BACTERIAL MORPHOLOGY: PROCARYOTIC AND EUCARYOTIC CELLS Chapter 4

BACTERIAL MORPHOLOGY:BACTERIAL MORPHOLOGY:PROCARYOTIC AND PROCARYOTIC AND EUCARYOTIC CELLSEUCARYOTIC CELLS

Chapter 4Chapter 4

Eucaryotic cellsEucaryotic cells

•any organism with a fundamental any organism with a fundamental cell type containing cell type containing membrane-membrane-enclosed organellesenclosed organelles

Prokaryotic CellsProkaryotic Cells•Comparing Prokaryotic and Comparing Prokaryotic and

Eukaryotic CellsEukaryotic Cells– Prokaryote comes from the Prokaryote comes from the

Greek words for prenucleus.Greek words for prenucleus.– Eukaryote comes from the Eukaryote comes from the

Greek words for true Greek words for true nucleus.nucleus.

• One circular One circular chromosome, chromosome, not in a not in a membranemembrane

• No histonesNo histones

• No organellesNo organelles

• Peptidoglycan Peptidoglycan cell wallscell walls

• Binary fissionBinary fission

ProkaryoteProkaryote EukaryoteEukaryote• Paired Paired

chromosomes, in chromosomes, in nuclear nuclear membranemembrane

• HistonesHistones

• OrganellesOrganelles

• Polysaccharide Polysaccharide cell wallscell walls

• Mitotic spindleMitotic spindle

• Average size: 0.2 -1.0 µm Average size: 0.2 -1.0 µm 2 - 8 µm 2 - 8 µm

• Basic shapes:Basic shapes:

Procaryotes (Bacteria)

Protozoan (eucaryote)

Procaryotic cellsProcaryotic cells

•any organism with a any organism with a fundamental cell type fundamental cell type without without nucleusnucleus

•Unusual shapesUnusual shapes– Star-shaped Star-shaped StellaStella– Square Square HaloarculaHaloarcula

•Most bacteria are monomorphicMost bacteria are monomorphic

•A few are pleomorphicA few are pleomorphic

Figure 4.5

Bacteria (procaryote)

Procaryotic cells (Procaryotic cells (contcont.).)•Bacteria Bacteria

–Differentiation by:Differentiation by:

•Morphology, composition, Morphology, composition, nutritional requirements, nutritional requirements, and biochemical activities and biochemical activities and source of energyand source of energy

Shapes of bacteriaShapes of bacteria

• coccus (spheres)coccus (spheres)

• bacillus (rods)bacillus (rods)

• spiral (twisted)spiral (twisted)

• pleomorphic (several)pleomorphic (several)

• Pairs: diplococci, Pairs: diplococci, diplobacillidiplobacilli

• Clusters: Clusters: staphylococcistaphylococci

• Chains: Chains: streptococci, streptococci, streptobacillistreptobacilli

ArrangementsArrangements

Arrangements of cocciArrangements of cocci

•Divide in:Divide in:–one plane=diplococcione plane=diplococci–two planes=tetradstwo planes=tetrads–three planes=sarcineaethree planes=sarcineae–multiple=staphylococcimultiple=staphylococci

Structures external to the Structures external to the bacterial cell wallbacterial cell wall

•GlycocalyxGlycocalyx

•FlagellaFlagella

•Axial filamentsAxial filaments

•Fimbriae and piliFimbriae and pili

GlycocalyxGlycocalyx

•Capsule (firm) or slime layer Capsule (firm) or slime layer (loose)(loose)–polysaccharide and/or polysaccharide and/or polypeptidepolypeptide

–Inhibits phagocytosisInhibits phagocytosis–Attaches to host surfacesAttaches to host surfaces–Protects against desiccationProtects against desiccation

• Outside cell wallOutside cell wall

• Usually stickyUsually sticky

• A capsule is neatly A capsule is neatly organizedorganized

• A slime layer is A slime layer is unorganized & looseunorganized & loose

• Extracellular Extracellular polysaccharide allows cell polysaccharide allows cell to attachto attach

• Capsules prevent Capsules prevent phagocytosisphagocytosis

GlycocalyxGlycocalyx

Figure 4.6a, b

Bacterialglycocalyx

Streptococcus pneumoniaecapsule

• Outside cell Outside cell wallwall

• Made of chains Made of chains of flagellinof flagellin

• Attached to a Attached to a protein hookprotein hook

• Anchored to Anchored to the wall and the wall and membrane by membrane by the basal bodythe basal body

