1. Bacteria
Chapter 18
Section 2

2. Life History and Ecology
Bacteria consist of only a single cell
They may be found on the tops of mountains, the bottom of the deepest oceans, in the guts of animals, and even in the frozen rocks and ice of Antarctica.

3. Life History and Ecology (cont…)
They "eat" everything from sugar and starch to sunlight, sulfur and iron.
There's even a species of bacteria—Deinococcus radiodurans—that can withstand blasts of radiation 1,000 times greater than would kill a human being.

4. Classification Bacteria all are of the cell type called Prokaryotes
They are found in the Kingdoms Eubacteria & Archeabacteria

5. Grouping Bacteria
Most bacteria may be placed into one of three groups based on their response to gaseous oxygen.
Aerobic (Obligate Aerobes)
Thrive in the presence of oxygen and require it for their continued growth and existence
Anaerobic (Obligate Anaerobes)
Cannot tolerate gaseous oxygen
Facultative Anaerobes
Prefer growing in the presence of oxygen, but can continue to grow without it

6. Grouping Bacteria (cont…)
Bacteria may also be classified both by the mode by which they obtain their energy.
Heterotrophs
Break down complex organic compounds that they get from the environment
Includes:
Bacteria found in decaying material
Those that do fermentation or respiration
Autotrophs
Fix carbon dioxide to make their own food source
May be fueled by:
Light energy (photoautotrophic),
Oxidation of nitrogen, sulfur, or other elements (chemoautotrophic)

7. Autotrophic Bacteria ▲
Heterotrophic Bacteria ►

8. Heterotrophic Bacteria
Autotrophic Bacteria

9. Grouping Bacteria (cont…)
The cell membrane is surrounded by a cell wall in most bacteria
The composition of the cell wall varies among species and is an important character for identifying and classifying bacteria
Some bacteria retain a purple color when stained with a dye known as crystal violet, and are known as Gram-positive
Other bacteria have double cell walls, with a thin inner wall of peptidoglycan and an outer wall of carbohydrates, proteins, and lipids. Such bacteria do not stain purple with crystal violet and are known as Gram-negative

10. Gram Staining

11. What They Look Like A more or less typical bacterium, shown here, is
comparatively much simpler than a
typical eukaryotic cell.

12. What They Look Like (cont…)
All bacteria are basically one of three different shapes:
Rod- or stick-shaped and called bacilli
Shaped like little balls and called cocci
Helical or Spiral in shape