1' List unique characteristics that distinguish archaea from bacteria'

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1. List unique characteristics that distinguish
archaea from bacteria.

• Archaea
• Evolved from the earliest cells
• Inhabit only very extreme environments
• Only a few hundred species exist

• Bacteria
• The modern prokaryotes
• Over 10,000 species
• Differ structurally, biochemically, and
  physiologically from Archaea ?

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2. Describe the three domain system of
classification and explain how it differs from
previous systems.

• Domain Archaea ? Archaebacteria
• Domain Bacteria ? Eubacteria
• Domain Eukarya ? all eukaryotes
• domain is above the Kingdom taxon, and includes
  all taxa below ?

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3. Using a diagram, distinguish among the three
most common shapes of prokaryotes.

• Spheres (cocci)
• Rods (bacilli)
• Helices (spirilla spirochetes)

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4. Describe the structure and functions of
prokaryotic cell walls.

• 1. Maintain cell shape
• 2. Protect cell
• 3. Prevent cell from bursting
• Differ in chemical composition and construction
  than protists, plants and fungi
• Made of peptidoglycan ? modified sugar polymers
  crosslinked by short polypeptides (archaea dont
  have it) ?

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5. Distinguish between the structure and staining
properties of gram-positive and gram-negative
bacteria.

• Gram stain ? a stain used to distinguish two
  groups of bacteria by virtue of a structural
  difference in their cell walls
• Gram ? simple cell walls with lots of
  peptidoglycan
• - these stain blue in color
• Gram - ? more complex cell walls with less
  peptidoglycan
• - Outer lipopolysaccharide-containing membrane
  that covers the cell wall
• - these stain pink in color ?

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6. Explain why disease-causing gram-negative
bacterial species are generally more pathogenic
than disease-causing gram-positive bacteria.

• The lipopolysaccharides
• - these are often toxic and the outer membrane
  helps protect these bacteria from host defense
  systems
• - can impede the entry of drugs into the cells,
  making gram negative bacteria more resistant to
  antibiotics ?

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7. Describe three mechanisms motile bacteria use
to move.

• Flagella
• Filaments ? characteristic of spirochetes
• - spiral around cell inside cell wall and rotate
  like a corkscrew
• Gliding ? glide through a layer of slimy
  chemicals secreted by the organism
• - movement may result from flagellar motors that
  lack the flagellar filaments ?

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8. Explain how prokaryotic flagella work and why
they are not considered to be homologous to
eukaryotic flagella.

• Prokaryotic flagella are unique in structure and
  function
• They lack the 9 2 microtubular structure and
  rotate rather than whip back and forth
• They are not covered by plasma membrane
• They are 1/10 the width of eukaryotic flagella ?

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9. Indicate where photosynthesis and cellular
respiration take place in prokaryotic cells.

• Photosynthesis ? prokaryotes have specialized
  metabolic machinery with internal membranes and a
  light-harvesting pigment system
• Cellular respiration ? most prokaryotes use this,
  including saprobes and parasites
• Occurs in infoldings of the plasma membrane, like
  mitochondria ?

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10. Explain how the organization of the
prokaryotic genome differs from that in
eukaryotic cells.

• Lack diverse internal membranes of eukaryotes
• Genome has 1/1000 as much DNA as eukaryotes
• Has a genophore ? the bacterial chromosome (one
  strand of circular DNA)
• - concentrates in the nucleoid region with no
  surrounding nuclear membrane
• Has plasmids ? smaller rings of DNA with
  supplemental genes for functions like antibiotic
  resistance ?

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11. Explain what is meant by geometric growth.

• One cell divides into two, two divide into four,
  four into eight, etc
• Essentially, growth doubles with each generation ?

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12. List the sources of genetic variation in
prokaryotes.

• Transformation ? the process by which external
  DNA is incorporated by bacterial cells
• Conjugation ? the direct transfer of genes from
  one bacterium to another
• Transduction ? the transfer of genes between
  bacteria by viruses ?

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13. Distinguish between autotrophs and
heterotrophs.

• Autotrophs ? organisms that synthesize their food
  from inorganic molecules and compounds
• - Example Plants, cyanobacteria

• Heterotrophs ? organisms that require organic
  nutrients as their carbon source
• - Example Animals, some bacteria ?

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14. Describe four modes of bacterial nutrition
and give examples of each.

• Photoautotrophs ? use light energy to synthesize
  organic compounds from CO2
• - examples plants, cyanobacteria
• Chemoautotrophs ? require CO2 as a carbon source
  and obtain energy by oxidizing inorganic
  compounds like H2S, NH3, Fe2
• - example Archaea, Sulfobolus
• Photoheterotrophs ? use light to generate ATP
  from an organic carbon source (unique to some
  prokaryotes)
• Chemoheterotrophs ? must obtain organic molecules
  for energy and as a carbon source
• - examples most bacteria and most eukaryotes ?

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15. Distinguish among obligate aerobes,
facultative anaerobes and obligate anaerobes.

• Obligate aerobe ? prokaryotes that need O2 for
  cellular respiration
• Facultative anaerobe ? prokaryotes that use O2
  when present, but in its absence can grow using
  fermentation
• Obligate anaerobe ? prokaryotes that are poisoned
  by oxygen and live exclusively by fermentation
• - they use other inorganic molecules as electron
  acceptors (other than O2) ?

