Chapter 3Chapter 3

Functional Anatomy of Prokaryotic Functional Anatomy of Prokaryotic and Eukaryotic Cellsand Eukaryotic Cells

Prokaryotes can be grouped based on morphology Genetically determined

Monomorphic vs pleomorphic

Size Range 0.2 to 80 um in diameter2 to 600 um in lengthAverage size: 0.2 -1.0 µm × 2 - 8 µm

Morphology of Prokaryotic CellsMorphology of Prokaryotic Cells

Prokaryotes exhibit a Prokaryotes exhibit a variety of shapesvariety of shapes

Most common Most common

SpiralSpiral

Uncommon ShapesUncommon Shapes

Stella

Haloarcula

Cells may form groupingsCells may form groupingsCells adhere together after division Cells adhere together after division Form characteristic arrangementsForm characteristic arrangements

Depends on plan of divisionDepends on plan of division

NeisseriaNeisseria

EEnterococcusnterococcus

MicrococcusMicrococcus

Sarcina Sarcina

Staphylococcus aureusStaphylococcus aureus

Bacillus anthracis Bacillus anthracis

Bacillus megateriumBacillus megaterium

Bordetella pertussisBordetella pertussis

Layers External to Cell WallLayers External to Cell Wall

GlycocalyxGlycocalyxMade inside the cell; excreted to surfaceMade inside the cell; excreted to surfaceGeneral functionsGeneral functions

ProtectionProtectionAttachmentAttachmentMotility Motility

Capsule or Slime LayerCapsule or Slime Layer Chemical composition varies Chemical composition varies

depending on speciesdepending on species

FlagellaFlagella Naked filaments composed of flagellin Naked filaments composed of flagellin Rotate clockwise/counterclockwise Rotate clockwise/counterclockwise

Runs and tumblesRuns and tumblesTaxisTaxis

Flagella structure has Flagella structure has three basic partsthree basic parts

FilamentFilament

HookHook

Basal bodyBasal body

Polar - MonotrichousPolar - Monotrichous

PeritrichousPeritrichous

Polar -LophotrichousPolar -Lophotrichous

Polar -amphitrichousPolar -amphitrichous

Axial filamentsAxial filaments

Bundles of endoflagella that spiral around cellBundles of endoflagella that spiral around cell

Spirochete bacteria onlySpirochete bacteria only

Corkscrew motion Corkscrew motion

Attachment ProteinsAttachment Proteins Fimbriae - bacteriaFimbriae - bacteria

Filaments of pilin proteinFilaments of pilin protein Attachment Attachment

Hami – archaeaHami – archaea Hooked protein filamentHooked protein filament AttachmentAttachment

Sex PiliSex Pili Pilin tubules Pilin tubules Exchange of DNA Exchange of DNA

• Cannulae – thermophilic archaea Cannulae – thermophilic archaea • Spinae - marine bacteria Spinae - marine bacteria

• Connect cells over distancesConnect cells over distances• Creates mesh-like network Creates mesh-like network

Prokaryotic Prokaryotic Cell WallCell Wall

Determines shape of cellDetermines shape of cellProtects from osmotic pressure Protects from osmotic pressure Anchor point for flagella Anchor point for flagella Contributes to virulence Contributes to virulence

Unique chemical structureUnique chemical structureBacteria vs. ArchaeaBacteria vs. ArchaeaGram positive vs. Gram-negativeGram positive vs. Gram-negative

Peptidoglycan (PTG) (murein)Peptidoglycan (PTG) (murein)Sugar found only in bacteria Sugar found only in bacteria Archaea may have proteins or alternate sugarsArchaea may have proteins or alternate sugars

Basic structure of PTGBasic structure of PTG

Disaccharide polymer Disaccharide polymer N-acetylglucosamin (NAG)N-acetylglucosamin (NAG) N-acetylmuramic acid (NAM)N-acetylmuramic acid (NAM)

Glycan chain held together by Glycan chain held together by amino acidsamino acids

Tetrapeptide chainTetrapeptide chain

Protein crossbridges may or may Protein crossbridges may or may not be present not be present

Mostly G+Mostly G+

Gram positive cell wallGram positive cell wall Thick layer of PTGThick layer of PTG

Teichoic acidsTeichoic acids Lipoteichoic or Wall Lipoteichoic or Wall

teichoic acidsteichoic acids Polyalcohols that provide Polyalcohols that provide

antigenic specificityantigenic specificity

May have external May have external protein or sugar layerprotein or sugar layer

Gram-negative cell wallGram-negative cell wall

Little or no PTGLittle or no PTG

Outer lipopolysaccharide Outer lipopolysaccharide membrane (LPS)membrane (LPS)

O-specific polysaccharide O-specific polysaccharide side chainside chain

Lipid A endotoxin Lipid A endotoxin

Significant periplasmic Significant periplasmic spacespace

GRAM STAININGGRAM STAINING Gram-positive and gram-negative bacteria can be Gram-positive and gram-negative bacteria can be

identified using a “gram stain”identified using a “gram stain”

