1. The Prokaryotes Differences from Eukaryotes:
small cells (about 1/10 the size of eukaryotes)
no nuclear envelope
no membrane-bound organelles (e.g mitochondria)
smaller ribosomes than eukaryotes
little or no cytoskeleton
“naked” DNA – not associated with histone proteins
one main chromosome that is circular (not linear)
sometimes smaller circles of DNA called plasmids

2. Prokaryotic movement
Flagella do NOT have the “9+2” microtubule arrangement seen in eukaryotes.
Instead, the flagella are made of a single rod of a protein called flagellin.
The flagellum does not “whip” like eukaryotes; instead it rotates in its base – one of the only true rotational structures in living things.

3. Prokaryotic energy metabolism: extremely diverse!
Autotrophs –
Photoautotrophs
Chemoautotrophs*
Heterotrophs –
Photoheterotrophs*
Chemoheterotrophs
*no equivalent for these groups among eukaryotes

4. Autotrophs – get energy without relying on other living things
Photoautotrophs
Photosynthetic
Energy from sunlight, carbon from CO2
Basically the same energy metabolism as plants
Chemoautotrophs
Energy from inorganic sources (iron, sulfur, etc.)
Carbon from CO2
Sometimes called “chemosynthetic”

5. Heterotrophs – depend on other living things for energy
Photoheterotrophs
Like a very strange type of photosynthesis
Energy still comes from sunlight
Carbon comes from decomposing other living things
Chemoautotrophs
Energy and carbon both come from other living things
Basically same energy metabolism as animals & fungi

6. Chemoheterotrophs include:
Saprotrophs
decomposers and other decay-causing organisms
Mutualists
e.g. rumen bacteria in cows; N-fixing bacteria in beans
Commensals
live on another living thing, but don’t affect it
Parasites and Pathogens

7. Taxonomy of the prokaryotes
Controversial and currently in a state of major revision as molecular data are incorporated.
Formerly all grouped together in a single kingdom, called “Monera”
Now we realize that there are two main groups, Bacteria and Archaea.
Together with the Eukarya, these are recognized as the 3 main Domains of living things.

9. Relationships among the domains
Bacteria and Archaea are both considered prokaryotic because they lack organelles.
BUT: They diverged a very long time ago, and they are really quite different.
IN FACT: Archaea are more closely related to Eukarya than they are to Bacteria.

11. Cyanobacteria - Photoautotrophs

12. Spirochetes and Chamydias

13. Archaea Thermophiles – high temperatures Acidophiles – very low pH
Halophiles – very salty environments
Methanogens – methane producers