Functional Anatomy of Prokaryotic Cells

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Functional Anatomy of Prokaryotic Cells
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All living cells can be classified into two
groups based on certain structural functional
characteristics

• Prokaryotes
• Eukaryotes

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They are chemically similar in the sense that
they both contain nucleic acidsproteinslipid
scarbohydrates
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The distinguishing characteristic of prokaryotes
eukaryotes

• Proka. 0.2-2.0 microm
• DNA is not enclosed within a membrane
  (singularly arranged chromosome)
• DNA is not associated with histonesspecial
  chromosomal proteins found in euk

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• no membrane-enclosed organelles
• cell wall almost always contain
  the complex polysaccharide peptidoglycan
• divided by binary fission(DNA is
  copied the cell splits into two cells

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The distinguishing characteristic of prokaryotes
eukaryotes

• Euka. 10-100microm.
• DNA is found in cells nucleus
  which is separated from the cytoplasm by nuclear
  membrane (DNA is found in multiple chromosomes)
• DNA is associated with histones

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• the have a number of membrane-enclosed
  organelles(mitochondria , endoplasmic reticulum
  Golgi complex lysosomes)
• cell wall is chemically simple
• cell division usually involves
  mitosis

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PROKARYOTES
EUKARYOTES
BACTERIA
ARCHAEA
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BACTERIA
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Naming and Classifying Microorganisms

• The system for nomenclature for microorganisms
• The scientific name is binomial
• The First is the genus name
• The Second is the species name
• The first letter of the genus name is always
  capitilized
• Staphylococcus (genus) aureus (species)
• Both are underlined or italicized
• Staphylococcus aureus
• Staphylococcus aureus

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Identification of bacteria

• Thousands of bacteria species are differentiated
  by many factors including
• morphology (shape , size arrangement)Chemi
  cal composition (staining)Nutritional
  requirementsBiochemical activitiesSource
  of energy

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MorphologySize -- Shape -- ArrangementSize
0.2 2.0 micrometer in
diameter 2.0 -- 8.0 micrometer in
length Bacterial shapes are
determined by heredity
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Shapes Arrangements of Bacteria
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cocci

• Coccusspherical round or oval
• Diploccocipairs
• Streptococcichainlike
• Staphylococcigroups (grapelike)

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Bacilli

• Bacilli rode shape
• mostly Single
• Diplobacillipairs
• Streptobacollichais
• Coccobacillioval

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spiral

• Have one or more twists----never straight
• Vibrioscurved rods
• Spirillahelical
• Spirocheteshelical flexible

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Structure of Bacteria
Essential structures cell wall cell membrane
Cytoplasm nuclear material

• Particular structures
• capsule
• flagella
• pili
• spore

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Structure of Bacterial cell
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Structures
structures external to the cell wall
cell wall itself
structures internal to the cell wall
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glycocalyx (capsule)flagellaaxial
filamentsfimbriaepili
structures external to the cell wall
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Glycocalyx

• Glycocalyxsugar coatsub.that surround
  cellsstickyexternal to cell wall
• Polysaccharide , polypeptide or both
• If attached to cell wall capsule (well defined)
  or slim layer(not defined)

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Glycocalyx

• Capsule or slime layer
• Functions
• Help adherence attachment
• of bacterial cells to surfaces.
• Provide nutrients
• Protect bacterial cells against dehydration
• Increase virulence of bacteria
• Protect the pathogenic bacteria.
• From phagocytosis by host
• WBC
• .

The degree of which bac. Cause disease
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Streptococcus pneumoniaepneumoniarespiratory
tract
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FLAGELLA

• Some bacteria are motile
• Locomotory organelles- flagellalong filamentous
• appendages
• External to cell wall

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Flagellar arrangements outside bacterial cell
Atrichous lack flagella
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Monotrichous single flagellum at one end
Amphitrichous- flagella at both end of bacterial

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Lophotrichous-2 or more arising from one end of
bacterial cell
Peritrichous Flagella distributed over the
entire surface, low motility

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Motilityis the ability of bac. to move
itselfone directiondifferent directionswaves
toward a favorable environmentoraway from an
adverse conditions chemotaxisaway from
chemicalslightphototaxis
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Advantages of flagella

• Identification of Bacteria
• H-antigen flagellar protein is useful for
  distinguish variations within speciesMotility
  of bacteria

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Axial filaments

• similar to flagellum
• bundles of fibrils that arise at the end of
  bacterial cell
• Spiral motion
• Snake-like movement
• spirochetes have unique structure motility

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Pili (fimbriae)

