Classifying Prokaryotes

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Classifying Prokaryotes
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Shapes of bacterial cells

• There are three categories based on the shape of
  individual cells.
• Cocci Rounded (spherical or ovoid)
• Bacilli Rod-shaped
• Spiral

• There are two spiral forms
• Spirilla Rigid helix
• Spirochete Flexible helix

• Other shape categories
• Vibrio Curved rod
• Coccobacillus Between cocci and bacillus
• Pleomorphic Varied shapes and sizes

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• List and define the three shape categories of
  bacteria.
• List and define the two spiral forms of bacteria.
• List and define the three other shape categories

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Groupings of bacterial cells

• Some cocci form groups
• Diplo Pairs
• Strepto Chains
• Tetrads Groups of four
• Sacina Cuboidal groups
• Staphylo Clusters

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• Define
• Diplo
• Strepto
• Tetrad
• Sarcina
• Staphyl

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Endospores

• Resting state able to survive adverse conditions.
• Formation
• Triggered by lack of nutrients.
• Form within membrane sac inside cell. Develops
  hard outer layers.
• Contains essentials Chromosome, ribosomes,
  proteins, small molecules.
• Characteristics
• Dehydrated
• Resistant to heat, chemicals, radiation,
  dehydration.
• Can survive boiling for hours
• Can survive bleach
• Its claimed that 250-million year old endospores
  were revived.
• Its claimed that 5 million year old spores from
  amber have been germinated.
• Only certain bacteria form endospores Examples
• Bacillus anthraxis. Antrax
• Clostridium tetani. Tetanus (lockjaw)
• Clostridium botulinum. Botulism (food
  poisoning). Source of botox.

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• What is an endospore?
• What triggers the formation of endospores?
• Briefly describe how endospores form.
• What are 3 conditions that endospores can resist?
• Give two examples of bacteria that can form
  endospores.

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Prokaryotic classification

• Modern classification of prokaryotes is based
  generally on gene sequences.

• Distances between dots represent relatedness.
• Major groups
• Archaea

• Thermophiles

• Halophiles

• Methanogens

• Bacteria

• Deeply-branching

• Phototropic

• Low G C Gram-positive

• High G C Gram-positive

• Gram-negative

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What are the two broadest categories of
prokaryotes?
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Prokaryotic classification Archaea

• No archaea are known to cause disease.
• Most archaea live in moderate environments but
  some are extremophiles (live in extreme
  environments). Examples
• Thermophiles. Live in hot environments such as
  geothermal pools (e.g.- Yellowstone National
  Park) or deep sea hydrothermal vents.

• Halophiles. Live in high salt environments such
  as Dead Sea, Great Salt Lake, evaporation ponds
  (for production of salt). Produce red or orange
  pigment.

• Methanogens
• Produce methane waste
• Obligate anaerobes
• Found in
• Sediments at bottoms of lakes and oceans. Large
  quantity of methane trapped.
• Guts of animals. Can produce 400 liters of gas
  per day in one cow.

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• Do archaea cause disease?
• What is an extremophile?
• Are most archaea extremophiles?
• What are the two types of extremophiles? Give an
  example of a habitat for each.
• What is the basis of the term methanogen?
• Give two examples of different types of habitats
  in which methanogens are found.

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Prokaryotic classification Deeply branching

• Believed to be similar to earliest bacteria.
  (Deep branch in evolutionary tree) Evidence based
  on characteristics
• Autotrophic. Earliest cells not likely to be
  heterotrophs because there would have been
  limited supply of limited supply of other
  organisms to consume.
• Habitats resemble likely habitats of early Earth
  Hot, anaerobic, exposed to intense radiation.
• Example Deinococcus radiodurans
• A poly-extremophile. Withstands multiple extreme
  conditions Cold, heat, dehydration, vacuum,
  acid and radiation.
• Can withstand 1000 times (or more) the radiation
  that would kill a human.
• Can help with disposal of solvents and heavy
  metals.
• Can survive in outer space!

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• What is the significance of the term deeply
  branching?
• List and briefly explain two characteristics of
  deeply branching bacteria that provide evidence
  to support the idea that they are similar to the
  earliest bacteria.

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Prokaryotic classification Phototropic

• Span multiple taxa (groups) but have in common
  the use of light for energy.
• Two major groups
• Cyanobacteria (blue-green bacteria)
• Green and purple phototropic bacteria
• Cyanobacteria
• Include cocci, discs, filaments
• Some glide along surfaces
• Some are nitrogen-fixers
• Believed to
• Be responsible for Earths oxygen atmosphere
• Be the ancestors of chloroplasts

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• What are the two major groups of phototropic
  bacteria?
• What are two ways in which Cyanobacteria have
  played important roles in evolution?

