Prokaryotes and

Eukaryotes

Classification of OrganismsHaeckel (1894)Three

kingdoms

Whittaker (1959)Five

kingdoms

Woese (1977)Six kingdoms

Woese (1990)Three

domains

ProtistaMonera

Eubacteria Bacteria

Archaebacteria Archaea

Protista Protista

EukaryaPlantaeFungi Fungi

Plantae Plantae

Animalia Animalia Animalia

Major DifferenceCHARACTERISTICS PROKARYOTES EUKARYOTESNucleus Non-membrane

boundMembrane bound

DNA single multipleChromosome Circular LinearHistones -/+ +Organelles - +Cell wall Peptidoglycan -/ cellulose/ chitinReproduction Binary fission Asexual/ sexualRibosomes 70s 80sETS Cell membrane mitochondria

Bacteria

Bacteria are prokaryotic cells, the simplest of microbial cells. They consist of cell portoplasm contained within a retaining a structure or cell envelope.

prokaryotic simple, single-celled organisms distinct cell wals containing peptidoglycan

layerNo true nucleus (only nucleoid) free-floating DNA (some w/ plasmid)

MORPHOLOGY

Prokaryotes exhibit a variety of shapes

– Most common

• Coccus– Spherical

• Bacillus– Rod or cylinder

shaped

MORPHOLOGY

Prokaryotes exhibit a variety of shapes

– Other shapes• Coccobacillus

– Short round rod• Vibrio

– Curved rod• Spirillum

– Spiral shaped• Spirochete

– Helical shape• Pleomorphic

– Bacteria able to vary shape

MORPHOLOGY

Division along a single plane may result in pairs or chains of cells

– Pairs = diplococci• Example: Neisseria

gonorrhoeae

– Chains = streptococci

• Example: species of Streptococcus

Arrangement:

MORPHOLOGY

Division along several random planes form clusters

– Example: species of Staphylococcus

Arrangement:

Division along two or three perpendicular planes form cubical packets

– Example: Sarcina genus

General Structure

General Structure of a Prokaryotic Cell

CELL APPENDAGES

FLAGELLA

• Some bacteria have protein appendages– Not essential for life

• Aid in survival in certain environments

– They include• Flagella• Pili

FLAGELLA

Flagella– Long protein structure– Responsible for motility

• Use propeller like movements to push bacteria

• Can rotate more than 100,00 revolutions/minute

– 82 mile/hour

– Some important in bacterial pathogenesis

• H antigen useful in distinguishing among serovras of gram negative bacteria

FLAGELLAFlagella structure has three basic parts

– Filament• Extends to exterior• Made of proteins called

flagellin

– Hook• Curved sheath• Connects filament to cell

– Basal body• Anchors flagellum into

cell wall and membrane

Figure 4.8b

FLAGELLAR ARRANGEMENTS

1. Monotrichous – single flagellum at one end2. Lophotrichous – small bunches arising from one end

of cell3. Amphitrichous – flagella at both ends of cell4. Peritrichous – flagella dispersed over surface of cell,

slowest

FLAGELLAR ARRANGEMENTS

FLAGELLA

Motile Cells

Axial Filaments

• Endoflagella• In spirochetes• Anchored at one end

of a cell• Rotation causes cell

to move

PILI

• Rigid tubular structure made of pilin protein

•Found only in Gram negative cells

•Functions – Sexual pili—joins bacterial cells for DNA

transfer (conjugation)– Common pili—adhesion

FIMBRAE

•Fine hairlike bristles from the cell surface

•Function in adhesion to other cells and surfaces

CELL ENVELOPE

GLYCOCALYX• Coating of molecules external to the cell wall,

made of sugars and/or proteins• 2 types

1. slime layer - loosely organized and attached2. capsule – highly organized, tightly attached

• Functions– attachment– inhibits killing by white blood cells– receptor

BIOFILM

Dental Plaque A polysaccharide-encased

mass of bacteria coating the surface of a tooth

Streptococcus mutans uses sucrose to synthesize a biofilm

Other bacteria can then adhere to the layer

(a) The appearance of colonies composed of encapsulated cells (mucoid) compared with those lacking capsules (nonmucoid).

