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MicrobiologyWith Diseases by Taxonomy
Second Edition
PowerPoint® Lecture Slides
PART A
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3Cell Structure and Function
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CHAPTER 3
MicrobiologyCell structures and functionsGrowthReproductionResponsivenessMetabolismTable 3-1
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Processes of Life
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Prokaryotes
Do not have membrane surrounding their DNA; no nucleusLack various internal structures bound with phospholipid membranesSmall; ~1.0 µm in diameterSimple structureComprised of bacteria and archaea
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Eukaryotes
Have membrane surrounding DNA; have nucleusHave internal membrane-bound organellesAre larger; 10-100 µm in diameterHave more complex structureComprised of algae, protozoa, fungi, animals, and plants
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Cocci
Neisseria gonorrhea Gram negative
S. pneumoniae Gram positiveS. pyogenes
S. aureus Gram positive
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bacilli (rods)
Escherichia coli Gram negative
Bacillus cereus Gram positiveB. anthracis
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Spiral
Vibrio cholerae Gram negative
Treponema pallidum G –syphilis
Borrelia burgdorferii G-Lyme Disease
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Axial filament
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External Structures of Prokaryotic Cells
GlycocalycesFlagellaFimbriae and pili
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Glycocalyces
Gelatinous, sticky substance surrounding the outside of the cellComposed of polysaccharides, polypeptides, or bothTwo types
CapsuleSlime layer
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Capsule
Composed of organized repeating units of organic chemicalsFirmly attached to cell surfaceProtects cells from drying outMay prevent bacteria from being recognized and destroyed by host
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Slime Layer
Loosely attached to cell surfaceWater solubleProtects cells from drying outSticky layer that allows prokaryotes to attach to surfaces
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Flagella
Are responsible for movementHave long structures that extend beyond cell surfaceNot all prokaryotes have flagellaSerotypes: E. coli O157:H7
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Flagellar Arrangements
Peritrichous Single polar
Tufted polar
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Axial filament
Treponemapallidum
Borreliaburgdorferi
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Bacterial Movement
Figure 3.8
PLAYAnimation:Bacterial Motility
Chemotaxis/phototaxis
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Motility http://www.cellsalive.com
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Fimbriae and Pili
Nonmotile extensionsFimbriae
Sticky, proteinaceous, bristlelike projectionsUsed by bacteria to adhere to one another, to hosts, and to substances in environmentMay be hundreds per cell and are shorter than flagellaImportant function in biofilms
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Pili
Long hollow tubules composed of pilinLonger than fimbriae but shorter than flagellaBacteria typically only have one or two per cellJoin two bacterial cells and mediate the transfer of DNA from one cell to another (conjugation)Also known as conjugation pili or sex pili
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Prokaryotic Cell Wall
Provides structure and shape and protects cell from osmotic forcesAssists some cells in attaching to other cells or in eluding antimicrobial drugsAnimal cells do not have; can target cell wall of bacteria with antibiotics
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Prokaryote cell wall
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Bacterial Cell Wall
Most have cell wall composed of peptidoglycan; a few lack a cell wall entirelyPeptidoglycan composed of sugars, NAG, and NAMtetrapeptide bridges
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Cell walls
G- G +-http://www.ppws.vt.edu/~sforza/prokarote/cell_walls.html
G- G+
Scientists describe two basic types of bacterial cell walls: gram-positive and gram-negative
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G+ cell wall
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Gram-Positive Cell Wall
Relatively thick layer of peptidoglycanteichoic acidsRetains crystal violet dye in Gram staining procedure; appear purple
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Gram-Negative Cell Walls
Have only a thin layer of peptidoglycanBilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS) May be impediment to the treatment of diseaseFollowing Gram staining procedure, cells appear pink
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E. coli O157:H7
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LPS and periplasm
LPS; lipopolysaccharide (union of lipid with sugar)Also known as endotoxinLipid portion known as lipid A
Dead cells release lipid A when cell wall disintegratesMay trigger fever, vasodilation, inflammation, shock, and blood clottingCan be released when antimicrobial drugs kill bacteria
Periplasm located between outer membrane and cell membrane
Contains peptidoglycan and periplasmContains water, nutrients, and substances secreted by the cell, such as digestive enzymes and proteins involved in transport
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Bacterial Cell Walls
Figure 3.13b
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Cell walls
