Download 5. Prokaryotes 11B

PROKARYOTES: 2 kingdoms
Classification
In the 3 Domain system: 2 contain prokaryotes
1. Domain Archaea: Extreme bacteria
2. Domain Bacteria: Everyday bacteria
(The third domain is called Eukarya and it includes
eukaryotic organisms, including humans!)
In the 6 Kingdom system: 2 contain prokaryotes
1. Kingdom Archaebacteria: Extreme bacteria
2. Kingdom Eubacteria: Everyday bacteria
(Other kingdoms: Protista, Fungi, Plantae, Animalia)
Example of everyday bacteria:
Cyanobacteria
 Previously called blue-green
algae
 Common in water
ecosystems
 Use photosynthesis to
generate oxygen
 Chloroplasts may have
evolved from cyanobacteria
Examples of Extreme Bacteria
Extreme halophiles: Live in high saline environments
Seawater evaporating
ponds at the edge of
San Francisco Bay –
used for commercial
salt production
Examples of Extreme Bacteria
 Methanogens = Live in
swamps and marshes,
where other creatures
have used all of the
O2
 Also found in guts of
cattle, at garbage
dumps and sewage
treatment facilities
 Produce methane as
a waste product
Examples of Extreme Bacteria


Extreme thermophiles: Thrive in very hot environments
Orange and yellow colonies of thermophiles in the
hot water of a Nevada geyser
Common Characteristics
 Bacteria
are the
simplest living creatures
 No nucleus
 A loop of DNA (not
chromosomes)
 No membrane-bound
organelles
 Most are unicellular
 Most have a cell wall
 Are 5 microns in size
Now: Draw this bacterium!
Figure 6.6 A, B
Now create a chart in your notes to compare the
characteristics of Bacteria and Archaea. Your column
headings should be:
 Morphology
 Metabolism
 Nutrition
 Habitat
 Genetics
 Reproduction
Morphology
Some bacteria have…
 Capsule – useful for protection,
especially from the human
immune system
 Pili - sticky appendages
 Flagellum - for motion
Classification: Shape
A microscope-based method of classifying bacteria
1 m
(a) Spherical (cocci)
2 m
(b) Rod-shaped
(bacilli)
(c) Spiral
5 m
Metabolism
RESPIRATION: when sugar is broken down to make cellular
energy (called ATP)
 some bacteria perform aerobic respiration (using O2),
some perform anaerobic respiration (no O2)
 Obligate aerobes: must have oxygen (E.g. humans!)
 Obligate anaerobes: live without oxygen (E.g. tetanus
bacteria)
 Facultative anaerobes: use oxygen if present
Nutrition
Heterotrophic = eat others
Autotrophic = make own food
Photoautotroph = energy from
light
Chemoautotroph = energy from
chemical reactions, (H2S)
many are found near deep
ocean vents
Genetics
 Simple ring of
DNA
 Many bacteria
have plasmids =
extra loops of
DNA that often
give bacteria
additional
beneficial genes
such as antibiotic
resistance
Chromosome
Asexual Reproduction – Binary Fission
Origin of
replication
1 DNA copying begins.
2 One copy of the DNA is now at
each end of the cell.
3 The plasma membrane pinches
inward, and a new cell wall is
deposited.
4 Two daughter cells result.
Cell wall
E. coli cell
Two copies
of origin
Origin
Plasma
Membrane
Bacterial
Chromosome
Origin
Sexual reproduction - Conjugation
 The direct transfer
of DNA between 2
bacteria, via a
cytoplasmic
bridge (made
when 2 pili
connect)
Hmmm…Why is this
considered
‘sexual’?
Sex pilus
1 m
Crucial roles in ecosystem
 If prokaryotes were to disappear the prospects for any
other life surviving would be dim
e.g. Nutrient cycling
 Function as decomposers, act to recycle chemical
elements between the living and nonliving components of
the environment (Breaking down corpses, dead
vegetation, and waste products)
 Nitrogen-fixing prokaryotes
Symbiotic Relationships
1. Mutualism = both organisms benefit
e.g. bacteria in human digestive tract
e.g. bioluminescent bacteria on eye of flashlight fish
2.
Commensalism = one organism benefits and
the other is neither harmed nor helped (rare in
nature!)
3. Parasitism = one organism is harmed while the
other benefits (usually multi-cellular and nonlethal)
Pathogen = similar to parasites, but more often
unicellular and lethal
Pathogenic Prokaryotes
 Prokaryotes
cause about
half of all human
diseases (e.g.
Lyme disease)
Figure 27.16
5 µm
Endotoxins
Exotoxins
 When gram negative
bacteria die, their
membrane breaks down
and is toxic
 A poison produced by the
bacteria
E.g. Salmonella bacteria that
cause food poisoning
E.g. Cholera bacteria
produce toxins that cause
chloride ion release which
causes dehydration and
severe diarrhea
Now: Use your textbook or
computer to add in the
characteristics of Archaea
Watch a movie about the rise of infectious disease!