bateria

• Prokaryote


  Comes from the Greek words for pre-nucleus
• Eukaryote


  Comes from the Greek words for true nucleus
• Prokaryotic cell


  • Glycocalyx (external to cell wall, viscous and gelatinous, made of polysaccharide and/or polypeptide)
  • Flagella (filamentous appendages external to cell, propel bacteria, made of protein flagellin, have filament, hook, and basal body)
  • Axial filaments (also called endo-flagella, found in spirochetes, anchored at one end, rotation causes corkscrew movement)
  • Fimbriae (hairlike appendages for attachment)
  • Pili (involved in motility like gliding and twitching, also involved in conjugation and DNA transfer)
• Cell wall


  • Prevents osmotic lysis and protects cell membrane, made of peptidoglycan (in bacteria), contributes to pathogenicity
• Protoplast


  Wall-less gram-positive cell
• Spheroplast


  Wall-less gram-negative cell
• L forms


  Wall-less cells that swell into irregular shapes
• Plasma (cytoplasmic) membrane


  • Phospholipid bilayer that encloses cytoplasm, has peripheral and integral/transmembrane proteins
• Nucleoid


  • Bacterial chromosome (circular thread of DNA with genetic information), plasmids (extrachromosomal genetic elements)
• Ribosomes


  Sites of protein synthesis, made of protein and ribosomal RNA, 70S (50S + 30S subunits)
• Inclusions


  • Metachromatic granules (phosphate reserves)
  • Polysaccharide granules (energy reserves)
  • Lipid inclusions (energy reserves)
  • Sulfur granules (energy reserves)
  • Carboxysomes (RuBisCO enzyme for CO2 fixation during photosynthesis)
  • Gas vacuoles (protein-covered cylinders that maintain buoyancy)
  • Magnetosomes (iron oxide inclusions that destroy H2O2)
• Endospores


  Resting cells produced when nutrients are depleted, resistant to desiccation, heat, chemicals, and radiation, produced by Bacillus and Clostridium
• Bacterial cell size and shape

  • Average size 0.2-2.0 μm diameter, 2-8 μm length, most are monomorphic (single shape), some are pleomorphic (many shapes), common shapes include bacillus (rod), coccus (spherical), spiral, vibrio, spirillum, spirochete, star-shaped, rectangular
• Bacterial cell arrangements


  • Pairs (diplococci, diplobacilli)
  • Clusters (staphylococci)
  • Chains (streptococci, streptobacilli)
  • Groups of four (tetrads)
  • Cubelike groups of eight (sarcinae)
• Bacillus


  Rod-shaped bacteria
• Gram-positive cell wall


  • Thick peptidoglycan, teichoic acids
• Gram-negative cell wall


  • Thin peptidoglycan, outer membrane
• Teichoic acids


  Lipo-teichoic acid links cell wall to plasma membrane, wall teichoic acid links peptidoglycan, carry negative charge, regulate cation movement, provide antigenic specificity
• Gram-negative cell wall


  • Periplasm between outer membrane and plasma membrane contains peptidoglycan, outer membrane made of polysaccharides, lipoproteins, and phospholipids, protects from phagocytes, complement, and antibiotics, made of lipopolysaccharide (LPS) with O polysaccharide antigen and lipid A endotoxin, has porins (protein channels)
• Differences between gram-positive and gram-negative cell walls

  • Gram-positive: 2 rings in basal body of flagella, produce exotoxins, high susceptibility to penicillin, disrupted by lysozyme
  • Gram-negative: 4 rings in basal body of flagella, produce endotoxins and exotoxins, low susceptibility to penicillin
• Acid-fast cell walls


  • Like gram-positive, waxy lipid (mycolic acid) bound to peptidoglycan, found in Mycobacterium and Nocardia, stain with carbolfuchsin
• Mycoplasma cell walls


  • Lack cell walls, have sterols in plasma membrane
• Archaea cell walls


  • Wall-less, or walls of pseudomurein (lack NAM and D-amino acids)
• Taxonomy


  The science of classifying organisms
• Taxon


  A group of organisms
• Phylogeny


  The study of the evolutionary history of organisms
• Limitations of a two-kingdom classification system
• Scientific names are used to provide a consistent way to identify organisms
• The Study of Phylogenetic Relationships

  1. Taxonomy shows degree of similarity among organisms

  2. Systematics, or phylogeny, is the study of the evolutionary history of organisms

  
• Linnaeus proposed kingdoms Plantae and Animalia


  1735
• Bacteria and fungi put in kingdom Plantae (Nägeli); Kingdom Protista proposed for bacteria, protozoa, algae, and fungi (Haeckel)


  1800s
• Prokaryote introduced to distinguish cells without a nucleus


  1937
• Murray proposed Kingdom Prokaryotae


  1968
• Whittaker proposed five-kingdom system

  1969
• Eukarya


  Domain containing animals, plants, and fungi
• Bacteria


  Domain containing prokaryotic cells
• Archaea


  Domain containing methanogens, extreme halophiles, and hyperthermophiles
• Eukaryotes originated from infoldings of prokaryotic plasma membranes
• Endosymbiotic bacteria developed into organelles
• Micron (μ)


  Unit of length equal to 10^-6 meter