Name _______________________________
Per_______
Chapter 18 –Prokaryotes NOTES
Biology by Nowicki
All organisms in domains Archaea and Bacteria are considered prokaryotic.
What does it mean to be prokaryotic?
 Do NOT have a nucleus
 Do NOT have membrane bound organelles (like mitochondria, ER, Golgi)
 But they DO have ribosomes, DNA, cell membrane, cytoplasm/cytoskeleton
18. 4: Bacteria and Archaea
Prokaryotes are widespread on Earth
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prokaryotes are the most widespread and abundant
organisms on Earth
o a gram of soil may contain 10,000 types of
bacteria (prokaryotes) and 5 billion bacterial cells
- prokaryotes are microscopic
- prokaryotes are one of the earliest life forms
- prokaryotes are found inside your body, inside volcanoes, on your pencil- EVERYWHERE!
(ubiquitous)
- prokaryotes can be grouped based on their need for oxygen
o aerobic- need oxygen
o anaerobic- do not need oxygen
There are two domains/kingdoms that contain prokaryotes: Bacteria and Archaea
The domain Bacteria and Archaea are structurally similar but have different molecular
characteristics
- domain Bacteria is more diverse and widespread than domain Archaea
- domain Archaea is more likely to be found in harsh environments than domain Bacteria
Domain: Archaea
Domain: Bacteria
Kingdom: Archaea (formerly Archaebacteria)
Kingdom: Bacteria (formerly Eubacteria)
- “ancient”
- most diverse
- most heterotrophs (some autotrophs)
- most are heterotrophs (some autotrophs)
- cells walls WITHOUT peptidoglycan
- cell walls WITH peptidoglycan
- found in harsh/extreme environments
- found everywhere
Examples:
Examples:
o methanogens- don’t need oxygen
o Escherichia coli
(anaerobic), make methane gas
o Clostridium botulinum
o thermophiles- very hot water
o Bacillus anthracis
o
halophiles- very salty conditions, 10x
saltier than ocean water
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STRUCTURAL COMPARISONS OF BACTERIA & ARCHAEA
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both are small, single-celled organisms
both have
o cell walls
o plasma/cell membranes
o DNA (chromosome) in a circle in the cytoplasm (not found in a nucleus because they
don’t have a nucleus)
o ribosomes
both may have plasmids
o plasmid – small piece of genetic material (DNA) that can replicate separately from
the prokaryote’s main chromosome
both are generally motile – able to move on their own
o flagellum – whiplike structure outside of a cell used for movement
 attached to plasma membrane and cell wall
both often contain pili
o pili – thin, short, numerous projections that help prokaryotes stick (attach) to
surfaces and each other; pili also function in exchange of DNA/genes in bacteria
bacteria do NOT have cilia!
both have multiple shapes
o Archaea come in many shapes
o Bacteria have 3 basic shapes:
 bacilli(us) – rod-shaped
 spirilla(um) or spirochete – spiral-shaped
 cocci(us) – spherical (round)
Label:
coccus
bacillus
spirillum
o Bacteria have 2 basic arrangements
- strepto– strips or chains
- staphylo- clusters
If your doctor said you had strep throat (“Streptococcus”), what would shape and arrangement
of the bacteria look like under the microscope?
Answer:
Draw:
Chain of circles
(see above)
If your doctor said you had a staph infection (“Staphylococcus”), what would shape and
arrangement of the bacteria look like under the microscope?
Answer
Draw:
Cluster of circles
(see above)
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Bacteria Structure & Function
STRUCTURE
FUNCTION
Cell Wall
protects the cell and gives shape
Plasma (cell)
Membrane
regulates movement of materials into and out of the cell;
Cytoplasm
contains DNA, ribosomes, and organic compounds required to carry out life processes
Flagellum(a)
moves the cell
Ribosomes
site where proteins are made
DNA (chromosome) carries genetic information inherited from past generations
Plasmid
additional ring of DNA that contains genes for specialized functions, such as antibiotic
resistance, or structures, such as pili; used for genetic engineering
Endospore
protects the cell against harsh environmental conditions, such as heat or drought
(not shown in diagram)
Pilus (Pili)
assist the cell in attaching to other surfaces, which is important for reproducing
Capsule
layer of polysaccharide and protein that protects the cell from white blood cells; often
toxic to host organisms; makes it difficult to treat infections with antibiotics
Fill in the terms above on the diagram below. Then, number these structures starting with
the outside of the cell and moving to the inside: cell wall, capsule, plasma membrane
plasmid
DNA/chromosome
ribosome
flagella
Capsule - 1
cell wall - 2
pili
plasma membrane - 3
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Bacteria have various strategies for survival
GENE EXCHANGE IN PROKARYOTES
binary fission – prokaryotic asexual reproduction
 dividing in half: identical offspring
o chromosome copies itself (similar to DNA replication)
o the cell grows to double its size
o plasma membrane grows inward and divides the cell
into two equal-sized cells, each with a complete copy
of the original cell’s genes
conjugation – exchange of genetic material through a hollow
bridge of pili connecting 2 or more
cells
SURVIVING HARSH CONDITIONS
endospore – specialized cell with a
thick, protective wall formed for survival during unfavorable conditions
o bacterium copies its chromosome
o produces a wall around the copy
o thick wall withstands drying out (desiccation), temperature change, and disinfectants
 can last for centuries
18.5: Beneficial Roles of Prokaryotes
Prokaryotes provide nutrients to humans and other animals