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16. Describe, with supporting evidence, plausible
scenarios for the evolution of metabolic
diversity of prokaryotes.

• The 1st prokaryotes must have been anaerobes and
  simple
• In the beginning, as ATP supplies were depleted,
  natural selection selected prokaryotes that could
  regenerate ATP from ADP, leading to glycolysis
  (no O2)
• The 1st prokaryotes were probably chemoautotrophs
  (rare in todays world) ?

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17. Explain how molecular systematics has been
used in developing a classification of
prokaryotes.

• By comparing energy metabolism
• Ribosomal RNA comparisons show prokaryotes
  diverged into Archaea and Bacteria lineages early
  the RNA indicates the presence of signature
  sequences domain-specific base sequences at
  comparable locations in ribosomal RNA or other
  nucleic acids
• Bottom line ? they found that Archaea have at
  least as much in common with eukaryotes as they
  do with bacteria ?

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18. List the three main groups of archaea,
describe distinguishing features among the groups
and give examples of each.

• Methanogens ? named for their unique form of
  energy metabolism
• - use H2 to reduce CO2 to CH4 (strict anaerobes)
• - important decomposers and digestive system
  symbionts with termites and herbivores
• Extreme halophiles ? like high salinity
  environments (15 20)
• - have the pigment bacteriorhodopsin in the
  plasma membrane
• - absorb light to pump H ions out
• Extreme thermophiles ? inhabit HOT environments
  (60 80 degrees Celsius)
• - one sulfur-metabolizing thermophile lives in
  105 C water by underwater hydrothermal vents ?

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19. List the major groups of bacteria, describe
their mode of nutrition, some characteristic
features and representative examples.

• Spirochetes ? helical chemoheterotrophs
  flagella ex Lyme disease
• Chlamydias ? obligate parasites gram cell
  walls most common STD causes blindness
• Gram positive ? some are gram but grouped here
  due to molecular systematics example
  Clostridium
• Cyanobacteria ? photoautotrophs example
  Anabaena
• Proteobacteria ?
• 1. Purple bacteria photoautotrophs Chromatium
• 2. Chemoautotrophic free-living and symbiotic
  Rhizobium
• 3. Chemoheterotrophic in intestinal tracts
  Ecoli, Salmonella ?

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20. Explain how endospores are formed and why
endospore-forming bacteria are important to the
food-canning industry.

• Endospore ? resistant cell formed by some
  bacteria contains one chromosome copy surrounded
  by a thick wall
• Original cell replicates chromosome and surrounds
  one copy with a durable wall
• Endospores can survive boiling water for a short
  time
• - special precautions must be taken to kill
  endospores of dangerous bacteria ?

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21. Explain how the presence of E. coli in public
water supplies can be used as an indicator of
water quality.

• E. coli is found in the intestines and excretion
  of animals and if found in drinking water or
  post-plant sewage, the sewage system is bad
  (leaking, etc) ?

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22. Explain why all life on earth depends upon
the metabolic diversity of prokaryotes.

• Earths metabolic diversity is greater among the
  prokaryotes than all of the eukaryotes
• The diversity is a result of adaptive radiation
  over billions of years
• Examples cyanobacteria make oxygen
• saprobes decompose dead
• materials ?

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23. Distinguish among mutualism, commensalism,
and parasitism.

• Mutualism ? symbiosis in which both symbionts
  benefit (/)
• Commensalism ? symbiosis in which one symbiont
  benefits while neither helping nor harming the
  other symbiont (/0)
• Parasitism ? symbiosis in which one symbiont (the
  parasite) benefits at the expense of the host
  (/-) ?

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24. List Kochs postulates that are used to
substantiate a specific pathogen as the cause of
a disease.

• Find the same pathogen in each diseased
  individual
• Isolate the pathogen from a diseased subject and
  grow it in a pure culture
• Use cultured pathogen to induce the disease in
  experimental animals
• Isolate the same pathogen in the diseased
  experimental animal ?

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25. Distinguish between exotoxins and endotoxins.

• Exotoxins ? proteins secreted by bacterial cells
• - can cause disease without the organism being
  present
• - these are among the most potent poisons
  (example botulism cholera)

• Endotoxins ? toxic component of outer membranes
  of some gram bacteria
• - usually induces fever and aches (example
  Salmonella) ?

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26. Describe how humans exploit the metabolic
diversity of prokaryotes for scientific and
commercial purposes.

• The range of purposes has increased through
  recombinant DNA technology
• Cultured bacteria to make vitamins and
  antibiotics
• Used as simple models of life to learn about
  metabolism and molecular biology
• Methanogens digest organic waste at sewage plants
• Decompose pesticides and other synthetic
  compounds
• Make products like acetone and butanol
• Convert milk into yogurts and cheeses for
  consumption ?

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27. Describe how Streptomyces can be used
commercially.

• Many of the antibiotics that we now use are
  produced naturally by members of the genus
  Streptomyces
• The End!!
• Study for the Chapter 26 27 Quiz! ?