(b) Staining reveals the microscopic appearance of a large, well- developed capsule.

CELL WALL

• Bacterial cell wall – Rigid structure– Surrounds cytoplasmic membrane– Determines shape of bacteria– Holds cell together– Prevents cell from bursting– Unique chemical structure

• Distinguishes Gram positive from Gram-negative

GRAM POSITIVE GRAM NEGATIVE

GRAM POSITIVE WALL

•Rigidity of cell wall is due to peptidoglycan (PTG)

– Compound found only in bacteria

•Basic structure of peptidoglycan

– Alternating series of two subunits• N-acetylglucosamine (NAG)• N-acetylmuramic acid (NAM)

– Joined subunits form glycan chain• Glycan chains held together by

string of four amino acids– Tetrapeptide chain

GRAM POSITIVE WALL– Relatively thick layer of peptidoglycan

• As many as 30– Regardless of thickness, peptidoglycan is permeable to

numerous substances

– Teichoic acid component of peptidoglycan; composed of glycerol and phosphate

– Lipoteucholic acid is attached to the lipids of cytoplasmic membrane

• Gives cell negative charge

GRAM POSITIVE WALL

GRAM POSITIVE GRAM NEGATIVE

GRAM NEGATIVE WALL

– More complex than Gram+– Only contains thin layer of

peptidoglycan• Peptidoglycan sandwiched

between outer membrane and cytoplasmic membrane

• Region between outer membrane and cytoplasmic membrane is called periplasm or periplasmic space

– Gel-like area– Most secreted proteins

contained here

GRAM NEGATIVE WALL

• Outer membrane Connected to the peptidoglycan layer by lipoproteins Constructed of lipid bilayer

• Much like cytoplasmic membrane but outer layer made of lipopolysaccharides and phospholipids

• Outer membrane also called the lipopolysaccharide layer or LPS layer

– LPS severs as barrier to a large number of molecules• Small molecules or ions pass through channels called

porins• Specific channel proteins are present

GRAM NEGATIVE WALL

•O-specific polysaccharide chain– Directed away from membrane

• Opposite location of Lipid A– Used to identify certain species or strains

• E. coli O157:H7 refers to specific O-side chain

•Lipid A– Portion that anchors LPS molecule in lipid bilayer– Plays role in recognition of infection

• Molecule present with Gram negative infection of bloodstream--endotoxin

GRAM NEGATIVE WALL

Gram-Positive Membrane

Gram-Negative Outer Membrane

CELL WALL• Peptidoglycan layer as a target

– Many antimicrobial interfere with the synthesis of peptidoglycans or alter its structural integrity

– Examples include• Penicillin• Lysozyme

• Penicillin– Binds proteins involved in cell wall synthesis

• Prevents cross-linking of glycan chains by tetrapeptides

– More effective against Gram positive bacterium• Due to increased concentration of peptidoglycans• Penicillin derivatives produced to protect against Gram negatives

CELL WALL

• Lysozymes– Produced in many body fluids including tears and

saliva– Breaks bond linking NAG and NAM

• Destroys structural integrity of cell wall

– Enzyme often used in laboratory to remove peptidoglycan layer from bacteria

• Produces protoplast in G+ bacteria• Produces spheroplast in G- bacteria

CELL WALL

• Differences in cell wall account for• differences in staining• Characteristics:

– Gram-positive bacterium retain crystal violet-iodine complex of Gram stain

– Gram-negative bacterium lose crystal violet-iodine complex

The Gram Stain

CELL WALL

• Some bacterium naturally lack cell wall– Mycoplasma

• Bacterium causes mild pneumonia• Have no cell wall

–Antimicrobial directed towards cell wall ineffective

• Sterols in membrane account for strength of membrane

CYTOPLASMIC MEMBRANE

• Cell (Cytoplasmic) membrane– Delicate thin fluid structure– Surrounds cytoplasm of cell– Defines boundary– Serves as a semi permeable barrier

