Transcript 1. List unique characteristics that distinguish archaea from bacteria.

PROKARYOTES
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 
2. Describe the three domain system of
classification and explain how it differs
from previous systems.
1. Domain Archaea  Archaebacteria
2. Domain Bacteria  Eubacteria
3. Domain Eukarya  all eukaryotes

“domain” is above the Kingdom taxon, and
includes all taxa below 
3. Using a diagram, distinguish among the
three most common shapes of prokaryotes.
1. Spheres (cocci)
2. Rods (bacilli)
3. Helices (spirilla & spirochetes)
4. Describe the structure and functions of
prokaryotic cell walls.
1. Maintain cell shape
2. Protect cell
3. Prevent cell from bursting (hypotonic)
 Differ in chemical composition and
construction than protists, plants and fungi
 Made of peptidoglycan  modified sugar
polymers crosslinked by short polypeptides
(archaea don’t have it) 
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 
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 
7. Describe three mechanisms motile
bacteria use to move.
1. Flagella
2. Filaments  characteristic of spirochetes
- spiral around cell inside cell wall and
rotate like a corkscrew
3. Gliding  glide through a layer of slimy
chemicals secreted by the organism
- movement may result from flagellar
motors that lack the flagellar filaments 
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 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 
9. 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 
10. 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 
11. Describe four modes of bacterial
nutrition and give examples of each.
1.
2.
3.
4.
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 
12. 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 
13. List the three main groups of archaea,
describe distinguishing features among the
groups and give examples of each.
1.
2.
3.
Methanogens  named for their unique form of energy
metabolism
- important decomposers and in digestive system of
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 
14. List the major groups of bacteria, describe
their mode of nutrition, some characteristic
features and representative examples.
1.
2.
3.
4.
5.
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 
15. 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) 
16. Explain why all life on earth depends
upon the metabolic diversity of
prokaryotes.
 Earth’s 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 
17. Describe how humans exploit the
metabolic diversity of prokaryotes for
scientific and commercial purposes.

1.
2.
3.
4.
5.
6.
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 
18. Describe how Streptomyces can be
used commercially.
 Many of the antibiotics that we now use are
produced naturally by members of the genus
Streptomyces