Introduction To Prokaryotes(external)

Introduction To Prokaryotes(external)

1. domain

   • bacteria
   • archaea

2. definition

   • a group of organisms that lack of nucleus
   • most are unicellular but a few prokaryotes have multicellular life cycles

3. shape

   • coccus
     • diplococci
     • staphylococci
     • streptoccoci
   • bacillus
     • diplobacilli
     • streptobacilli
   • Spiral
     • vibrio
     • spirochetes
     • spirillum
   • additional shape
     • unusual
       • star-shaped
       • square
       • triangular
     • pleomorphic
       • within a population various shapes
     • no fixed shape
       • cellwall-less

4. size

   • 0.2 to 2.0 mikrometer in diameter
   • 2 to 8 mikrometer in length

5. External to cell wall

   • Glycocalyx
     • Definition
       • substances that surround the cell
     • Type of glycocalyx
       • Capsule
         • substances that is organized and firmly attached to the cell wall
       • Slime layer
         • substances that unorganized and loosely attached to cell wall
     • Functions
       • protection from phygocytosis
       • sources of nutrients
       • attachment to various surface
       • protect a cell from dehydration
   • Flagella
     • Definition
       • thread-like,locomotor appendages extending outward from plasma menbrane and cell wall
     • Types
       • monotrichous
       • Amphitrichous
       • Peritrichous
       • Lophotrichous
     • Functions
   • Axial filaments
     • spiral around cell
     • bundles of fibrils arise at the ends of the cell beneath outer sheath
   • Fimbriae and Pili
     • Fimbriae
       • occur at poles of bacterial cells
     • Pili
       • longer than fimbriae
       • only one or two per cell
       • joint bacterial cell for transfer of DNA from one to another
     • definition
       • hairlike appendages that shorter,straighter and thinner than flagella

6. Cell wall

   • composition and characteristics
     • composed of peptidoglycan that consist of repeating disaccharide
     • the disaccharide is made up of N-acetylglucosamine and N-acetylmuramic acid that are linked by glycosidic acid and peptide bond
   • Functions
     • prevent bacterial cell from rupturing when water pressure inside cell is greater than water pressure outside cell
     • contributes to pathogenicity
     • classification
     • maintain characteristics shape
     • provides a rigid platform
     • the cell wall of a bacteria is different
   • Types
     • Bacteria's cell wall
       • Gram-positive bacteria
         • consists of many layer of peptidoglycan
         • Thick peptidoglycan layer
           • 90% of cell wall is peptidoglycan
         • periplasmic space lies between plasma membrane and cell wall and smaller than Gram-Negative bacteria
         • enzymes secreted is exoenzymes aid in degradation of nutrients
         • contain teichoic acid
           • make Gram-positive cell wall become acidic
           • classifying species of Gram-positive bacteria
           • negatively charged
           • cell wall do not degrade easily
       • Gram-negative bacteria
         • consists of one or a few of pepetidoglycan
         • consists of outer membrane that provide a barrier to certain antibiotics,lysozyme, detergent, heavy metal, bile salt and certain dyes
         • peptidoglycan is bonded to lipoprotein
         • do not contain teichoic acid
         • Gram-negative cells are more vulnerable to mechanical breakage because minimal amount of peptidoglycan
         • contain lypopolysaccharide that function as antigens
         • periplasmic space contain high concentration of degrading enzymes
     • Archaea's cell wall
       • Gram-positive Archaea
         • Pseudomurein that consists of L-amini acid, N-acetyltalosaminuronic acid
         • contain single thick hmogenous layer
       • Gram-negative archaea
         • have surface with protein or glycoprotein subunits
         • resistant to lysozyme, and beta-lactam antibiotics