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
Bacteria consist
of only a single
cell, but don't let
their small size
and seeming
simplicity fool
you. They're an
amazingly complex
and fascinating
group of
creatures.
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Builders of Modern Life
Bacteria are among
the earliest forms
of life that appeared
on Earth billions of
years ago.
 Bacteria helped
shape and change
the young planet's
environment,
eventually creating
atmospheric oxygen
that enabled other,
more complex life
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forms to develop.

What are bacteria?

Bacteria are unicellular, living things.

Prokaryotic cells (without a nucleus).

Obtain nutrients is different ways:
 Photosynthetic autotrophs- convert inorganic
molecules into sugar using sunlight
 Heterotrophs- consume food by growing on it
 Saprophytes- obtain food by decomposing dead
material
 Chemotrophs- manufacture organic compounds
from inorganic compounds such as hydrogen
sulfides
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Bacteria feeding on saguaro
Cyanobacteria in
a lake
Chemotrophs at
hydrothermal Vent
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Bacteria used in
wastewater treatment
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Classification of Prokaryotes
 All
prokaryotes belong to the
kingdoms:
Archaea
Eubacteria
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Archaea





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First discovered in 1970’s
Discovery made the term “Moneran” obsolete
Biochemically different from eubacteria
May have evolved in the harsh conditions of
early Earth
They are abundant in, but not restricted to,
extreme environments because of their ability to
withstand the harshest of environments
May be the early ancestors of eubacteria
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Characteristics of Archaea

Archaea (Formerly Archaebacteria)
 Lack
an important carbohydrate (peptidoglycan)
found in the cell wall of nearly all Eubacteria.
 Live in harsh environments
 Oxygen-free
environments
 Methanogens
(ex. Thick mud & digestive tracts)
 Produce methane gas
 Salty
environments
 Extreme
Halophiles
 Great Salt Lake/Dead Sea
 Hot
Springs
 Thermoacidophiles
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Characteristics of Eubacteria
 Eubacteria
= Modern Bacteria
 Unicellular
 Cell
walls contain peptidoglycan
 Genes lack introns
 Reproduce asexually by binary fission
 Either autotrophic or heterotrophic
 Extremely diversified groups
 Certain types may be ancestors of
mitochondria
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Identifying Prokaryotes
 Bacterial
Shapes

Bacillus
= Rod
Coccus = Round
Sprillium = Spiral
Colony growth
 Cells
arranged in
particular ways
Form long chains
 Grow in clusters


Bacterial
movement
 Flagella
 Some
do not move
 Some glide
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Shape #1 is rod shape, also known
as bacillus.
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Shape #2 is sphere shaped, also
known as coccus.
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 Shape
#3 is
spiral shape,
also known as
sprillum
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Micrococcus luteus tetrad
Vibrio
Bacillus cereus
Rhodospirillum
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Bacterial Structures


Cell Wall- support and protection
No nucleus- Bacterial DNA is usually coil-shaped
and not enclosed in a nuclear membrane.
 Most
bacteria also have small ring-shaped pieces of
DNA called plasmids



Capsule- protective layer that surrounds the cell
Some have flagellum to aide with movement
Pilus aides in adhesion to other cells
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Bacterial growth and reproduction
Grow and reproduce at an incredible rate
when conditions are favorable
 Bacterial growth stays under control due to
limiting factors such as nutrient availability
and production of waste products.
 Reproduction methods

 Binary
fission
 Conjugation
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Binary fission
Asexual
reproduction
 When a bacterium
is almost double in
size, it replicates
it’s DNA and
divides in half.

 Example:
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E. coli
Conjugation

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Sexual reproduction
Long bridge of protein in
between 2 bacterial cells
connecting them.
Genetic material from
donor cell is transferred
to the other cell.
Recipient cell ends up
with different combo of
genes.

Leads to genetic
variation, evolution,
antibiotic resistance
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Example
Spore formation
Spores form when conditions become
unfavorable.
 Endospore is a type of spore that forms a
thick internal wall that protects the DNA
and cytoplasm.
 Endospores can remain dormant for
months to years while waiting for favorable
conditions to arise.

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Food production
 Yogurt,

cheese, buttermilk, sour cream, pickles
Used in industry
 Digest
petroleum; clean up oil spills
 Used in mining
 Used in sewage treatment plants

Symbiosis
 Digestion
 Nitrogen-fixation
and plants
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
Pathogens
 Disease
causing agents
 Small number of bacteria are pathogens

Examples of pathogenic bacterial
infections:
 Syphilis,
cholera, tuberculosis, bubonic plague,
botulism, tetanus, gingivitis, strep throat

Pathogens cause disease by:
 Damaging
cells and tissues for use of nutrients
 Release toxins
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
Antibiotics destroy
bacteria by disrupting
the structure of the
cell wall
Over prescribing of
antibiotics is causing
antibiotic resistance
because bacteria
mutate readily
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Bacterial respiration

Energy is supplied by respiration and
fermentation
 Respiration
involves oxygen and breaks down food
molecules to release energy
 Fermentation is energy production without oxygen

Obligate aerobes
 Bacteria

that require a constant supply of oxygen
Obligate anaerobes
 Must live in the absence of oxygen
 Example: Clostridium botulinum
 If subjected to air and allowed to grow on food, it will produce
toxins that cause severe food poisoning.

Facultative anaerobes
 Can survive with or without oxygen
 Allow facultative anaerobes to live almost
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anywhere.
The End
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