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:
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. (a) Spherical(b) Rod-shaped(c) Spiral 1 m 3 m
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.
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
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
Internal Organization and DNA Smaller, circular DNA found in nucleoid (not nucleus) with very small plasmids (self replicating DNA) Chromosome Plasmids 1 m
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.
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
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
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.
Transduction A “mutant” phage with bacterial DNA infects a bacteria cell. Recombinant cell Recipient cell Recombination AA AA AA BB BB AA Donor cell AA BB BB AA Phage
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 AA AA AA AA AA AA AA F cell AA AA Recombinant F bacterium AA