• Barrier between cell and external environment

CELL MEMBRANE

•Structure is a lipid bilayer with embedded proteins

– Bilayer consists of two opposing layers

• Layer composed of phospholipids

– Each contains a hydrophilic phosphate head and hydrophobic fatty acid tail

CELL MEMBRANE

•Membrane is embedded with numerous protein

– More that 200 different proteins– Proteins function as receptors,

channels proteins, and transport proteins

– Provides mechanism to sense surroundings

– Proteins are not stationary• Constantly changing position

– Called fluid mosaic model

CYTOPLASM

CYTOPLASM

• Dense gelatinous solution of sugars,• amino acids, & salts

• 70-80% water

• Serves as solvent for materials• used in all cell functions

STRUCTURES WITHIN CYTOPLASM

• Bacterial cells have variety of internal structures• Some structures are essential for life

– Chromosome– Ribosome

• Others are optional and can confer selective advantage– Plasmid– Storage granules– Endospores

INTERNAL STRUCTURES

Chromosome– Resides in cytoplasm

• In nucleoid space– Typically single chromosome: protein and DNA– Circular double-stranded molecule– Contains all genetic information

Plasmid– Circular DNA molecule

• Generally 0.1% to 10% size of chromosome– Extrachromosomal

• Independently replicating– Encode characteristic

• Potentially enhances survival– Antimicrobial resistance– Tolerance to toxic metals

INTERNAL STRUCTURE

Ribosome– Involved in protein synthesis– Composed of large and small

subunits• Units made of protein 40%

and ribosomal RNA 60%– Prokaryotic ribosomal subunits

• Large = 30S• Small = 50S

– Small than eukaryotic ribosomes

• Difference often used as target for antimicrobials

INTERNAL STRUCTURES

Storage granules– Accumulation of polymers

• Synthesized from excess nutrient– Example = glycogen

» Excess glucose in cell is stored in glycogen granules

Gas vesicles– Small protein compartments

• Provides buoyancy to cell• Regulating vesicles allows

organisms to reach ideal position in environment

INTERNAL STRUCTURES

Endospores– Dormant cell types

• Produced through sporulation• Theoretically remain dormant for

100 years– Resistant to damaging conditions

• Heat, desiccation, chemicals and UV light

– Vegetative cell produced through germination

• Germination occurs after exposure to heat or chemicals

• Germination not a source of reproduction

Common bacteria genus that produce endospores include Clostridium and Bacillus

Inclusions• Metachromatic granules

(volutin)• Polysaccharide granules• Lipid inclusions• Sulfur granules• Carboxysomes

• Gas vacuoles• Magnetosomes

• Phosphate reserves

• Energy reserves• Energy reserves• Energy reserves• Ribulose 1,5-diphosphate

carboxylase for CO2 fixation• Protein covered cylinders• Iron oxide

(destroys H2O2)

Inclusions

Archaea

• primitive prokaryotes• extermophiles• lacks peptidoglycan in their cell wall• ether-linked membrane lipids

Phylogenetic Tree of Archaea

Archaea Morphology

Basic Archaeal Shapes : At far left, Methanococcus janaschii, a coccus form with numerous flagella attached to one side. At left center, Methanosarcina barkeri, a lobed coccus form lacking flagella. At right center, Methanothermus fervidus, a short bacillus form without flagella. At far right, Methanobacterium thermoautotrophicum, an elongate bacillus form.

Archaea Morphology

• Membrane lipids– ether bonds link glycerol to hydrocarbon side

chains– lacks fatty acids– side chains composed of repeating isoprene units– major lipid components: glycerol diether and

diglycerol teraether– lipid monolayer

Archaea Morphology

Archaea Morphology

• Cell Wall– lacks outer membrane– pseudomurein:

• N-acetylglucosamine + N –acetyltalosaminuronic acid• β-1,3 glycosidic linkage• L-amino acids

– Polysaccharide cell walls• Methanosarcina: glucose, glucuronic acid, uronic acid

galactosamine, and acetate• Halococcus: same as Methanosarcina cell wall + Sulfate

ions

Archaea Morphology

• Cell Wall– S-layers: paracrystalline surface layers

• proteins or glycoprotein arranged in various symmetries

• Functions:– structural support– interface btwn cell and its environment– selective sieve– retain proteins near cell surface

Archaea Morphology

• Other Cell Walls– Natronococcus: haloalkalophilic species of

Archaea• glycoprotein cell wall contains L-glutamate as a single

type of amino acid linking glucose and glucose derivatives

Archaea

• Crenarchaeaota: most thermophilic archaea are found in this group. They use sulfur compounds as electron donors or as acceptors. Not all are thermophilic.

