Chapter 27

  • View
    14

  • Download
    0

Embed Size (px)

DESCRIPTION

Chapter 27. Bacteria and Archaea. Overview: Masters of Adaptation. They are prokaryotes They thrive almost everywhere, including places too acidic, salty, cold, or hot for most other organisms Most prokaryotes are microscopic, but what they lack in size they make up for in numbers - PowerPoint PPT Presentation

Text of Chapter 27

  • Fig. 27-1

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Concept 27.1: Structural and functional adaptations contribute to prokaryotic successMost prokaryotes are unicellular, although some species form coloniesMost prokaryotic cells are 0.55 m, much smaller than eukaryotic cellsProkaryotic cells have a variety of shapesThe three most common shapes are spheres (cocci), rods (bacilli), and spirals

  • Fig. 27-2(a) Spherical (cocci)1 m(b) Rod-shaped (bacilli)2 m(c) Spiral5 m

  • I. Concept 27.1: Structure, Function, and Reproduction of ProkaryotesGroupingsstreptochains staphyloclustersdiplopairs*

  • *

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Cell-Surface StructuresAn important feature of nearly all prokaryotic cells is their cell wall, which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environmentEukaryote cell walls are made of cellulose or chitinBacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Walls of Archaea contain polysaccharides and proteins but lack peptidoglycanCell membrane is internal to cell wall, but other substances may be external to the cell wallUsing the Gram stain, scientists classify many bacterial species into Gram-positive and Gram-negative groups based on cell wall composition

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Gram-negative bacteria have less peptidoglycan and an outer membrane that can be toxic, and they are more likely to be antibiotic resistantMany antibiotics target peptidoglycan and damage bacterial cell walls

  • Fig. 27-3CellwallPeptidoglycanlayerPlasma membraneProteinGram-positivebacteria(a) Gram-positive: peptidoglycan traps crystal violet.Gram-negativebacteria(b) Gram-negative: crystal violet is easily rinsed away, revealing red dye.20 mCellwallPlasma membraneProteinCarbohydrate portionof lipopolysaccharideOutermembranePeptidoglycanlayer

  • Fig. 27-3aCellwallPeptidoglycanlayerPlasma membraneProtein(a) Gram-positive: peptidoglycan traps crystal violet.

  • Fig. 27-3bCellwallPeptidoglycanlayerPlasma membraneProtein(b) Gram-negative: crystal violet is easily rinsed away, revealing red dye.OutermembraneCarbohydrate portionof lipopolysaccharide

  • Fig. 27-3cGram-positivebacteriaGram-negativebacteria20 m

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    A polysaccharide or protein layer called a capsule covers many prokaryotes

  • Fig. 27-4Capsule200 nm

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Some prokaryotes have fimbriae (also called attachment pili), which allow them to stick to their substrate or other individuals in a colonySex pili are longer than fimbriae and allow prokaryotes to exchange DNA

  • Fig. 27-5Fimbriae200 nm

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    MotilityMost motile bacteria propel themselves by flagella that are structurally and functionally different from eukaryotic flagellaIn a heterogeneous environment, many bacteria exhibit taxis, the ability to move toward or away from certain stimuli

  • Fig. 27-6FlagellumFilamentHookBasal apparatusCell wallPlasmamembrane50 nm

  • Fig. 27-6bProkaryotic flagellum (TEM)50 nm

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Internal and Genomic OrganizationProkaryotic cells usually lack complex compartmentalizationSome cells use specialized membranes (infoldings of the plasma membrane) to perform metabolic functions such as cellular respiration and photosynthesisSome prokaryotes do have specialized membranes that perform metabolic functions

  • Fig. 27-7(a) Aerobic prokaryote(b) Photosynthetic prokaryoteThylakoidmembranesRespiratorymembrane0.2 m1 m

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    The prokaryotic genome has less DNA than the eukaryotic genomeMost of the genome consists of a circular chromosome Typically, the genome is non membrane bound and located in the nucleoid regionSome species of bacteria also have smaller rings of DNA called plasmids

  • Fig. 27-8ChromosomePlasmids1 m

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Reproduction and AdaptationProkaryotes reproduce quickly by binary fission and can divide every 13 hoursMany prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuriesForm when an essential nutrient is lacking in the environmentReplicate the chromosome and surround it with a durable wall

