1. Bacteria

2. Prokaryotes Single-celled organisms that do not have organelles
Commonly referred to as bacteria
3 shapes:
Rod shaped (bacillus)
Sphere shaped (coccus)
Spiral shape (spirillum)
Divided into two domains:
Domain Archaea
Domain Bacteria

3. Domain Archaea
Found in many places, including extreme environments (salt lakes & hot springs)
Structurally different from Bacteria
Some similar to eukaryotes; others unique among living organisms

4. Domain Bacteria Most prokaryotes belong to this domain
Found everywhere
One square inch of skin contains an average of 100,000 bacteria

5. Bacterial Structure
Bacterial DNA is a single chromosome called a nucleoid
Extra loops of DNA are called plasmids
Have cell walls made of a protein-carbohydrate compound called peptidoglycan
Gram-positive bacteria have thick layers of peptidoglycan & no outer membranes
Gram-negative bacteria have thin layers of peptidoglycan & outer membranes

6. Gram-Positive Bacteria
Gram stain contains a purple and a pink dye
Purple dye is applied first
The thick peptidoglycan layer of Gram-positive bacteria will absorb the purple dye, causing it to look purple after its been stained

7. Gram-Negative Bacteria
Does not have a thick layer of peptidoglycan
Outer membranes will not trap the purple dye, but will absorb the pink dye, causing it to look pink when stained
Outer membranes make them better able to resist host defenses & medicines

8. Obtaining Energy & Nutrients
Bacteria can be placed into 3 groups based on how they get energy & nutrients:
Photoautotrophs—get energy from sunlight through photosynthesis
Chemoautotrophs—get energy from inorganic sources; can make their own amino acids & proteins in the presence of hydrogen-rich chemicals
Heterotrophs—get their energy from other organisms

9. Reproduction & Adaptation
Binary Fission—asexual reproduction used by bacteria to create 2 identical cells from 1 original cell
Genetic Recombination—3 ways for bacteria to form new genetic combinations:
Conjugation—when 2 bacteria exchange genetic material

10. Reproduction & Adaptation, cont.
Transformation—when bacteria pick up DNA fragments from their environments
Transduction—when genetic material (plasmid) is transferred by a virus
Plasmids have resistance to antibiotics
Endospore Formation—when bacteria form thick-walled structures that surround their DNA & some of their cytoplasm
Can survive harsh conditions & lay dormant for hundreds of years before being revived