• They propel They propel bacteria bacteria aroundaround

FlagellaFlagella

Flagella

•Rotate flagella to run or Rotate flagella to run or tumbletumble

•Move toward or away Move toward or away from stimuli (taxis)from stimuli (taxis)

•Flagella proteins are H Flagella proteins are H antigens antigens (e.g., (e.g., E. coliE. coli O157:H7) O157:H7)

Motile CellsMotile Cells

Peritrichous

Monotrichous

Lophotrichous

Types of Flagella

Types of Flagella

Main function: to propel bacteria to and from area’s of nutrients/toxic environments

Types of Flagella

Axial filamentsAxial filaments

•Present in spiral cellsPresent in spiral cells•Similar to flagella, but they wrap Similar to flagella, but they wrap

around the cellaround the cell•Corkscrew motion enables a Corkscrew motion enables a

bacterium such as bacterium such as T.pallidumT.pallidum (causative agent of Syphilis) to move (causative agent of Syphilis) to move effectively through body fluids effectively through body fluids (vaginal secretions)(vaginal secretions)

Fimbriae, pili and sex piliFimbriae, pili and sex pili

•Short thin appendagesShort thin appendages–Fimbriae and piliFimbriae and pili

•Help cells to adhere to Help cells to adhere to surfacessurfaces

–Sex piliSex pili

•Bridge between bacterial Bridge between bacterial cells for DNA transfercells for DNA transfer

DNA transfer through a sex pili

FimbriaeFimbriae

• Fimbriae allow Fimbriae allow attachment to attachment to teeth, stones teeth, stones in creeks, in creeks, plastic plastic catheter's in catheter's in hospitalshospitals

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

Fimbriae

E. coli

Intestinal mucosa

Cell wallCell wall

•Surrounds the plasma Surrounds the plasma membranemembrane–Protects the cell from Protects the cell from osmotic pressure changesosmotic pressure changes

–Lattice formed by Lattice formed by peptidoglycan (murein)peptidoglycan (murein)

• Prevents osmotic lysisPrevents osmotic lysis

• Made of peptidoglycan (in bacteria)Made of peptidoglycan (in bacteria)

Cell WallCell Wall

Figure 4.6a, b

Peptidoglycan Peptidoglycan (murein)(murein)

•N-acetylglucosamine N-acetylglucosamine (NAG)(NAG)

•N-acetylmuramic acid N-acetylmuramic acid (NAM)(NAM)–repeating disaccharides repeating disaccharides joined by polypeptidesjoined by polypeptides

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

• Linked by polypeptidesLinked by polypeptides

PeptidoglycanPeptidoglycan

Figure 4.13a

N-acetylglucosamine(NAG)

N-acetymuramic acid(NAM)

Peptide bridge

NAG

NAM

Peptide bridge

Gram-positive cellsGram-positive cells

•several well-organized several well-organized peptidoglycan layerspeptidoglycan layers

•teichoic acidsteichoic acids

Gram positive

Gram positiveS. aureus

• Teichoic acids:Teichoic acids:– Lipoteichoic acid links to plasma Lipoteichoic acid links to plasma

membranemembrane– Wall teichoic acid links to peptidoglycanWall teichoic acid links to peptidoglycan

• May regulate movement of cationsMay regulate movement of cations

• Polysaccharides provide antigenic Polysaccharides provide antigenic variationvariation

Gram-Positive cell wallsGram-Positive cell walls

Figure 4.13b

Gram Negative Cells

Gram-negative cellsGram-negative cells• a thin poorly-organized a thin poorly-organized

peptidoglycan layerpeptidoglycan layer

• outer membraneouter membrane– lipoprotein-lipopolysaccharide-lipoprotein-lipopolysaccharide-

phospholipid (LPS) phospholipid (LPS)

Gram-negative cells Gram-negative cells ((cont.cont.))

•outer membraneouter membrane–protects against protects against phagocytosis, penicillinphagocytosis, penicillinsugars in LPS act as sugars in LPS act as antigensantigens

lipid A acts as lipid A acts as endotoxinendotoxin

Outer membrane

peptidoglycan

Gram negative bacteria

Figure 4.13b, c

Gram negativeE. coli

Gram positiveNo outer membrane

Gram negativeWith an outer membrane

• Lipopolysaccharides, lipoproteins, Lipopolysaccharides, lipoproteins, phospholipids.phospholipids.