Summary of Gram + vs. Gram – Summary of Gram + vs. Gram –

G+ cell G+ cell many rigid layers of peptidoglycanmany rigid layers of peptidoglycan teichoic acidsteichoic acids No outer LPS membrane No outer LPS membrane 2 ring basal body anchoring flagella2 ring basal body anchoring flagella

G- cell G- cell Little or no peptidoglycanLittle or no peptidoglycan no teichoic acidsno teichoic acids LPS outer membraneLPS outer membrane 4 ring basal body anchoring flagella4 ring basal body anchoring flagella

Atypical cell wallAtypical cell wall Acid-fast cell wallsAcid-fast cell walls

Classified as gram-positiveClassified as gram-positive mycolic acidmycolic acid bound to PTG bound to PTG MycobacteriumMycobacterium NocardiaNocardia

ChlamydiaChlamydia Classified as Gram – with Classified as Gram – with

no PTGno PTG cysteine-rich proteins cysteine-rich proteins

No cell wall No cell wall MycoplasmasMycoplasmasSterols in plasma membraneSterols in plasma membrane

Structures Structures InternalInternal to Cell Wall to Cell Wall

Cytoplasmic membraneCytoplasmic membraneDelicate thin fluid structureDelicate thin fluid structureDefines boundaryDefines boundaryServes as a semi permeable barrierServes as a semi permeable barrier

Fluid mosaic modelFluid mosaic model

Phospholipid BilayerPhospholipid BilayerAmphipathic Amphipathic

Embedded with numerous proteinsEmbedded with numerous proteins receptors , transport, enzymes receptors , transport, enzymes

Prokaryotes typicallydon’t have membrane sterols Prokaryotes typicallydon’t have membrane sterols Bacteria may have hopanoids Bacteria may have hopanoids

Photosynthetic pigments on in-foldingsPhotosynthetic pigments on in-foldings chromatophoreschromatophores or or thylakoidsthylakoids

Archaea have distinct membrane lipidsArchaea have distinct membrane lipidsEther linkageEther linkage

Diether or tetraetherDiether or tetraether

Glycerol group enantiomer Glycerol group enantiomer Branched isoprenoid sidechainBranched isoprenoid sidechain MayMay form mono-layer with greater rigidity form mono-layer with greater rigidity

Top: archaeal phospholipid, 1 isoprene sidechain, 2 ether linkage, 3 L-glycerol, 4 phosphate groupMiddle:bacterial and eukaryotic phospholipid: 5 fatty acid, 6 ester linkage, 7 D-glycerol, 8 phosphate groupBottom: 9 lipid bilayer of bacteria and eukaryotes, 10 lipid monolayer of some archaea.

Membrane is selectively permeableMembrane is selectively permeableFew molecules pass through freelyFew molecules pass through freelyMovement involves both active and passive Movement involves both active and passive

processesprocesses

passive processes passive processes no energy (ATP) required no energy (ATP) required Along gradient Along gradient simple diffusion, facilitated diffusion, osmosissimple diffusion, facilitated diffusion, osmosis

Simple diffusion Simple diffusion

Facilitated diffusionFacilitated diffusion

OsmosisOsmosis Osmotic pressure Osmotic pressure

active processesactive processesenergy (ATP) requiredenergy (ATP) required

Active transportActive transport

Group translocationGroup translocation Phosphotransferase systemPhosphotransferase system PEP group translocationPEP group translocation

PEP transferase animation

Internal StructuresInternal Structures

Structures essential for lifeStructures essential for life ChromosomeChromosome RibosomeRibosome

Optional but may provide selective advantageOptional but may provide selective advantage CytoskeletonCytoskeleton PlasmidPlasmid Storage granulesStorage granules Endospores Endospores

Internal StructuresInternal Structures

Primary ChromosomePrimary Chromosome Resides in nucleoid Resides in nucleoid Typically single circular Typically single circular

chromosomechromosome Archaea - histone proteinsArchaea - histone proteins Bacteria - condensin protiensBacteria - condensin protiens Asexual reproductionAsexual reproduction

Binary fission, budding, fragmenting, Binary fission, budding, fragmenting, sporesspores

PlasmidsPlasmidsSmall DNA moleculesSmall DNA moleculesreplicated independentlyreplicated independentlynonessential information nonessential information used in genetic engineering biotechnologyused in genetic engineering biotechnology

Ribosomes (70S)Ribosomes (70S) Composed of large and small subunitsComposed of large and small subunits

made of riboprotein and ribosomal RNAmade of riboprotein and ribosomal RNA differ in density from eukaryotic ribosomesdiffer in density from eukaryotic ribosomes

• InclusionsInclusions Metachromatic granules Metachromatic granules Polysaccharide granulesPolysaccharide granules lipid inclusionslipid inclusions sulfur granulessulfur granules carboxyzomes carboxyzomes magnetosomesmagnetosomes Gas vesiclesGas vesicles

EndosporesEndospores ““Resting cells”Resting cells”

Highly resistantHighly resistantHeat, desiccation, Heat, desiccation,

chemicals and UV lightchemicals and UV light

Not reproduction!Not reproduction!

Endospore producers include Clostridium and Bacillus