2 Ch. 27 ~ Prokaryotes Overview: They’re (Almost) Everywhere! Most prokaryotes are microscopicBut what they lack in size they more than make up for in numbersThe number of prokaryotes in a single handful of fertile soilIs greater than the number of people who have ever lived
3 Prokaryotes thrive almost everywhere Including places too acidic, too salty, too cold, or too hot for most other organismsFigure 27.1
4 27.1 ~ Structural, functional, and genetic adaptations contribute to prokaryotic success Most prokaryotes are unicellularAlthough some species form coloniesProkaryotic cells have a variety of shapesThe three most common of which are spheres (cocci), rods (bacilli), and spirals1 m2 m5 m(a) Spherical (cocci)(b) Rod-shaped (bacilli)(c) Spiral
5 Cell-Surface Structures One of the most important features of nearly all prokaryotic cellsIs their cell wall, which maintains cell shape, provides physical protection, and prevents the cell from bursting in a hypotonic environment
6 Using a technique called the Gram stain Scientists can classify many bacterial species into two groups based on cell wall composition, Gram-positive and Gram-negative(a)Gram-positive. Gram-positive bacteria havea cell wall with a large amount of peptidoglycanthat traps the violet dye in the cytoplasm. Thealcohol rinse does not remove the violet dye,which masks the added red dye.(b)Gram-negative. Gram-negative bacteria have lesspeptidoglycan, and it is located in a layer between theplasma membrane and an outer membrane. Theviolet dye is easily rinsed from the cytoplasm, and thecell appears pink or red after the red dye is added.Figure 27.3a, bPeptidoglycanlayerCell wallPlasma membraneProteinGram-positivebacteria20 mOutermembraneLipopolysaccharidenegative
7 The cell wall of many prokaryotes Is covered by a capsule, a sticky layer of polysaccharide or protein200 nmCapsuleFigure 27.4
8 Some prokaryotes have fimbriae and pili Which allow them to stick to their substrate or other individuals in a colony200 nmFimbriaeFigure 27.5
9 Motility Most motile bacteria propel themselves by flagella Which are structurally and functionally different from eukaryotic flagellaFlagellumFilamentHookCell wallPlasmamembraneBasal apparatus50 nmFigure 27.6
10 Internal and Genomic Organization Prokaryotic cellsUsually lack complex compartmentalizationSome prokaryotesDo have specialized membranes that perform metabolic functions(a) Aerobic prokaryote(b) Photosynthetic prokaryote0.2 m1 mRespiratorymembraneThylakoidmembranesFigure 27.7a, b
11 The typical prokaryotic genome Is a ring of DNA that is not surrounded by a membrane and that is located in a nucleoid regionFigure 27.81 mChromosome
12 Some species of bacteria Also have smaller rings of DNA called plasmidsDraw a prokaryotic cell and label the DNA and plasmidsProkaryotes reproduce quickly by binary fissionAnd can divide every 1–3 hoursMany prokaryotes form endosporesWhich can remain viable in harsh conditions for centuriesEndospore0.3 mFigure 27.9
13 27.2A great diversity of nutritional and metabolic adaptations have evolved in prokaryotesExamples of all four models of nutrition are found among prokaryotes:List Energy source & Carbon source:PhotoautotrophyChemoautotrophyPhotoheterotrophyChemoheterotrophy
14 Major nutritional modes in prokaryotes Table 27.1
15 27.3 Molecular systematics is illuminating prokaryotic phylogeny Until the late 20th centurySystematists based prokaryotic taxonomy on phenotypic criteriaApplying molecular systematics to the investigation of prokaryotic phylogenyHas produced dramatic results
16 A tentative phylogeny of some of the major taxa of prokaryotes based on molecular systematics Domain BacteriaDomainArchaeaEukaryaAlphaBetaGammaEpsilonDeltaProteobacteriaChlamydiasSpirochetesCyanobacteriaGram-positivebacteriaKorarchaeotesEuryarchaeotesCrenarchaeotesNanoarchaeotesEukaryotesUniversal ancestorFigure 27.12
17 Bacteria Diverse nutritional types The two largest groups are Are scattered among the major groups of bacteriaThe two largest groups areThe proteobacteria and the Gram-positive bacteria