• Euryarcheota: methanogens, halophiles, thermophiles.

• Korarcheota; found in hot springs. None have been grown in pure culture.

The hot springs of Yellowstone National Park, USA, were among the first places Archaea were discovered. At left is Octopus Spring, and at right is Obsidian Pool. Each pool has slightly different mineral content, temperature, salinity, etc., so different pools may contain different communities of archaeans and other microbes. The biologists pictured above are immersing microscope slides in the boiling pool onto which some archaeans might be captured for study.

Salt-lovers : immense bloom of a halophilic ("salt-loving") archaean species at a salt works near San Quentin, Baja California Norte, Mexico. This archaean, Halobacterium, also lives in enormous numbers in salt ponds at the south end of San Francisco Bay; interested residents of this area should take the Dumbarton Bridge for the best views.

Figure 4.22a

Eukarya

Flagella and Cilia

Figure 4.23a–b

Figure 4.23c

• Microtubules • Tubulin• Nine pairs + two arrangements

Cell Wall

• Cell wall– Plants, algae, fungi– Carbohydrates

• Cellulose, chitin, glucan, mannan• Glycocalyx

– Carbohydrates extending from animal plasma membrane

– Bonded to proteins and lipids in membrane

Plasma Membrane

• Phospholipid bilayer• Peripheral proteins• Integral proteins• Transmembrane proteins• Sterols• Glycocalyx carbohydrates

Plasma Membrane• Selective permeability allows passage of some

molecules• Simple diffusion• Facilitative diffusion• Osmosis• Active transport• Endocytosis

– Phagocytosis: Pseudopods extend and engulf particles.– Pinocytosis: Membrane folds inward bringing in fluid and

dissolved substances.

Eukaryotic Cell• Cytoplasm membrane:Substance inside plasma

and outside nucleus• Cytosol: Fluid portion of cytoplasm• Cytoskeleton: Microfilaments, intermediate

filaments, microtubules• Cytoplasmic streaming: Movement of cytoplasm

throughout cells

Organelles• Membrane-bound

– Nucleus: Contains chromosomes– ER: Transport network– Golgi complex: Membrane formation and secretion– Lysosome: Digestive enzymes– Vacuole: Brings food into cells and provides support– Mitochondrion: Cellular respiration– Chloroplast: Photosynthesis– Peroxisome: Oxidation of fatty acids; destroys H2O2

Eukaryotic Cell

• Not membrane-bound– Ribosome: Protein synthesis– Centrosome: Consists of protein fibers and

centrioles– Centriole: Mitotic spindle formation

Nucleus

Figure 4.24

Endoplasmic Reticulum

Figure 4.25

Ribosomes

• 80S– Membrane-bound Attached to ER– Free In cytoplasm

• 70S– In chloroplasts and mitochondria

Golgi Complex

Figure 4.26

Lysosomes and Vacuoles

Figure 4.22b

Mitochondrion

Figure 4.27

Chloroplast

Figure 4.28

Figures 10.2, 10.3

Endosymbiotic Theory

Endosymbiotic Theory

UN 4.1

Comparison of the Three DomainsCHARACTERISTICS BACTERIA ARCHAEA EUKARYA

Cell Nucleus - - +Chromosome Single, circular Single, circular Multiple, linearHistone Proteins - + +Peptidoglycan Cell Wall + - -

Membrane lipids Ester-linked Ether-linked Ester-linkedRibosome sedimentation rate

70s 70s 80s

Ribosome susceptibility to diptheria toxin

- + +

1st amino acid in protein

Formylmethionine Methioine ,ethionine

Chlorophyll based photosynthesis

+ (cyannobacteria) - + (algae)

Growth above 80 OC + + -Growth above 100 OC - + -