tortora • funke • case microbiology 2 - 8 µm (1 x 10 · pdf filechapter 4...

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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lecture Slide Presentation prepared by Christine L. Case

MicrobiologyB.E Pruitt & Jane J. Stein

AN INTRODUCTIONEIGHTH EDITION

TORTORA • FUNKE • CASE

Chapter 4Functional Anatomy of Prokaryotic and

Eukaryotic Cells


Prokaryotic Cells

• Comparing Prokaryotic and Eukaryotic Cells• Prokaryote comes from the Greek words for

prenucleus.• Eukaryote comes from the Greek words for

true nucleus.

Learning objective: compare and contrast overall cell structure of prokaryotes and eukaryotes.


• Cell membrane• Cytoplasm• One circular

chromosome, not in a membrane

• No histones• No organelles• Peptidoglycan cell

walls• Binary fission

Prokaryote Eukaryote

• Cell membrane• Cytoplasm• Paired

chromosomes, in nuclear membrane

• Histones• Organelles• Polysaccharide cell

walls• Mitotic spindle


• Average size: 0.2 -1.0 µm × 2 - 8 µm (1 x 10-6 m)• Are unicellular and most multiply by binary fission• Basic shapes:

Learning objective: Identify the three basic shapes of bacteria.

COCCUS BACILLUS SPIRAL


• Pairs: diplococci, diplobacilli

• Clusters: staphylococci

• Chains: streptococci,streptobacilli

Arrangements


Arrangements of cocci:

Can be determined by division of planes.

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Arrangements of bacilli:


Arrangements of spiral bacteria:


Double-stranded helix formed by Bacillus subtilis.

Bacillus cells often remain attached to each other, forming extended chains.


• Unusual shapes (Prokaryotes)• Star-shaped Stella• Square Haloarcula (halophilic archaea – salt-loving)

• Most bacteria are monomorphic (single shape)• A few are pleomorphic (many shapes)

Figure 4.5


Learning objective: Describe the structure and function of the glycocalyx, flagella, axial filaments, fimbriae, and pili.

Prokaryote cell


• Outside cell wall• Usually sticky• A capsule is neatly

organized• A slime layer is

unorganized & loose glycocalyx

• Extracellular polysaccharide (EPS) allows cell to attach

• Capsules prevent phagocytosis

• Protects against dehydration or loss of nutrients.

Glycocalyx

Figure 4.6a, b

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• Long filamentous appendages of a filament, hook, and basal body

• Outside cell wall• Made of chains of

flagellin• Attached to a protein

hook• Anchored to the wall

and membrane by the basal body

Flagella

Figure 4.8


Flagella Arrangement

Figure 4.7

Four arrangements of flagella:


• Rotate flagella to run or tumble• Move toward or away from stimuli (positive and

negative taxis)• Flagella H proteins are antigens

(e.g., E. coli O157:H7)

Motile Cells


Motile Cells

Figure 4.9

A Proteus cell swarming may have 1000+ peritrichous flagella. (from all sides)


• Endoflagella• In spirochetes• Anchored at one end

of a cell• Rotation causes cell

to move

Axial Filaments (endoflagellum)

Figure 4.10a


Fimbriae and Pili

• Are short, thin appendages

• Fimbriae of this E. Coli cell allow attachment (velcro). Cell is beginning to divide.

• Pili are used to transfer DNA from one cell to another

Figure 4.11

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• Prevents osmotic lysis (protects against changes in water pressure)• Made of peptidoglycan (in bacteria = NAG+NAM+amino acids) –

penicillin interferes with production of peptidoglycan• Contributes to disease capability and site of action of some

antibiotics.

Cell Wall

Figure 4.6a, b

Learning objectives: Compare/contrast cell walls of gram-positive bacteria, gram-negative bacteria, archaea, and mycoplasmas.Differentiate between protoplast, spheroplast, and L form.


• Polymer of disaccharideN-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)

• Linked by polypeptides

Peptidoglycan (murein)

Figure 4.13a

The small arrows denote where penicillin interferes with linkage of peptidoglycan rows.

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.13b, c

Gram positive vs. gram negative cell walls


• Thick peptidoglycan• Teichoic acids

(alcohol+phosphate)• In acid-fast cells,

contains mycolic acid (waxy lipid) –allows them to be grouped into medically significant types.