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prokaryotes are key in animal digestive systems in balanced communities
o mutualistic symbionts
 host benefits
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bacteria benefits
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make vitamins and other compounds
keep away harmful microbes by filling niches they might occupy (out-competing
them)
break down food while getting a place to live
place to live has stable pH and temperature
many foods humans eat are fermented by
o ferment – chemically break down
 cheese
 pickles
 yogurt
bacteria
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sauerkraut
soy sauce
vinegar
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Prokaryotes play important roles in ecosystems
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principle decomposers (along with fungi)
recyclers of carbon, nitrogen, hydrogen, and sulfur through ecosystems
photosynthesizers –
o cyanobacteria produce oxygen; were key to increasing the oxygen content of early
earth
nitrogen fixers – fix nitrogen; convert atmospheric nitrogen into ammonia and other
nitrogen compounds plants can use
o some nitrogen-fixing bacteria are free-living
o some are symbionts
 legumes – plants (peas, beans, alfalfa, and clover) with mutualistic
relationship with nitrogen-fixing bacteria living in nodules in the roots
 bacteria provide usable nitrogen to the plant in the form of ammonia
 plant provides food and shelter to the bacteria
bioremediaters – process that uses microbes and other living things to break down
pollutants
o some bacteria can digest oil, others can digest poison
o important role in recycling and composting
o biodegradable – able to be broken down by bacteria
 many plastics are NOT biodegradable.
18.6: Bacterial Diseases and Antibiotics
Some bacteria cause disease
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some bacteria cause disease in plants and animals by disrupting the host organism’s
homeostasis in 2 basic ways:
o invading tissues and attacking cells
o making poisons, or toxins, that can be carried by blood through the body
tuberculosis (TB) – bacteria invade host tissues and use them for nutrients
o Mycobacterium tuberculosis multiply in the lungs, killing white blood cells that
respond to the invasion
o host’s reaction is to release enzymes that cause swelling; results in lung damage
o a healthy immune system can usually defeat a potential TB infection
food poisoning –
o Staphylococcus aureus – normally live in nasal passages
 when transferred to food it results in serious illness
 toxin it produces is not destroyed by cooking
o Clostridium botulinum – causes botulism which can be deadly due to the toxin
produced by the bacteria
 usually caused by improper canning of foods contaminated with spores
 bulging or dented cans may signal the presence of the bacteria
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opportunistic infections – normally harmless bacteria can be destructive when introduced to
a part of the host that is not adapted to them
o example – Streptococcus normally present in our mouth and noses and the surface
of our skin, but can become pathogenic in a sore or cut
 also causes pneumonia
Antibiotics are used to fight bacterial disease
antibiotic – chemical that kills or slows the growth of bacteria, often by stopping bacteria from
making cell walls
o produced naturally by some species of bacteria and fungi
o used as medicine for humans and other animals because we/they lack cell walls
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antibiotics don’t work on viruses – they don’t have cell walls either
antibiotics don’t work on Archaea - they have a different type of cell wall (no peptidoglycan)
overuse of antibiotics can lead to 1) illness if the intestinal “flora” or microbes are wiped out
and 2) resistance
Gram stain – the Gram stain is a method of using stain to tell two groups of bacteria within
Kingdom Bacteria apart. This was an important technique developed which is helpful in not only
diagnosing bacterial infection, but also in determining the antibiotic that the doctor uses to treat
the infection.
o Gram negative bacteria stain red. These bacteria only have a thin layer of
peptidoglycan in the cell wall, but have an extra layer of lipids.
o Gram positive bacteria stain purple. These bacteria have a thicker layer of
peptidoglycan in the cell wall. Typically Gram + bacteria are easier to kill with
antibiotics.
Bacteria can evolve resistance
multi-drug resistant bacteria – serious public health issue resulting from inappropriate and
incomplete use of antibiotics
o called “superbugs”
o resistance is a result of natural selection – bacteria that are unaffected by an
antibiotic due to a random mutation survive to reproduce other bacteria that are also
resistant to the same antibiotic (binary fission)
o genes for resistance are acquired when plasmids are exchanged during conjugation
o factors contributing to this issue include:
 overuse – prescribing an antibiotic for a viral infection is just one example
 underuse – failing to take the entire course of antibiotics prescribed
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the weakest bacteria are destroyed first, leaving behind those that are more resistant
additional (the entire prescription) may kill all of the bacteria or reduce their numbers
to a load your immune system can handle
misuse – feeding them to livestock to increase their growth rate leads to
resistant bacteria present in the food as well as in the animals
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