Ch. 27 Bacteria and Archaea

1. Ch. 27 Bacteria and Archaea Objective: Understand the general structure and motility of bacteria and how genetic recombination increases diversity.

2. 27.1 Structural and Functional Adaptations Contribute to Prokaryotic Success • Very adaptable (extreme salt, pH, and temp). • Most are unicellular (0.5-5 um) but still perform all of life’s functions. 1 m 1 m 3 m (a) Spherical (b) Rod-shaped (c) Spiral

3. Cell Surface Structures • All bacteria have a cell wall. • Archaeal bacteria do NOT have a layer of peptidoglycan in their cell walls. • Eubacteria have differing amount of peptidoglycan • Gram positive: stains violet due to thick layer peptidoglycan. • Gram negative: stains red due to extra membrane past peptidoglycan. (a) Gram-positive bacteria: peptidoglycan traps crystal violet. (b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye. Gram-positive bacteria Gram-negative bacteria Carbohydrate portion of lipopolysaccharide Peptido- glycan layer Outer membrane Cell wall Cell wall Peptido- glycan layer Plasma membrane Plasma membrane 10 m

4. Motility Flagellum • About half of known bacteria can move (taxis) toward/away from a stimulus • Most commonly via flagella either surrounding the body or found at 1 end. Works like a helicopter with a motor, hook, and filament. 20 nm Filament Hook Motor Cell wall Peptidoglycan layer Plasma membrane Rod

5. Internal Organization and DNA 1 m 0.2 m • No membrane bound organelles but plasma membrane folds on itself to make metabolic membranes. Respiratory membrane Thylakoid membranes (a) Aerobic prokaryote (b) Photosynthetic prokaryote

6. Internal Organization and DNA Plasmids Chromosome • Smaller, circular DNA found in nucleoid (not nucleus) with very small plasmids (self replicating DNA) 1 m

7. Reproduction and Adaptation • Reproduce every couple of hours (under optimal conditions) by binary fission. • Division stops due to space limits, metabolic toxins, eaten, etc. • Short generation time leads to quick evolution.

8. Reproduction and Adaptation • Endospores develop in harsh conditions. • Duplicated DNA in a tough, multilayered structure. • Water is removed and metabolism stops. Endospore Coat 0.3 m

9. 27.2 Rapid Reproduction, Mutation, and Genetic Recombination Promote Genetic Diversity in Prokaryotes • 3 mechanisms for prokaryotic genome combinations • Transformation • Transduction • Conjugation

10. Transformation • Changes genotype and phenotype by uptake of foreign DNA • Ex: harmless strains of the bacteria that can cause pneumonia become pathogenic if they come in contact with a pathogenic cell.

11. Transduction Phage A B Donor cell • A “mutant” phage with bacterial DNA infects a bacteria cell. A B A Recombination A Recipient cell A B Recombinant cell A B

12. Conjugation 1 m • A donor bacteria makes a copy of its DNA, attaches to another bacteria via a (sex) pilus, the DNA travels to recipient forming a recombined cell. Sex pilus Bacterial chromosome F plasmid F cell (donor) F cell Mating bridge F cell (recipient) F cell Bacterial chromosome (a) Conjugation and transfer of an F plasmid Hfr cell (donor) A A A A A A F factor Recombinant F bacterium A A A A F cell (recipient) (b) Conjugation and transfer of part of an Hfr bacterial chromosome