Presentation on theme: "Ch. 27 Bacteria and Archaea"— Presentation transcript:
1Ch. 27 Bacteria and Archaea Objective:Understand the general structure and motility of bacteria and how genetic recombination increases diversity.
227.1 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) Spiral1 m3 m
3Cell 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 peptidoglycanGram 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-positivebacteriaPeptido-glycanlayerCellwallPlasmamembrane10 mGram-negativeOuterPlasma membraneCarbohydrate portionof lipopolysaccharide(b) Gram-negative bacteria: crystal violet is easily rinsedaway, revealing red dye.
4MotilityAbout half of known bacteria can move (taxis) toward/away from a stimulusMost commonly via flagella either surrounding the body or found at 1 end. Works like a helicopter with a motor, hook, and filament.FlagellumHookMotorFilamentRodPeptidoglycanlayerPlasmamembraneCell wall20 nm
5Internal Organization and DNA No membrane bound organelles but plasma membrane folds on itself to make metabolic membranes.(a) Aerobic prokaryote(b) Photosynthetic prokaryoteRespiratorymembraneThylakoidmembranes0.2 m1 m
6Internal Organization and DNA Smaller, circular DNA found in nucleoid (not nucleus) with very small plasmids (self replicating DNA)ChromosomePlasmids1 m
7Reproduction 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.
8Reproduction and Adaptation Endospores develop in harsh conditions.Duplicated DNA in a tough, multilayered structure.Water is removed and metabolism stops.CoatEndospore0.3 m
93 mechanisms for prokaryotic genome combinations 27.2 Rapid Reproduction, Mutation, and Genetic Recombination Promote Genetic Diversity in Prokaryotes3 mechanisms for prokaryotic genome combinationsTransformationTransductionConjugation
10Transformation 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.
11TransductionRecombinant cellRecipientcellRecombinationAABDonor cellBPhageA “mutant” phage with bacterial DNA infects a bacteria cell.
12ConjugationSex pilus1 mA 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 plasmidBacterial chromosomeF cell(donor)F cell(recipient)MatingbridgeBacterialchromosome(a) Conjugation and transfer of an F plasmidHfr cell(b) Conjugation and transfer of part of an Hfr bacterial chromosomeF factorAARecombinantF bacterium