18 Chlamydias, spirochetes, Gram-positive bacteria, and cyanobacteria Chlamydia (arrows) inside ananimal cell (colorized TEM)5 mLeptospira, a spirochete(colorized TEM)5 m1 mHundreds of mycoplasmascovering a human fibroblast cell(colorized SEM)Streptomyces, the source ofmany antibiotics (colorized SEM)50 mFigure 27.13Two species of Oscillatoria,filamentous cyanobacteria (LM)
19 Archaea Archaea share certain traits with bacteria Table 27.2Archaea share certain traits with bacteriaAnd other traits with eukaryotes
20 Some archaea live in extreme environments Extreme thermophiles thrive in very hot environmentsExtreme halophiles live in high saline environmentsColorful “salt-loving” archae live in these ponds near San Fransisco. Used for commercial salt production.MethanogensLive in swamps and marshes and produce methane as a waste product
21 27.4 Prokaryotes play crucial roles in the biosphere Chemical RecyclingProkaryotes play a major role in the continual recycling of chemical elements between the living and nonliving components of the environment in ecosystemsChemoheterotrophic prokaryotes function as decomposersBreaking down corpses, dead vegetation, and waste productsNitrogen-fixing prokaryotesAdd usable nitrogen to the environment
22 Symbiotic Relationships Many prokaryotes -Live with other organisms in symbiotic relationships such as mutualism and commensalismFigure 27.15
23 27.5 Prokaryotes have both harmful and beneficial impacts on humans Some prokaryotes are human pathogensBut many others have positive interactions with humansProkaryotes cause about half of all human diseasesLyme disease is an example5 µmFigure 27.16
24 Prokaryotes in Research and Technology Experiments using prokaryotes have led to important advances in DNA technologyProkaryotes are the principal agents in bioremediationThe use of organisms to remove pollutants from the environmentProkaryotes are also major tools inMining, the synthesis of vitamins, production of antibiotics, hormones, and other products
25 Ch. 28 ~ Protists28.1: Protists are an extremely diverse assortment of eukaryotesProtists are more diverse than all other eukaryotesAnd are no longer classified in a single kingdomMost protists are unicellular, colonial or multicellular
26 Protists, the most nutritionally diverse of all eukaryotes, include Photoautotrophs, which contain chloroplastsHeterotrophs, which absorb organic molecules or ingest larger food particlesMixotrophs, which combine photosynthesis and heterotrophic nutrition
27 There is now considerable evidence that much of protist diversity has its origins in endosymbiosis
29 28.3: Euglenozoans have flagella with a unique internal structure Euglenozoa is a diverse clade that includesPredatory heterotrophs, photosynthetic autotrophs, and pathogenic parasites
30 Ciliates, a large varied group of protists DinoflagellatesAre a diverse group of aquaticphotoautotrophs and heterotrophsAre abundant components of bothmarine and freshwater phytoplanktonCiliates, a large varied group of protistsAre named for their use of cilia to move and feedHave large macronuclei and small micronucleiConjugation – Two cells exchange haploid micronuclei (similar to prokaryotic conjugation).**Produces genetic variation
32 28. 5 Hairy and smooth flagella 1 28.5 Hairy and smooth flagella 1. Diatom – Surrounded by a two part glass like wall and are a major component of phytoplankton.Phytoplankton account for half of the photosynthetic activity on earth – responsible for much of the oxygen in our atmosphere.
33 2. Golden Algae – Have two flagella and their color results from carotenoids.
35 28.6 Threadlike pseudopodia Pseudopodia extend and help to injest microorganisms.
36 28.7 ~ Amoebozoans Lobed shaped pseudopodia *Entamoebas – parasites of vertebrates and cause amebic dysentry in humans.*Slime molds – extend their pseudopodia through decomposing material, engulfing food by phagocytosis.
37 28.8 ~ Red & Green Algae are the closest relatives of land plants.
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