen
sulfide, nitrites, sulfur, or iron.
Examples: ocean floor plants
Metabolic Diversity
Releasing Energy
Bacteria need a constant supply of energy.
Organisms that require a constant
supply of oxygen in order to live are
called: Obligate Aerobes.
Organisms(bacteria) that do not require
oxygen and, in fact may be killed by it are
called: Obligate Anaerobes.
Organisms that can live with or without
oxygen are called Facultative
Anaerobes
Growth and Reproduction
Conjugation:
Bacteria are able
to exchange
genetic
information
A hollow bridge
forms between
two bacterial
cells
Growth and Reproduction
Binary Fission:
When a bacterium
has grown so that
it has nearly
doubled in size, it
replicates its
DNA and divides
in half, producing
two identical
“daughter” cells.
Growth and Reproduction
Spore formation:
when growth
conditions become
unfavorable, many
bacteria form
structures called
spores.
One type of spore is
called endospore
A thick internal wall
that encloses its
DNA and a portion of
its cytoplasm.
Importance of Bacteria
Bacteria
are vital to maintaining the
living world.
Some are producers that capture
energy by photosynthesis.
Others are decomposers, which
break down the nutrients in dead
matter and the atmosphere.
Importance of Bacteria
Decomposers
Bacteria help the
ecosystem recycle
nutrients. Maintaining
equilibrium
Ex. When a tree dies,
bacteria attacks and
digests the dead tissue.
Breaking it down
into simpler tissue,
which are released
into the soil.
Importance of Bacteria
Quick reminder !!!!!
That Nitrogen (N), gas makes up
approximately 80 percent of Earth’s
atmosphere.
Plants need nitrogen to make amino
acids, the building blocks of proteins.
However, plants cannot use nitrogen gas
directly……………
Importance of Bacteria
Nitrogen must be changed chemically to
ammonia (NH3) or other nitrogen
compounds.
This process of converting nitrogen gas
into a form plants can use is known as
Nitrogen Fixation.
Human Uses of Bacteria
Bacteria provides us with products we
depend on every day.
1. Production of a wide variety of foods
and beverages.
2. Digest petroleum to clean oil spills
3. Removal of poison from water.
4. Humans benefit from E.coli , by it
making a number of vitamans that body
cannot itself.
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