1. Chapter 20: Viruses and Prokaryotes
Section 20-2: Prokaryotes

2. Classifying Prokaryotes
Unicellular organisms that lack a nucleus
DNA free-floating
Two groups domains: Bacteria and Archae

3. Bacteria Larger domain No agreement about number of phyla
Live everywhere – fresh/salt water, land, within other eukaryotes, etc
Usually have a cell wall for shape and protection – contains peptidoglycan
Escherichia coli – found in human intestines – have extra membrane around cell wall for more protection
Flagella for movement, pili to anchor bacterium

4. E. coli

5. Archae Look similar to Bacteria under a microscope
Cell walls contain lipids
DNA more like eukaryotes
Many live in harsh/extreme environments – salt lakes, hot springs, no oxygen, etc

6. Structure and Function
Range in size from 1-5 micrometers
Come in three shapes:
Bacillus (pl. bacilli) – rod shaped
Coccus (pl. cocci) – spherical
Spirillum (pl. spirilla) – spiral/corkscrew shaped
Also three arrangements:
Diplo- (in a pair)
Staphlyo (in a bunch)
Strepto- (in a chain)

7. Shapes/Arrangements

8. Structure and Function
Can be distinguished by how and if they move – flagella, slime
Energy released during cellular respiration, fermentation, or both
Vary in the way they obtain energy

11. Growth, Reproduction, and Recombination
Binary fission occurs when a prokaryote has doubled in size – replicates its DNA and splits
Asexual reproduction
Can be very fast when conditions right
When conditions are unfavorable, many prokaryotes form endospores
Thick wall forms around DNA and part of cytoplasm
Can stay dormant from many years
Bacillus anthracis

12. Growth, Reproduction, and Recombination
Mutations allow prokaryotes to evolve - inherited through binary fission
Many prokaryotes also exchange genetic information through conjugation
Hollow bridge forms between 2 bacterial cells and genetic information (usually plasmids) move from one cell to another
Increases genetic diversity

13. Importance of Prokaryotes
Decomposers – break down complex organic molecules into simpler ones, supplying raw materials needed
Actinomycetes in soil
Sewage treatment
Water purification
Production of fertilizers
Producers – cyanobacteria responsible for photosynthesis in ponds/aquatic environments
Nitrogen fixers – convert atmospheric nitrogen gas into usable forms
Symbiotic relationships with plants – Rhizobium and legumes

14. Human Uses of Prokaryotes
Foods/commercial products (yogurt produced with Lactobacillus)
Digest petroleum
Remove human-made wastes and poisons from water
Synthesize drugs, chemicals by genetic engineering
Those adapted to extreme environments may produce heat-stable enzymes