Gram-positive cell walls Gram-negative cell walls

• Thin peptidoglycan (subject to mechanical breakage)

• No teichoic acids• Outer membrane:

• Evades phagocytosis• Barrier to certain anti-

biotics


• Teichoic acids:• Lipoteichoic acid links to plasma membrane• Wall teichoic acid links to peptidoglycan

• May regulate movement of cations (+ charge)• Polysaccharides provide antigenic variation

(identification)

Gram-Positive cell walls

Figure 4.13b


• Lipopolysaccharides, lipoproteins, phospholipids.• Forms the periplasm between the outer membrane and

the plasma membrane.• Protection from phagocytes, complement (30+ liver

proteins that protect host), antibiotics.• O polysaccharide antigen, e.g., E. coli O157:H7.• Lipid A is an endotoxin.• Porins (proteins) form channels through membrane to

pass other molecules

Gram-Negative Outer Membrane

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Gram-Negative Outer Membrane

Figure 4.13c


• Crystal violet-iodine (CV-I) crystals form in cell combining with peptidoglycan

• Gram-positive• Alcohol dehydrates peptidoglycan• CV-I crystals do not leave

• Gram-negative• Alcohol dissolves outer membrane and leaves holes

in peptidoglycan• CV-I washes out

Gram Stain Mechanism




• Mycoplasmas (Genus)• Lack cell walls• Sterols in plasma membrane

• Archaea• Wall-less, or• Walls of pseudomurein (lack NAM and D amino

acids, peptidoglycan)

Atypical Cell Walls


• Lysozyme digests disaccharide in peptidoglycan (gram+ cell walls destroyed, gram- damaged, resulting in spheroplast).

• Spheroplast is a wall-less Gram-NEGATIVE cell.• Penicillin inhibits peptide bridges in peptidoglycan.• Protoplast is a wall-less gram+ cell.• L forms are wall-less cells that swell into irregular

shapes (gram+ and -).• Protoplasts and spheroplasts are susceptible to

osmotic lysis.

Damage to Cell Walls

CORRECTED SLIDE

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Plasma (cytoplasmic) Membrane

Figure 4.14a

Learning objectives: Describe the structure, chemistry, and functions of prokaryotic plasma membrane.Define simple diffusion, facilitated diffusion, osmosis, active transport, and group translocation.



Plasma Membrane – Fluid Mosaic Model

• Selectively permeable• Phospholipid bilayer• Peripheral proteins• Integral proteins• Transmembrane proteins

Figure 4.14b


• Membrane is as viscous as olive oil.

• Proteins move to function• Phospholipids rotate and

move laterally

Fluid Mosaic Model

Figure 4.14b


• Carry enzymes for metabolic reactions: nutrient breakdown, energy production, photosynthesis

• Selective permeability allows passage of some molecules

• Enzymes for ATP production• Photosynthetic pigments on foldings called

chromatophores or thylakoids• Damage to the membrane by alcohols, quaternary

ammonium (detergents) and polymyxin antibiotics causes leakage of cell contents.

Plasma Membrane


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• High to low concentration:• Movement may be passive (no energy expenditure –

diffusion or facilitated diffusion):• Simple diffusion: Movement of a solute from an area

of high concentration to an area of low concentration. (ions move until equilibrium reached)

• Facilitative diffusion: Solute combines with a transporter protein in the membrane.

Movement Across Membranes



Figure 4.17


• Osmosis (always involves water):• Movement of water

across a selectively permeable membrane from an area of high water concentration to an area of lower water.

• Osmotic pressure• The pressure needed to

stop the movement of water across the membrane.


Figure 4.18a

Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 4.18c-e

Osmosis


• Low to high concentration (against gradient) – cell must expend energy:

• Active transport of substances requires a transporter protein and ATP.

• Group translocation of substances requires a transporter protein and PEP. (phospheonolpyruvic acid)



• Cytoplasm is the fluid substance inside the plasma membrane (water, inorganic and organic molecules, DNA, ribosomes, and inclusions)

Cytoplasm

Figure 4.6a, b

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• Nuclear area (nucleoid) – contains single long, continuous, double-stranded DNA called bacterial chromosome.

• Bacteria can contain plasmids – circular DNA

Nuclear Area

Figure 4.6a, b

Learning objectives: Identify functions of the nuclear area, ribosomes, and inclusions.


Ribosomes = rRNA + proteins

Figure 4.6a

Sites of protein synthesis (rRNA) – free floating, not tied to endoplasmic reticulum as in eukaryotes.


Ribosomes

Figure 4.19

The letter S refers to Svedberg units = relative rate of sedimentation.

Because of differences in prokaryotic and eukaryotic ribosomes, the microbe can be killed by antibiotics while eukaryotic host cell is unaffected.


• Metachromatic granules (volutin)

• Polysaccharide granules• Lipid inclusions• Sulfur granules• Carboxysomes

• Gas vacuoles• Magnetosomes

Inclusions

•Phosphate reserves

•Energy reserves•Energy reserves•Energy reserves•Ribulose 1,5-diphosphate carboxylase for CO2 fixation•Protein covered cylinders•Iron oxide (destroys H2O2)

FUNCTION


Iron-oxide inclusions in some gram-negative bacteria that act like magnets.

