KEY CONCEPT Bacteria and archaea are both single-celled prokaryotes.

1. KEY CONCEPT Bacteria and archaea are both single-celled prokaryotes.

2. Prokaryotes are widespread on Earth. • Prokaryotes can be grouped by their need for oxygen. • obligate anaerobesare poisoned byoxygen • obligate aerobes need oxygen • facultative aerobes can live with or without oxygen

3. Lactobacilli: rod-shaped Enterococci: spherical Spirochaeta: spiral Bacteria and archaea are structurally similar but have different molecular characteristics. • Bacteria commonly come in three forms. • rod-shaped, called bacilli • spiral, called spirilla or spirochetes • spherical, called cocci • Archaea have many shapes.

4. Archaea examples

6. pili plasmamembrane flagellum chromosome cell wall plasmid This diagram shows the typical structure of a prokaryote. Archaea and bacteria look very similar, although they have important molecular differences. • plasmid • flagellum • pili • Bacteria and archaea have similar structures.

7. GRAM NEGATIVE GRAM POSITIVE • The amount of peptidoglycan within the cell wall can differ between bacteria • Bacteria and archaea have molecular differences. • Archaea have different lipids entirely • Bacteria: have peptidoglycan in cell walls • Archaea: no peptidoglycan in cell walls

8. Gram-negative bacteria have a thin layer of peptidoglycan and stain red. Gram-positive bacteria have a thicker peptidoglycan layer and stain purple. • stains polymer peptidoglycan • gram-positive stains purple, more peptidoglycan • gram-negative stains red, less peptidoglycan • Gram staining identifies bacteria.

9. conjugation bridge TEM; magnification 6000x Bacteria have various strategies for survival. • Prokaryotes exchange genes during conjugation. • Bacteria may survive by forming endospores.

10. Anthrax – forms endospores