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.
