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

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Presentation on theme: "Ch. 27 Bacteria and Archaea Objective: Understand the general structure and motility of bacteria and how genetic recombination increases diversity."— Presentation transcript:

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 o Gram positive: stains violet due to thick layer peptidoglycan. o 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 bacteria Outer membrane Peptido- glycan layer Plasma membrane Cell wall 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 o 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. o Division stops due to space limits, metabolic toxins, eaten, etc. o Short generation time leads to quick evolution.

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

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

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

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

12 Conjugation 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 1  m F plasmid Bacterial chromosome F  cell (donor) F  cell (recipient) Mating bridge Bacterial chromosome (a) Conjugation and transfer of an F plasmid Hfr cell (donor) F  cell (recipient) (b) Conjugation and transfer of part of an Hfr bacterial chromosome F factor AA AA AA AA AA AA AA F  cell AA AA Recombinant F  bacterium AA


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