• hair-like projections of the cell
• (shorter and thinner than flagella)
• Occur at the poles or can evenly distributed on
  bacterial cell
• Fibriae are involve in bacterial attachment to
  surfaces and resistance to phagocytosis cause
  disease
• Neisseria gonorrhoeaegonorrhea

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Pili

• Chemical nature is pilin
• bacterial conjugation
• Sex pili effect the transfer of conjugative
  plasmids

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Extracellular Appendages

• FIMBRIE FLAGELLA

• SEX PILI

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Structure of Bacterial cell
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Composition structure of cell wall
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Bacterial cell wall

• All prokaryotes have cell wall
• The cell wall of bacterial cell is
• Complex
• Surround the fragile plasma membrane
  (cytoplasmic)
• Protect the interior of cell

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The major functions of cell wall

• Prevent bacterial cells from rupturing, when
  water pressure inside the cell is greater than
  that outside the cell , so it is essential for
  bacterial viability
• Countering the effects of osmotic pressure
• Providing a rigid platform for surface
  appendages- flagella, fimbriae, and pili all
  originate from the wall and extend beyond it

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Cell wall major functions

• Site of action of antibiotics, the most important
  one
• Resistance of Antibiotics
• Shape of bacteria

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Functions of cell wall

• The chemical composition of cell wall is used to
  differentiate major types of bacteria.
• Be the sites of major antigenic determinants of
  the cell surface
• Provide the immunological distinction among
  bacteria

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• Bacterial cell wall is composed of macromolecular
  net work peptidoglycan
• Peptidoglycan peptide glycan
• Peptidoglycan consists of repeating disaccharide
  attached by polypeptides , that surrounds
  protects bacterial cell

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Cell Wall

• Disaccharide portion is mad up of
• Monosaccharides
• N-acetylglucosamine
• (NAG)
• N-acetylmuramic acid
• (NAM)

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Cell Wall

• Alternating (NAG) ( NAM) molecules are linked
  in rows to from a carbohydrate backbone (glycan
  portion )
• Adjacent rows are linked by polypeptides
• (peptide portion)

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Cell Wall
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• Penicillin interferes with final linking of the
  peptidoglycan rows by peptide
• bac.cell wall is weakened the cell undergoes
  lysis
• this destruction caused by rupture of the
  plasma membrane the loss of cytoplasm

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Gram positive bacteriacell wall consists of many
layers of peptidiglycan forming a thick , rigid
structure

• Cell wall of Gram positive bac. Contain
• Teichoic acids consist primarily of
• an alcohol (glycerol or ribitol)
• phosphate

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Teichoic acid classes
Lipoteichoic acid spans the peptidoglycan layer
is linked to the plasma membrane
Wall teichoic acid linked to the peptidoglycan
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Special components of Gram positive cell wall

• Teichoic acid

SPA / M POTEIN
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• Teichoic acid
• Regulate the movement of cations (ve ions) into
  out of the cell
• Assume in cell growth
• Provide wall s antigenic specificity diagnosis

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Gram negative bacteria cell wall

• Consist of one layer of peptidoglycan
• an outer membrane
• Do not contain teichoic acid
• the peptidoglycan is bonded to lipoproteins
• (lipids linked to proteins) in the outer
  membrane

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The outer membrane of Gm.-ve bac, consists of

• Lipopolysaccharides
• lipoproteins
• phospholipids

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Lipopolysaccharides
O polysaccharides antigen
Lipid portion Lipid A endotoxin
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Porin is a proteins in the outer membrane which
is important in the permeability of outer membrane
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Cell wall structure and Gram stain

• GRAM STAIN TECHNIQUE

• CELL WALL OF GVE AND G-VE BACT.

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Atypical cell walls

• 1- No or very little cell wall material
  Mycoplasma are the smallest bacteria that can
  reproduce outside living cell (sterols in the
  plasma membranes for protection)
• 2- Archaea unusual wall-- No peptidoglycan, ,
  proteins and polysaccharides.
• 3- Acid-fast cell walls contain high constration
  (60) of Waxy material outside the
  peptidoglycan. Mycolic acids prevent uptake of
  stains.

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Damage to the cell wall

• Chemicals that damage bact. Cell wall often do
  not harm the cells of an animal host .Why??
• When bacteria are treated with
• 1) enzymes that are lytic for the cell wall
  e.g. lysozyme (tears,mucus, saliva)
• Active on major cell wall components of most
  Gram ve bact.
• back bone disaccharide
  wall-less cell (protoplast)
• When Gram ve bact. Treated with lysozyme cell
  wall is not destroyed to the same extant as in
  Gram ve bact. Why ?? (outer membrane)
  (spheroplast)

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• Effect of "lysozyme", which is found naturally in
  tears, mucus, and saliva.-Gram positives are
  most susceptible and typically they burst (lyse)
  or, in favorable environments, they may form
  "protoplasts", which have no cell wall. -Gram
  negatives are less susceptible and some of the
  cell wall material remains (spheroplasts)--gt Can
  only survive in favorable conditions as they are
  weak.

