Ch. 27 Bacteria and Archaea
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Ch. 27 Bacteria and Archaea. Objective: Understand the general structure and motility of bacteria and how genetic recombination increases diversity. 27.1 Structural and Functional Adaptations Contribute to Prokaryotic Success. Very adaptable (extreme salt, pH, and temp).
Ch. 27 Bacteria and Archaea
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Ch. 27 Bacteria and Archaea Objective: Understand the general structure and motility of bacteria and how genetic recombination increases diversity.
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
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
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
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
Internal Organization and DNA Plasmids Chromosome • Smaller, circular DNA found in nucleoid (not nucleus) with very small plasmids (self replicating DNA) 1 m
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.
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
27.2 Rapid Reproduction, Mutation, and Genetic Recombination Promote Genetic Diversity in Prokaryotes • 3 mechanisms for prokaryotic genome combinations • Transformation • Transduction • Conjugation
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.
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
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
