chapter 3

• Diplococci


  Pairs of cocci
• Streptococci

  Chains of cocci
• Staphylococci

  Grape-like clusters of cocci
• Tetrads

  4 cocci in a square
• Sarcinae

  Cubic configuration of 8 cocci
• Coccobacilli

  Very short rods
• Vibrios

  Comma-shaped rods
• Spirilla

  Rigid helices
• Spirochetes

  Flexible helices
• Mycelium

  Network of long, multinucleate filaments
• Pleomorphic

  Organisms that are variable in shape
• Smallest bacteria

  Mycoplasma (0.3 μm)
• Average rod


  E. coli (1.1 to 1.5 by 2 to 6 μm)
• Very large bacteria

  Epulopiscium fishelsoni (600 by 80 μm)

  
• Common bacterial cell structures

  • Plasma membrane
  • Gas vacuole
  • Ribosomes
  • Inclusions
  • Nucleoid
  • Periplasmic space
  • Cell wall
  • Capsules and slime layers
  • Fimbriae and pili
  • Flagella
  • Endospore

  
• Plasma membrane

  Selectively permeable barrier, mechanical boundary of cell, nutrient and waste transport, location of many metabolic processes (respiration, photosynthesis), detection of environmental cues for chemotaxis

  
• Gas vacuole


  Provides buoyancy for floating in aquatic environments
• Ribosomes

  Site of protein synthesis
• Inclusions

  Storage of carbon, phosphate, and other substances; site of chemical reactions (microcompartments); movement
• Nucleoid

  Localization of genetic material (DNA)
• Periplasmic space

  In Gram-negative bacteria, contains hydrolytic enzymes and binding proteins for nutrient processing and uptake; in Gram-positive bacteria, may be smaller or absent
• Cell wall


  Protection from osmotic stress, helps maintain cell shape
• Capsules and slime layers

  Resistance to phagocytosis, adherence to surfaces
• Fimbriae and pili

  Attachment to surfaces, bacterial conjugation and transformation, twitching
• Flagella


  Swimming and swarming motility
• Endospore


  Survival under harsh environmental conditions
• Plasma membrane


  Encompasses the cytoplasm; absolute requirement for all living organisms
• Plasma membrane


  Selectively permeable barrier, interacts with external environment (receptors, transport systems, metabolic processes)
• Amphipathic lipids

  Polar ends (hydrophilic—interact with water), Non-polar tails (hydrophobic—insoluble in water)
• Peripheral membrane proteins

  Loosely connected to membrane; easily removed
• Integral membrane proteins

  Amphipathic (embedded within membrane); carry out important functions
• Bacterial membranes lack sterols but do contain sterol-like molecules, hopanoids

  
• Hopanoids stabilize membrane and mark microdomain boundaries
• Macronutrients

  • C, O, H, N, S, P
  • K, Ca, Mg, Fe
• Micronutrients (trace elements)

  • Mn, Zn, Co, Mo, Ni, Cu
• Growth factors

  Organic compounds essential for cell components or their precursors that the cell cannot synthesize
• Classes of growth factors

  • Amino acids
  • Purines and pyrimidines
  • Vitamins
• Passive diffusion

  Molecules move from region of higher concentration to one of lower concentration between the cell's interior and the exterior
• Facilitated diffusion


  Uses membrane bound carrier molecules (permeases) to transport molecules down concentration gradient

  
• Active transport


  Energy-dependent process that moves molecules against the concentration gradient