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Damage to the cell wall

• 2) antibiotics that interfere with biosynthesis
  of peptidoglycan, wall-less bacteria are often
  produced.
• antibiotics that damage bact. Cell wall often
  do not harm the cells of an animal host .Why??

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Structure of Bacterial cell
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Structures internal to the cell wall
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Structures internal to the cell wall
Plasma or cytoplasmic membrane

• Is a thin structure lying inside the cell wall
  enclosing the cytoplasm
• consist primarily of phospholipids proteins

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Functions of Plasma membrane

• Selective permeability certain molecules
  ions pass through the membrane , but others
  prevented from passing through it
• Breakdown of nutrients and the production of
  energy ( contain enzymes catalyzing the chemical
  reaction)
• Some antibiotics and antibacterial agents kill
  bacteria by attacking the plasma membrane

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Damage of plasma membrane

• Many antibiotics have effect on plasma membrane
• Polymyxins disrupting phospholipids of the
  plasma membrane
• Alcohols ammonium compounds used as
  
  disinfectants

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Structures within the bacterial cell

• Cytoplasm thick aqueous (80 water)
  semitransparent.
• Contains organic molecules and inorganic ions.
  Proteins(enzymes) , carbohydrates , lipids
• The major structures in the cytoplasm are
• Nucleoid, ribosomes, inclusions

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The major structures in the cytoplasm are

• Nucleoid, nuclear area containing DNA
• Ribosomes
• Inclusions reserve deposits

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Nuclear material
Plasmids .
Single, long, double stranded circular
DNAbacterial chromosome. Carry all the genetic
information required for cell structure function
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plasmid

• extra-chromosomal DNA
• Small,circular,doubl-stranded DNA .not connected
  to bact. Chromosome, replicate independently
• May be gained or lost. Without harming bact.
• Can be transfer from one bact. To other
  (biotechnology)
• 5-100 genes))Cary genes for
• antibiotic resistance,
• tolerance to toxic metals,
• production of toxins and synthesis of enzymes

Plasmids .
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Nuclear material

• No nuclear membrane,
• absence of nucleoli, hence known as nucleic
  material or nucleoid,
• one to few per bacterium.

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Ribosomes

• Sites of protein synthesis
• Composed of two subunits made of protein and
  ribosomal RNA.
• Prokaryotic ribosomes are 70S while Eukaryotic
  ribosomes are 80S.

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• Erythromycin and chloramphenicol attach to 50 S
  subunit
• Streptomycin and gentamicin attach to 30 S
  subunit and inhibit protein synthesis.
• Bacterial cell can be killed by antibiotic while
  eukaryotic cell remains unaffected. Why???

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Inclusions

• Several kinds of reserve deposits within the
  cytoplasm
• Cells may accumulate certain nutrients when they
  are plentiful use them when the environment is
  deficient
• Their number depend on bact. Species
  identification

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Inclusions

• Reserve deposits
• Metachromatic granules.
• Polysaccharide granules carbohydrate
• Lipid inclusions lipid storage material
• Sulphur granules energy server
• Carboxyzomes enzymes photosynthesis
• Gas Vacuoles
• Magnetosomes

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Inclusions

• Metachromatic granules large inclusions
• some time stain red with blue dye
• have diagnostic significance
• stores inorganic phosphate
• Corynebacterium diphtheriae

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Endospores (spores)

• Resting structures
• Clostridium tetanus gas gangrene food
  poisoning
• Bacillus anthrax
• Highly durable dehydrated cells with thick walls
  additional layers which formed internal to the
  bact. cell membrane

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• Endospores when released into environment they
  survive
• -- extreme heat
• --lack of water
• --exposure to many toxic chemicals radiation

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• Sporulation sporogenesis
• formation of endospore
• (endospre forming bact.)
• This occur when nutrient (carbon , nitrogen
  source ) becomes unavailable or scarce
• Germination formation of vegetative form

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Endospores (spores)

• Identification of Bacteria
• Pathogenesis
• Resistance

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• One vegetative cell single
  endospore
• Single endospore one vegetative
  cell
• Not a means of reproduction
• protection

Sporulation
germination
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• Endospores are clinically important
• Food industry
• Resist heating
• Freezing
• Desiccation
• Use of chemicals radiation
• Some bact. Produce toxins

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Bacterial Spores

• BACILLUS ANTHRAX

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First Term Exam. Good Luck