Orbita exam

Cards (142)

  • Binary fission
    The process by which prokaryotic organisms divide and reproduce (asexual reproduction)
  • Binary fission is not the same as mitosis or meiosis (will only happen in eukaryotic cells)
  • How Binary Fission Works
    1. Grow and elongate
    2. Replicate genetic material (DNA replication)
  • Generation time/Doubling time
    (in prokaryotes) The time it takes for a bacterial population to double in size
  • Some bacteria can divide into 2 cells once every 20 minutes under optimum conditions
  • The Bacterial Growth Cycle Under Laboratory Condition
    1. Lag Phase
    2. Log Phase
    3. Stationary Phase
    4. Death or Decline Phase
  • Lag Phase
    • No cell division
    • Cell synthesizes metabolites, enzymes, coenzymes, ribosomes and transport proteins needed for growth under prevailing conditions
  • Log Phase
    • Bacteria grow exponentially
    • Different species vary in terms of generation time or doubling time
    • Environmental conditions like temperature, pH and oxygen (for aerobes) have major influence for bacterial growth
  • As temperature increases
    Growth rate increases
  • Stationary Phase
    • No growth
    • Nutrient is exhausted; toxic by-products accumulate
    • Cells entering stationary phase undergo changes like synthesis of new starvation-specific proteins for survival
  • Death or Decline Phase

    • Cells die in greater number than the dividing cells as the culture medium accumulates toxic waste and nutrients are exhausted
  • Viable but not culturable (VBNC)
    Bacterial cells that are alive but cannot be detected by standard culturing techniques
  • VBNC state of marine bacteria are very much affected by the amount of nutrients in the environment, temperature, pH, salinity and pressure
  • Macronutrients needed for bacterial growth
    • Carbon
    • Oxygen
    • Nitrogen
    • Sulfur
    • Phosphorus
  • Micronutrients and trace elements needed for bacterial growth
    • Potassium
    • Calcium
    • Magnesium
    • Iron
    • Manganese
    • Cobalt
    • Zinc
    • Molybdenum
    • Copper
    • Nickel
  • Most marine bacteria also require small amounts of preformed amino acids, pyrimidines, purines and vitamins because they lack the biochemical pathways to synthesize these micronutrients
  • Sodium requirement of marine bacteria and archaea
    Most marine prokaryotes optimally grow at a concentration of NaCl similar to seawater (about 3.0 – 3.5% NaCl)
  • Psychrophilic (cold-loving) prokaryotes
    • Optimum growth temperature less than 15°C, max of 20°C and min of 0°C or less
  • Psychrotolerant bacteria

    • Can grow as low as 0°C but have an optimum of 20-35°C
  • Thermophilic prokaryotes
    • Can grow at 60°C
  • Hyperthermophiles
    • Can grow above 80°C, majority belong to Archaea domain
  • Barotolerant organisms
    • Can grow from 1-400 atm but have low metabolic and growth rate
  • Obligate or extreme barophiles
    • Can grow above 400 atm
  • Types of organisms based on oxygen requirement
    • Obligate aerobes
    • Obligate anaerobes
    • Facultative anaerobes
    • Facultative aerobes
  • UV-screening products in bacteria
    • Mycosporine-like amino acids
    • Scytonemin (a complex aromatic compound in cyanobacterial sheaths)
  • Mechanisms of UV resistance in some coral-associated bacteria
    • Enhanced activity of NAD(P)H quinone oxidoreductase, a powerful antioxidative enzyme
  • Extreme halophiles
    • Several genera of Archaea that can grow at very high NaCl concentrations (15–35%)
  • Extreme halophilicity
    Rare in Bacteria, but Salinibacter rubrum is an exception
  • Major divisions of the ocean
    • Pelagic (water column)
    • Benthic (bottom)
  • Pelagic provinces
    • Neritic (low tide line to shelf break)
    • Oceanic (open ocean)
  • Ocean zones
    • Epipelagic (0-200 m)
    • Mesopelagic (200-1000 m)
    • Bathypelagic (1000-4000 m)
    • Abyssopelagic (4000-6000 m)
    • Hadopelagic (6000 m and below)
  • Marine snow
    A continuous shower of organic material falling from upper waters to the deep ocean, composed of a variety of organic matter, protists, fecal matter, sand and other inorganic dust
  • Levels of marine microbes in marine snow are typically 100-10000 fold higher than in the bulk water column
  • Deep-sea organisms rely heavily on marine snow as an energy source
  • Biofilms
    A collection of microbes bound to a surface
  • Matter, sand and other inorganic dust
    • Can form through abiotic processes (i.e. extrapolymeric substances made by phytoplankton and bacteria)
  • Aggregates
    • Contain active complex assemblages of bacteria and bacterivorous protists
    • Levels of marine microbes in marine snow are typically 100-10000 fold higher than in the bulk water column
    • Grow over time and may reach several centimeters in diameter, traveling for weeks before reaching the ocean floor
  • Marine sediments
    • Derived from continental transport and sedimentation of biological products
    • Provide important habitats for microorganisms
  • Other types of sediment that provide special habitats for microbes include those in salt marshes, mangroves and coral reefs
  • Biofilms
    • Consist of a collection of microbes bound to a solid surface by their extracellular polymeric substances (EPS) which trap organic and inorganic components
    • Often called as "cities of microbes"
    • Found in both living or non-living surfaces