• Forms the periplasm between the outer Forms the periplasm between the outer membrane and the plasma membrane.membrane and the plasma membrane.

• Protection from phagocytes, complement, Protection from phagocytes, complement, antibiotics.antibiotics.

• O polysaccharide antigen, e.g., O polysaccharide antigen, e.g., E. coliE. coli O157:H7.O157:H7.

• Lipid A is an endotoxin.Lipid A is an endotoxin.

• Porins (proteins) form channels through Porins (proteins) form channels through membranemembrane

Gram-Negative Outer Gram-Negative Outer MembraneMembrane

•Thick Thick peptidoglycpeptidoglycanan

•Teichoic Teichoic acidsacids

•In acid-fast In acid-fast cells, cells, contains contains mycolic acidmycolic acid

•Thin Thin peptidoglycanpeptidoglycan

•No teichoic No teichoic acidsacids

•Outer Outer membranemembrane

Figure 4.13b, c

•MycoplasmasMycoplasmas–Lack cell wallsLack cell walls–Sterols in plasma Sterols in plasma membranemembrane

•ArchaeaArchaea–Wall-less, orWall-less, or–Walls of pseudomurein Walls of pseudomurein (lack NAM and D amino (lack NAM and D amino acids)acids)

Atypical Cell WallsAtypical Cell Walls

• Lysozyme digests disaccharide in Lysozyme digests disaccharide in peptidoglycanpeptidoglycan

• Penicillin inhibits peptide bridges in Penicillin inhibits peptide bridges in peptidoglycanpeptidoglycan

Damage to Cell WallsDamage to Cell Walls

Damage to cell wallsDamage to cell walls

•Lysozyme degrades Lysozyme degrades peptidoglycanspeptidoglycans

•Penicillin and other Penicillin and other antibiotics affect antibiotics affect synthesis of cell wallsynthesis of cell wall

PlasmaPlasma MembraneMembrane

Plasma MembranePlasma Membrane

Figure 4.14a

Plasma MembranePlasma Membrane• Phospholipid bilayerPhospholipid bilayer

• Peripheral proteinsPeripheral proteins

• Integral proteinsIntegral proteins

• Transmembrane Transmembrane proteinsproteins

Figure 4.14b

• Membrane is as Membrane is as viscous as olive oil.viscous as olive oil.

• Proteins move to Proteins move to functionfunction

• Phospholipids Phospholipids rotate and move rotate and move laterallylaterally

Fluid Mosaic ModelFluid Mosaic Model

Figure 4.14b

THE GRAM STAINTHE GRAM STAIN

• Crystal violet-iodine crystals form in Crystal violet-iodine crystals form in cellcell

• Gram-positiveGram-positive– Alcohol dehydrates peptidoglycanAlcohol dehydrates peptidoglycan– CV-I crystals do not leaveCV-I crystals do not leave

• Gram-negativeGram-negative– Alcohol dissolves outer membrane and Alcohol dissolves outer membrane and

leaves holes in peptidoglycanleaves holes in peptidoglycan– CV-I washes outCV-I washes out

Gram Stain MechanismGram Stain Mechanism

Gram positive

Gram negative

Gram stain technique

Know all four steps and why you are doing them!!!

REVIEWREVIEW

•We are conditioned to think of We are conditioned to think of bacteria as invisable, potentially bacteria as invisable, potentially harmful little creatures!!harmful little creatures!!

•Actually, relatively few species of Actually, relatively few species of bacteria cause disease in humans, bacteria cause disease in humans, animals and plants!!animals and plants!!

•After this course you will realize After this course you will realize that without bacteria, much of life that without bacteria, much of life as we know it would not be possible as we know it would not be possible !!!!

Bacteria and

Archaea Bacteria

Procaryotes

The Prokaryotes: The Prokaryotes: Domains Bacteria and ArchaeaDomains Bacteria and Archaea

•One circular chromosome, One circular chromosome, not in a membranenot in a membrane

•No histonesNo histones

•No organellesNo organelles

•Peptidoglycan cell wallsPeptidoglycan cell walls

•Binary fissionBinary fission

THE PROTEOBACTERIATHE PROTEOBACTERIA•Remember all organisms made Remember all organisms made

up of eukaryotic cells probably up of eukaryotic cells probably evolved from bacterialike evolved from bacterialike organism, which were the organism, which were the earliest forms of life!!!earliest forms of life!!!

