Bacterial cell.ppt

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Bacterial cell.ppt Powered By Docstoc
					Dr. Alvin Fox



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                 Key Words
Prokaryotic                           Outer membrane
Eubacteria (Bacteria)                 Periplasmic space
Archaebacteria (Archaea)              Oxidative phosphorylation
Eukaryotic                            Spheroplast/protoplast
Plasmid                               Flagella
Chromosome                            Chemotaxis
Ribosome                              Axial filament
Peptidoglycan (murein, mucopeptide)   Periplasmic binding protein
Gram stain                            Permeases
Gram negative                         Storage Granules
Gram positive                         Pili (fimbriae)
Cell envelope                         Capsule (slime layer, glycocalyx)
Cell membrane                         Endospore (spore)
Cell wall
                                                                2
         EUKARYOTES

 PROKARYOTES



BACTERIA ARCHAEA

                   3
Prokaryotes (Bacteria)
• Eubacter "True" bacteria
  –   human pathogens
  –   clinical or environmental
  –   one kingdom
• Archaea
  – Environmental organisms
  – second kingdom
                                  4
            Eukaryotes
• Other cell-based life e.g.
– plants
– animals
– fungi



                               5
Prokaryotic Cell (versus Eukaryotic
               Cell)

  •   Not compartmentalized
  •   Cell membranes lack sterols (e.g. cholesterol)
  •   Single circular chromosome
  •   Ribosomes
            - 70S
            - subunits
        •       30S (16S rRNA)
        •       50S (5S & 23S rRNA)




                                                       6
             Bacteria versus
             Archaebacteria
• Eubacteria
  – peptidoglycan (murein)
  – muramic acid

• Archaebacteria
  – pseudomurein
  – no muramic acid



                               7
       Bacteria versus
       Archaebacteria

• 16S rRNA
  – sequence different




                         8
    Eukaryotic cell                      Prokaryotic cell
         (e.g. animal)             Gram +     Flagellum
Rough endoplasmic        Cell membrane     Nucleoid          Cell wall
reticulum
             Nucleus




                                   Gram -
                            Pili


                                                              Granule
                         Capsule
           Cytoplasm
                          Cell (inner) membrane       Outer membrane
Mitochondria                                                     9
                               Ribosomes        Cell wall
            Bacteria
• Plasmids
 • Extra-chromosomal DNA

 • multiple copy number

 • coding
    - pathogenesis factors
    - antibiotic resistance factors


 • bacterial replication              10
The Cell Envelope




Gram Positive   Gram Negative



                                11
 Oxidative phosphorylation occurs at cell membrane
 (since there are no mitochondria).


Cell Wall

                 Cytoplasm                 Cell membrane




The cell wall is outside of cell membrane
  – rigid, protecting cell from osmotic lysis.    12
                                       GRAM POSITIVE
                            Lipoteichoic acid      Peptidoglycan-teichoic acid




                    Cytoplasmic membrane

                                                   Cytoplasm

                                         GRAM NEGATIVE             Porin
                                                                                 Lipopolysaccharide
Periplasmic space




                    Outer Membrane                      Braun lipoprotein



                    Inner (cytoplasmic) membrane
                                                   Cytoplasm                                    13
            Outer Membrane
    Gram negative bacteria
•   major permeability barrier
•   space between inner and outer membrane
     – periplasmic space
        vstore degradative enzymes
•   Gram positive bacteria
•   no periplasmic space

                                             14
               GRAM NEGATIVE
               CELL ENVELOPE
Outer Membrane
(Major permeability barrier)                                   Lipopolysaccharide
                                                  Porin




                          Braun lipoprotein




Periplasmic space                                     Degradative enzyme

                               Periplasmic binding protein
Inner (cytoplasmic) membrane                                      Permease




                               Cytoplasm                                     15
              GRAM POSITIVE
              CELL ENVELOPE
      Degradative enzyme




     Lipoteichoic acid      Peptidoglycan-teichoic acid




Cytoplasmic membrane

                           Cytoplasm
                                                          16
           FLAGELLA
•   Some bacteria are motile
•   Locomotory organelles- flagella
•   Taste environment
•   Respond to food/poison
    – chemotaxis

                                      17
• Flagella
  – embedded in cell membrane
  – project as strand
  – Flagellin (protein) subunits
  – move cell by propeller like action




                                         18
        Axial filaments

– spirochetes
– similar function to flagella
– run lengthwise along cell
– snake-like movement



                                 19
     Making Wall-less Forms
•   Result from action of:
    – enzymes lytic for cell wall
    – antibiotics inhibiting peptidoglycan biosynthesis

•   Usually non-viable

•   Wall-less bacteria that don’t replicate:
    – spheroplasts (with outer membrane)
    – protoplasts (no outer membrane).

•   Wall-less bacteria that replicate
    – L forms
                                                          20
Naturally Wall-less Genus
    • Mycoplasma




                            21
     Pili (fimbriae)
• hair-like projections of the cell
• sexual conjugation
• adhesion to host epithelium




                                      22
Capsules and slime layers
•   outside cell envelope
•   well defined: capsule
•   not defined: slime layer or glycocalyx
•   usually polysaccharide
•   often lost during in vitro culture
•   protective in vivo




                                             23
    Endospores (spores)
• Dormant cell
• Produced when starved
• Resistant to adverse conditions
  - high temperatures
  - organic solvents
• contain calcium dipicolinate
• Bacillus and Clostridium

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posted:7/5/2014
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