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Prokaryotic classification Phototropic

• Green and purple phototropic bacteria
• Do not generate oxygen from photosynthesis.
• Some are sulfur bacteria that obtain electrons
  for photosynthesis from hydrogen sulfide (H2S)
• Commonly live in hydrogen sulfide-rich mud at
  bottoms of lakes, ponds.
• Not necessarily green or purple but some are.

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Prokaryotic classification Gram Positive

• G C Classification
• Monomers for DNA A, G, C, T. Pairs G-C and
  A-T
• Species vary in proportion of G-C vs. A-T
• G-C level happens to correlate well with overall
  relatedness of Gram-positive bacteria.
• Gram-positive bacteria are hence divided into
• Low G C Gram-Positives
• High G C Gram-Positives

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Gram-positive bacteria are divided into Low G
C Gram-positives and High G C Gram-positives.
Explain.
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Prokaryotic classification Gram Positive

• Low G C Gram-Positive groups
• Clostrida
• Obligate anaerobes
• Form endospores
• Produce toxins
• Include several disease-causing species.
  Examples
• Clostridium tetani Causes tetanus
• Clostridium botulinum Causes botulism (food
  poisoning). Produces botulinum toxin (Botox)

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• What are two characteristics of Clostridia?
• Give two examples of Clostridia and the diseases
  they cause

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Prokaryotic classification Gram Positive

• Low G C Gram-Positive groups (continued)
• Mycoplasmas
• Smallest cells
• No cell walls (negative Gram stain) but more
  closely related to Gram-positives than
  Gram-negatives
• Pleomorphic
• Generally live in animal hosts
• Include species that cause pneumonia and urinary
  infections

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What are two characteristics of Mycoplasmas?
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Prokaryotic classification Gram Positive

• Low G C Gram-Positive groups (continued)
• Other Low G C bacilli and cocci
• Bacillus (refers to genus, not just shape)
• Often found in soil
• Form endospores
• Examples
• Bacillus anthracis Causes Anthrax

• Bacillus thuringiensis Produces protein (Bt
  toxin) toxic to caterpillars. Used as natural
  insecticide.

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Give an example of a member of the bacillus genus
and indicate its importance (disease caused or
practical use).
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Prokaryotic classification Gram Positive

• Low G C Gram-Positive groups (continued)
• Other Low G C bacilli and cocci (continued)
• Lactobacillus
• Found in digestive system, vagina. Protect
  against pathogens.
• Used in production of cheese, yogurt, pickles.
• Useful in treatment of diarrhea, milk allergies.
• Streptococcus and Enterococcus
• Include disease-causing forms Strep throat,
  pneuomia, Flesh-eating Streptococcus.
• Staphylococcus
• Includes common skin-dwelling Staphylococus
  aureus. Normally harmless but can cause disease
  (skin infections, pneumonia, food poisoning)

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• Lactobacillus
• Lactobacillus is used in the production of what
  three products?
• What is the role of Lactobacillus in the body?
• List two diseases causes by Streptococcus.
• List two diseases caused by Staphylococcus.

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Prokaryotic classification Gram Positive

• High G C Gram-Positive groups
• Mycobacterium
• Slow-growing
• Can take a month or more for colonies to appear
  compared to overnight for many other bacteria.
• Waxy cell wall. Require acid-fast stain.
• Include pathogens
• Mycobacterium tuberculosis Tuberculosis
• Mycobacterium leprae Leprosy
• Actinomycetes
• Norcardia Can degrade a number of pollutants.
• Streptomyes
• Breakdown/recycle many nutrients in soil.
• Gives soils its must smell.
• Source of a number of antibiotics.

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• Give two characteristics of mycobacterium.
• List two diseases caused by mycobacterium
  species.
• Give two ways in which Streptomyces is important.

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Prokaryotic classification Gram Negative

• Selected examples
• Nitrogen fixers
• Capture nitrogen gas from the atmosphere, making
  it available for the ecosystems of the world.
• Example Rhizobium. Lives in nodules on the
  roots of certain plants (legumes, clover).

• Agrobacterium
• Infects plants. Carries gene for plant growth
  hormone resulting in growth of gall (abnormal
  growth) on the plant
• Engineered for genetic engineering of plants.

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Prokaryotic classification Gram Negative

• Selected examples (continued)
• Rickettsia
• Small bacteria that live inside of mammalian
  cells
• Rickettsial diseases Typhus, Rocky Mountain
  Spotted Fever
• Neisseria gonorrhoeae Gonorrhea
• Escherichia coli Harmless inhabitant of
  digestive system. Rare forms cause disease.
• Helicobacter pylori Ulcers
• Treponema pallidum Syphilis

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• What disease is caused by each
• Rickettsia
• Helicobacter pylori
• Treponema pallidum