•Include most of the G-, Include most of the G-, chemoheterotrophic bacteriachemoheterotrophic bacteria

•Have arisen from a common Have arisen from a common photosynthetic ancestorphotosynthetic ancestor

•ProteoProteobacteribacteriaa– Mythical Mythical

Greek god, Greek god, ProteusProteus, , who could who could assume assume many many shapesshapes

– Gram-Gram-negativenegative

Domain BacteriaDomain Bacteria

Alpha (Alpha ()--Proteobacteria)--Proteobacteria•Are capable of growth at Are capable of growth at

very low levels of nutrientsvery low levels of nutrients•Have unusual morphology, Have unusual morphology,

including protrusions such as including protrusions such as stalks or buds known as stalks or buds known as prosthecaeprosthecae

•They include agriculturally They include agriculturally important bacteria capable of important bacteria capable of inducing nitrogen fixationinducing nitrogen fixation

•Human pathogens:Human pathogens:–BartonellaBartonella–B.hensela B.hensela Cat-scratch Cat-scratch diseasedisease

–BrucellaBrucella BrucellosisBrucellosis

The The (alpha) Proteobacteria (alpha) Proteobacteria

RickettsiasRickettsias

•Rickettsias, Coxiella Rickettsias, Coxiella and and ChlamydiaChlamydia are obligate are obligate intracellular parasitesintracellular parasites

•They only reproduce inside a They only reproduce inside a mammalian cellmammalian cell

•Obligate intracellular parasites:Obligate intracellular parasites:– EhrlichiaEhrlichia - - Tick-borne, Tick-borne,

ehrlichiosisehrlichiosis– RickettsiaRickettsia - - Arthropod-borne, Arthropod-borne,

spotted spotted feversfevers•R. prowazekii R. prowazekii Epidemic Epidemic typhus typhus (lice)(lice)

•R. typhiR. typhi Endemic murine Endemic murine typhus typhus (rat fleas)(rat fleas)

•R. rickettsii R. rickettsii Rocky Mountain Rocky Mountain Spotted Spotted

Fever(ticks)Fever(ticks)


The The (alpha) Proteobacteria (alpha) Proteobacteria (Rickettsias)(Rickettsias)

Figure 11.1

• WolbachiaWolbachia. Live in . Live in insects and other insects and other animals animals

• Belongs to the Belongs to the Rickettsia generaRickettsia genera


• Have prosthecae:Have prosthecae:– CaulobacterCaulobacter. Stalked . Stalked

bacteria found in low bacteria found in low nutrient lakes as well as nutrient lakes as well as in laboratory in laboratory waterbaths—stalk helps waterbaths—stalk helps in the absorption of in the absorption of nutrientsnutrients

– HyphomicrobiumHyphomicrobium. . Budding bacteria found Budding bacteria found in lakes—when in lakes—when nutrients are low, stalk nutrients are low, stalk size increases to size increases to provide greater area for provide greater area for nutrient absorptionnutrient absorption


• Plant pathogen:Plant pathogen:– AgrobacteriumAgrobacterium

(invades plants & (invades plants & causes crown causes crown gall) gall)

– It inserts a It inserts a plasmid into plasmid into plant cells, plant cells, inducing the inducing the tumortumor

– Researchers are Researchers are very interested very interested in this organism in this organism b/c plant cells b/c plant cells are very difficult are very difficult to penetrateto penetrate


•Chemoautotrophic:Chemoautotrophic:–Oxidize nitrogen for energyOxidize nitrogen for energy

–Fix COFix CO22

•NitrobacterNitrobacter. NH. NH33++ NO NO22

––

•NitrosomonasNitrosomonas. NO. NO22–– NO NO33

––


•Nitrogen-fixing Nitrogen-fixing bacteria:bacteria:–AzospirillumAzospirillum

•Grow in soil, using Grow in soil, using nutrients excreted nutrients excreted by plantsby plants

•Fix nitrogenFix nitrogen–RhizobiumRhizobium

•Fix nitrogen in the Fix nitrogen in the roots of plantsroots of plants


Figure 27.5

•Are industrially importantAre industrially important

•They produce acetic acid They produce acetic acid (vinegar) from ethyl alcohol:(vinegar) from ethyl alcohol:–AcetobacterAcetobacter–GluconobacterGluconobacter


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BACTERIAL MORPHOLOGY: PROCARYOTIC AND EUCARYOTIC CELLS Chapter 4