Bacteria are some of the oldest life forms on Earth, with fossil evidence placing their emergence at around 3.5 billion years ago. They are classified into two kingdoms, Archaea and Eubacteria, based on rRNA sequencing. While Archaea and Eubacteria both lack nuclei, they differ in their cell wall structure - Archaea have no peptidoglycan but special lipids, while Eubacteria contain peptidoglycan. Eubacteria are further classified by their shape as cocci, bacilli, or spirilla and differentiated as Gram positive or Gram negative based on their staining properties related to cell wall thickness.

1. Bacteria

2. Bacterial History The first cells in existence Fossils exist for prokaryotes 3.5 billion years ago Most bacteria autotrophic Pathogenic bacteria make up only a small percentage of total bacterial species

3. Classification Separated into two kingdoms based on rRNA sequencing Archea/Archaebacteria Bacteria/Eubacteria Traditionally grouped by structure and physiology, and reaction to stains

4. Archeabacteria Cell walls contain no peptidoglycan, do contain special lipids First found in Extreme environments, but now found everywhere

5. Archeabacteria Three Major Types Methanogens- harvest energy by converting CO2 and H2 into methane gas Extreme Halophiles- Salt loving bacteria, use the difference in concentration to generate ATP Thermoacidophiles- Live in very hot very acidic places, like near underwater volcanic vents

6. Eubacteria Have one of three major shapes Cocci Bacilli Spirilla

7. Eubacteria- Gram Staining Process designed to differentiate between cell wall types Gram Positive Purple Thick peptidoglycan Layer Gram Negative Pink Thin peptidoglycan layer Double lipid membrane