G- G +-http://www.ppws.vt.edu/~sforza/prokarote/cell_walls.html
G- G+
Scientists describe two basic types of bacterial cell walls: gram-positive and gram-negative
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Archael Cell Walls
Do not have peptidoglycanCell walls contain variety of specialized polysaccharides and proteinsGram-positive archaea stain purple Gram-negative archaea stain pink
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Phospholipid Bilayer of CytoplasmicMembrane
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Prokaryotic Cytoplasmic Membrane
Referred to as phospholipid bilayer; composed of lipids and associated proteinsApproximately half the membrane is composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels
Integral proteins Peripheral proteins Glycoproteins
Fluid mosaic model describes current understanding of membrane structure
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Control of Substances Across CytoplasmicMembrane
Naturally impermeable to most substancesProteins allow substances to cross membraneOccurs by passive or active processesMaintains a concentration gradient and electrical gradient
Chemicals concentrated on one side of the membrane or the otherVoltage exists across the membrane
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Passive Processes of Transport
DiffusionFacilitated diffusion Osmosis
Isotonic solution Hypertonic solution Hypotonic solution
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Effects of Solutions on Organisms
Figure 3.18 Copyright © 2007 Pearson Education, Inc. publishing as Benjamin Cummings
Cell wall disruption
G+; lysozyme (or penicillin): protoplastG-; lysozyme; spheroplasthttp://www.cellsalive.com
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Penicillin discovered
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Penicillin Effects
http://http://www.cellsalive.comwww.cellsalive.com
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Active Processes of Transport
Active TransportUtilizes permease proteins and expends ATP
Group TranslocationSubstance chemically modified during transport
PLAYAnimation:Membrane Transport
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Nuclear region
One circular chromosome: nucleod
Plasmid: small circular DNA outside of chromosome
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Ribosome
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Inclusions
Reserve depositsVolutin (Polyphosphates): CorynebacteriumdiphtheriaSulfur granules: ThiobacillusCarboxysomes (enzyme for photosynthesis): Cyanobacteria
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Cytoplasm of Prokaryotes
Cytosol – liquid portion of cytoplasmInclusions – may include reserve deposits of chemicalsRibosomes – sites of protein synthesisCytoskeleton – plays a role in forming the cell’s basic shapeSome bacterial cells produce dormant form called endospore
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Endospores
GerminationDormant form; NOT reproductive Resists heating, freezing, desiccation, chemicals and radiationGenera Bacillus and ClostridiumG+ rodsSpore stain
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Endospore
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Endospore stain
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Eukaryotic cell
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External Structure of Eukaryotic Cells
GlycocalycesNever as organized as prokaryotic capsulesHelps anchor animal cells to each otherStrengthens cell surfaceProvides protection against dehydrationFunction in cell-to-cell recognition and communication
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Eukaryotic Cell Walls
Fungi, algae, plants, and some protozoa have cell walls but no glycocalyxComposed of various polysaccharides
Cellulose found in plant cell wallsFungal cell walls composed of cellulose, chitin, and/or glucomannanAlgal cell walls composed of cellulose, proteins, agar, carrageenan, silicates, algin, calcium carbonate, or a combination of these
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Eukaryotic Cytoplasmic Membrane
All eukaryotic cells have cytoplasmic membraneIs a fluid mosaic of phospholipids and proteinsContains steroid lipids to help maintain fluidityControls movement into and out of cell
Uses diffusion, facilitated diffusion, osmosis, and active transportPerforms endocytosis; phagocytosis if solid substance and pinocytosis if liquid substanceExocytosis enables substances to be exported from cell
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Endocytosis
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Eukaryotes – outer structures and Nonmembranous Organelles
Flagella: “9 + 2” arrangement of microtubules in all flagellated eukaryotesCiliaRibosomes: Composed of 60S and 40S subunitsCytoskeletonCentrioles and centrosome
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Eukaryotic Flagella
Figure 3.27a
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Cytoplasm of Eukaryotes – Membranous Organelles
NucleusEndoplasmic reticulumGolgi bodyLysosomes, peroxisomes, vacuoles, and vesiclesMitochondriaChloroplasts
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Endosymbiotic Theory
Eukaryotes formed from union of small aerobic prokaryotes with larger anaerobic prokaryotes; smaller prokaryotes became internal parasites
Parasites lost ability to exist independently; retained portion of DNA, ribosomes, and cytoplasmicmembranesLarger cell became dependent on parasites for aerobic ATP productionAerobic prokaryotes evolved into mitochondriaSimilar scenario for origin of chloroplasts
Not universally accepted
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