microbial structures

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alishahodge
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170820
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microbial structures
Updated:
2012-09-14 06:29:49
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microbial structures
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chapter 4 intro micro
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  1. prokaryotes 2 domains
    • 1 archaea (ancient, unusual bacteria)
    • 2 Bacteria
  2. eukaryotes:include all other organisms into a single domain
    plants, animals, fungi, protozoa, algae
  3. DNA not found within nucleus
    DNA single, circularly arranged chromosome
    no membrane bound organelles
    cell walls contain peptidoglycan
    replicate/divide by binary fission
    prokaryotes
  4. DNA found within a nucleus
    DNA is found in multiple chromosomes
    cells contain membrane bound organelles-mitochondria nuclei,chloroplasts, etc.
    cell walls simple in structure
    cells divide by mitosis
    Eukaryotes
  5. Prokaryotes
    • bacterial species are differentiated by many factors including:morphology (shape and other structures
    • chemical composistion(satining characteristics)
    • nutritional requirements
    • biochemical activities
    • sources of energy
  6. size,shape and arrangement of bacterial cells
    • size- 0.2-2.0 um indiameter and 2-8um in length; comparative examples tiny,small,large
    • shape - coccus,bacillus,spiral
    • arrangements - single, pair, chains, clusters
  7. cocci
    • spheres
    • pair=diplococci
    • chains=streptococci
    • clusters=staphylococci
  8. variation of diplocicci shapes
    coffee bean and lancet shaped
  9. bacilli
    • rods
    • gram negatives are typically found singly but others can be described by following
    • pair=diplobacilli
    • chains=streptobacilli
    • Not found in clusters
    • tiny rods often referred to as coccobacilli
  10. spiral-shaped bacteria
    • have one or more curves-they are never straight
    • single curve,comma shaped=vibrio
    • corkscrew and rigid=spirillum
    • corkscrew and flexible=spirochete
  11. glycocalyx (aka sugar coat)
    • external to cell wall
    • not all bacteria secrete these substances
    • composed of polysaccharides,polypeptides or a combination
    • when organized and firmly attached to the cell wall is called a capsule
    • when unorganized and loosely attached is called a slime layer
  12. glycocalyx purpose
    • to protect the organism from dehydration
    • from phagocytosis(increases its virulence)
    • also helps organisms attach to various surfaces
  13. flagella
    • these are long filamentous appendages that enable bacteria to move-which can be advantageous to the bacteria have
    • not all bacteria have these.
    • composed of 3 parts
    • filament,hook,basal body
  14. fimbriae
    enable a cell to adhere to surfaces or to other cells (not used for mobility)
  15. pili
    join bacterial cells in preperation for the transfer of DNA from one cell to another (a process called conjugation) (not used for mobility)
  16. cell wall
    • complex semi rigid structure responsible for the shape of the cell
    • major functions:
    • prevent bacterial cells from rupturing
    • maintains the shape of the bacterium
    • serves as an anchor for flagella
  17. gram positive cell walls
    • consists of many layers of peptidoglycan
    • also contains teichoic acid (consists primarily of an alcohol and phosphate)
    • 2 classes-lipoteichoic acid (linked to the plasma membrane) and wall teichoic acid (linked to the peptidoglycan layer
  18. gram negative cell walls
    • consists of only 1 or a very few layers of peptidoglycan and an outer membrane
    • the outer membrane consists of lipoproteins, lipopolysaccharides and/or phosopholipids which have several specialized functions
  19. nuclear area (nucleoid)
    • contains a single long, continuous and circularly arranged thread of double staranded DNA called the bacterial chromosomes -the cells genetic information
    • ¬†attached to the plasma membrane
  20. plasma membrane
    • functions as a selective barrier-certain molecules and ions pass thru and others dont
    • important to the breakdown of nutrients and production of energy
  21. ribosomes
    • site of protein synthesis
    • composed of 2 subunits each of which consists of proteins and ribosomal RNA (rRNA)
  22. endospores
    are highly durable dehydrated cells with thick walls and additional layers, highly resistant and can survive extreme heat,lack of water,exposure to many toxic chemicals and radiation ,true ones are found only in gram + bacteria,process of this formation is called sporulation or sporogenesis, opposite process is called germination

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