  • Fig. 27-9Endospore0.3 m

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Prokaryotes can evolve rapidly because of their short generation times

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Prokaryotes have considerable genetic variationThree factors contribute to this genetic diversity:Rapid reproductionMutationGenetic recombinationConcept 27.2: Rapid reproduction, mutation, and genetic recombination promote genetic diversity in prokaryotes

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Rapid Reproduction and MutationProkaryotes reproduce by binary fission, and offspring cells are generally identicalMutation rates during binary fission are low, but because of rapid reproduction, mutations can accumulate rapidly in a populationHigh diversity from mutations allows for rapid evolution

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Genetic RecombinationAdditional diversity arises from genetic recombinationProkaryotic DNA from different individuals can be brought together by transformation, transduction, and conjugation

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Transformation and TransductionA prokaryotic cell can take up and incorporate foreign DNA from the surrounding environment in a process called transformationTransduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria)

  • Fig. 27-11-1DonorcellA+B+A+B+Phage DNA

  • Fig. 27-11-2A+DonorcellA+B+A+B+Phage DNA

  • Fig. 27-11-3RecipientcellBA+ARecombinationA+DonorcellA+B+A+B+Phage DNA

  • Fig. 27-11-4Recombinant cellRecipientcellA+BBA+ARecombinationA+DonorcellA+B+A+B+Phage DNA

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Conjugation and PlasmidsConjugation is the process where genetic material is transferred between bacterial cellsSex pili allow cells to connect and pull together for DNA transferA piece of DNA called the F factor is required for the production of sex piliThe F factor can exist as a separate plasmid or as DNA within the bacterial chromosome

  • Fig. 27-12Sex pilus1 m

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    The F Factor as a PlasmidCells containing the F plasmid function as DNA donors during conjugationCells without the F factor function as DNA recipients during conjugationThe F factor is transferable during conjugation

  • Fig. 27-13F plasmidF+ cellF cellMatingbridgeBacterial chromosomeBacterialchromosome(a) Conjugation and transfer of an F plasmidF+ cellF+ cellF cell(b) Conjugation and transfer of part of an Hfr bacterial chromosomeF factorHfr cellA+A+A+A+A+AAAAA+RecombinantF bacterium

  • Fig. 27-13-1F plasmidF+ cellF cellMatingbridgeBacterial chromosomeBacterialchromosome(a) Conjugation and transfer of an F plasmid

  • Fig. 27-13-2F plasmidF+ cellF cellMatingbridgeBacterial chromosomeBacterialchromosome(a) Conjugation and transfer of an F plasmid

  • Fig. 27-13-3F plasmidF+ cellF cellMatingbridgeBacterial chromosomeBacterialchromosome(a) Conjugation and transfer of an F plasmidF+ cellF+ cell

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    The F Factor in the ChromosomeA cell with the F factor built into its chromosomes functions as a donor during conjugationThe recipient becomes a recombinant bacterium, with DNA from two different cellsIt is assumed that horizontal gene transfer is also important in archaea

  • Fig. 27-13-4F factorHfr cell(b) Conjugation and transfer of part of an Hfr bacterial chromosomeA+AF cellA+A+A

  • Fig. 27-13-5F factorHfr cell(b) Conjugation and transfer of part of an Hfr bacterial chromosomeA+AF cellA+A+AA+A+A

  • Fig. 27-13-6F factorHfr cell(b) Conjugation and transfer of part of an Hfr bacterial chromosomeA+AF cellA+A+AA+A+ARecombinantF bacteriumAA+

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    R Plasmids and Antibiotic ResistanceR plasmids carry genes for antibiotic resistanceAntibiotic resistant strains of bacteria are becoming more common

    Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

    Concept 27.3: Diverse nutritional and metabolic adaptations have evolved in prokaryotesPhototrophs obtain energy from lightChemotrophs obtain energy from chemicalsAutotrophs require CO2 as a carbon sourceHeterotrophs require an organic nutrient to make organic compoundsThese factors can be combined to give the four major modes of nutrition: photoautotrophy, chemoautotrophy, photoheterotrophy, and chemoheterotrophy