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• Resting cells formed for survival• Sporulation: Endospore formation• Resistant to desiccation, heat, chemicals• Bacillus, Clostridium• Germination: Return to vegetative state

Endospores

Learning objective: Describe the functions of endospores, sporulation, and endospore germination.


Endospores tend to form under conditions of stress.


Eukaryotic Cells

• Comparing Prokaryotic and Eukaryotic Cells• Prokaryote comes from the Greek words for

prenucleus.• Eukaryote comes from the Greek words for

true nucleus.




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Eukaryotic Flagella and Cilia

Euglena (evolutionarybuilding block)

Prokaryotic flagella rotate, eukaryotic flagella wave


Flagella and Cilia• Flagella are few and long (motility), cilia are

numerous and short (motility and move substances along cell surface)

• Microtubules • Tubulin• 9 pairs + 2 arrangements

Figure 4.23c


• Cell wall• Plants, algae, some fungi contain cellulose• Carbohydrates

• Cellulose, chitin (fungal), glucan & mannan (yeast)• Glycocalyx surround animal cells (strength, attachment

to other cells)• Carbohydrates extending from animal plasma

membrane• Bonded to proteins and lipids in membrane

Cell Wall and GlycocalyxLearning objective: Compare and contrast prokaryotic and eukaryotic cell walls and glycocalyxes.


• Phospholipid bilayer in both p. and e. cells• Peripheral proteins• Integral proteins• Transmembrane proteins• Sterols• Glycocalyx carbohydrates not found in p. cells except

Mycoplasma bacteria

Plasma Membrane

Learning objective: Compare and contrast prokaryotic and eukaryotic plasma membranes.


• Selective permeability allows passage of some molecules

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

• Phagocytosis: Pseudopods extend and engulf particles (solids)

• Pinocytosis: Membrane folds inward bringing in fluid and dissolved substances (liquids)

Plasma Membrane


• Cytoplasm Substance inside plasma membrane and outside nucleus

• Cytosol Fluid portion of cytoplasm• Cytoskeleton Microfilaments,

intermediate filaments, microtubules

• Cytoplasmic streaming Movement of cytoplasm throughout cells

Eukaryotic Cell

Learning objectives:

Define organelle.

Describe the functions of the nucleus, endoplasmic reticulum, ribosomes, Golgi complex, lysosomes, vacuoles, mitochondria, chloroplasts, peroxisomes, and centrosomes.

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• Specialized membrane-bound structure in cytoplasm:• Nucleus Contains chromosomes (DNA)• ER Transport network, ribosomes• Golgi complex Membrane formation and protein

secretion• Lysosome Digestive enzymes• Vacuole Brings food into cells and

provides support• Mitochondrion Cellular respiration (ATP)• Chloroplast Photosynthesis (70S ribosomes)• Peroxisome Oxidation of fatty acids;

destroys H2O2

Organelles


• Not membrane-bound:• Ribosome Protein synthesis (translation)• Centrosome Consists of protein fibers and

centrioles• Centriole Mitotic spindle formation

Eukaryotic Cell


Eukaryotic Nucleus

Figure 4.24


Endoplasmic Reticulum

Figure 4.25

Rough ER contains ribosomes – site of protein translation

Smooth ER performs various functions:•Synthesizes phospholipids, fats, steroids•In liver: glucose release and detoxify toxins•Creates vesicles


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

• 70S• In chloroplasts and mitochondria

Ribosomes


Golgi Complex

Figure 4.26

Golgi complex modifies, sorts, and packages proteins received from the ER; discharges proteins via exocytosis; replaces portions of the plasma membrane; and forms lysosomes (digestive enzymes).

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Lysosomes (digestive enzymes)

Figure 4.22b


Vacuoles (storage of toxins, food, water)

Figure 4.22b


Mitochondrion (furnace of the cell)

Figure 4.27

Site of the Krebs Cycle, which produces the energy currency of the cell - ATP


Chloroplast

Figure 4.28

Structure similar to mitochondria – the reverse side of respiration:C6H12O6 + O2 = H2O + CO2 + ATP

Photosynthesis:H2O + CO2 + sun = C6H12O6 + O2


Endosymbiotic Theory

Figure 10.2

Learning objective: Discuss evidence that supports the endosymbiotic theory of eukaryotic evolution.

•Mitochondria and chloroplasts resemble bacteria in size and shape as do their ribosomes•These organelles contain circular DNA like prokaryotes and can reproduce apart from their host cell

tortora • funke • case microbiology 2 - 8 µm (1 x 10 · pdf filechapter 4...

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