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Ch. 27 Bacteria and Archaea

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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. (a) Spherical (b) Rod-shaped (c) Spiral 1 m 3 m

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. Gram-positive bacteria Peptido- glycan layer Cell wall Plasma membrane 10 m Gram-negative Outer Plasma membrane Carbohydrate portion of lipopolysaccharide (b) Gram-negative bacteria: crystal violet is easily rinsed away, revealing red dye.

4 Motility 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. Flagellum Hook Motor Filament Rod Peptidoglycan layer Plasma membrane Cell wall 20 nm

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

6 Internal Organization and DNA
Smaller, circular DNA found in nucleoid (not nucleus) with very small plasmids (self replicating DNA) Chromosome Plasmids 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. Coat Endospore 0.3 m

9 3 mechanisms for prokaryotic genome combinations
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 Recombinant cell Recipient cell Recombination A A B Donor cell B Phage A “mutant” phage with bacterial DNA infects a bacteria cell.

12 Conjugation Sex pilus 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. F plasmid Bacterial chromosome F cell (donor) F cell (recipient) Mating bridge Bacterial chromosome (a) Conjugation and transfer of an F plasmid Hfr cell (b) Conjugation and transfer of part of an Hfr bacterial chromosome F factor A A Recombinant F bacterium

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