lec 4

• Binary fission


  1. Grow and elongate

  2. Replicate genetic material (DNA replication)

  
• Generation time


  How Quickly Bacterial Populations Can Grow?

  (in prokaryotes) Doubling time
• Some bacteria can divide into 2 cells once every 20 minutes under optimum condition
• 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
• Marine bacteria isolated from 10°C grow with generation times of about 7-9 hours while those at 25°C typically grows every 0.7 to 1.5 hours
• All organisms have minimum, optimum and maximum temperature for growth and this reflects their evolution
• Above the minimum, optimum and maximum temperature metabolic reaction increases but generation time reduces
• Vibrio parahaemolyticus


  • Can divide every 10-12 minutes @ 37°C
• Pyrococcus furiosus


  • Can divide every 37 minutes @ 100°C
• Stationary phase


  • No growth
  • Nutrient is exhausted; toxic by-products accumulate
  • Cells entering stationary phase do not simply shut down but undergo some changes like synthesis of new starvation-specific proteins for survival
• Death or decline phase


  • As the culture medium accumulates toxic waste and nutrients are exhausted, cells die in greater number than the dividing cells
• Ultramicrobacteria

  Majority of marine bacteria in the open sea are very small, 0.3 m in diameter, due to their genetically fixed phenotype or as a result of physiological changes associated with starvation
• Cell viability


  • Can be measured using different fluorochromes (dye)
  • Can be counted directly using epifluorescence microscopy or flow cytometry
  • Can be measured indirectly using plate counting in the laboratory using selective or non-selective media
• Viable but not culturable (VBNC)

  • Not all viable bacterial cells are culturable
  • Examples include gram negative and few gram positive pathogens of humans, fish and invertebrates
  • VBNC state of marine bacteria are very much affected by the amount of nutrients in the environment, temperature, pH, salinity and pressure
• Macronutrients, micronutrients and trace elements needed for bacterial growth

  • Carbon
  • Oxygen
  • Nitrogen
  • Sulfur
  • Phosphorus
  • Potassium
  • Calcium
  • Magnesium
  • Iron
  • Manganese
  • Cobalt
  • Zinc
  • Molybdenum
  • Copper
  • Nickel
  • Amino acids
  • Pyrimidines
  • Purines
  • Vitamins
• Sodium requirement for 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 of 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 optima of 20-35°C
• Colwellia psychroerythrea

  • An obligate psychrophile that is widely distributed in Antarctic and Arctic regions, recently became the first cold-adapted organism
• Thermophilic prokaryotes

  • Found in hydrothermal vents, abyssal hot vents and active volcanic seamounts
• Hyperthermophiles

  • Organisms that can grow above 80°C, majority belong to Archaea domain while 2 species belong to Bacteria
• Barotolerant bacteria and archaea

  • Can grow from 1-400 atm but have low metabolic and growth rate
• Obligate or extreme barophiles

  • Organisms which can grow above 400 atm
• Categories of microbes 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 formed in the sheath of some Cyanobacteria
• UV resistance mechanisms in some coral-associated bacteria

  • Enhancing the activity of NAD(P)H quinone oxidoreductase, a powerful antioxidative enzyme
• Extreme halophiles

  • Several genera of Archaea can grow at very high NaCl concentrations (15–35%) found in salterns, submarine brine pools and brine pockets within sea ice
  • Extreme halophilicity is rare in the Bacteria, but Salinibacter rubrum is an exception
• Adaptations to extreme salinity

  • Organisms would synthesize some chemicals to prevent water loss or develop some mechanisms
• Major divisions of the ocean

  • Pelagic
  • Benthic
• Pelagic provinces


  • Neritic
  • Oceanic
• Ocean zones

  • Epipelagic (photic) zone (0-200 m)
  • Mesopelagic (twilight) zone (200-1000 m)
  • Bathypelagic (aphotic) zone (1000-4000 m)
  • Abyssopelagic zone (4000-6000 m)
  • Hadopelagic zone (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
  • Can form through abiotic processes or contain active complex assemblages of bacteria and bacterivorous protists
  • Aggregates grow over time and may reach several centimeters in diameter, traveling for weeks before reaching the ocean floor
  • Deep-sea organisms rely heavily on marine snow as an energy source
• Types of marine sediments

  • Continental transport and sedimentation of biological products
  • Salt marshes
  • Mangroves
  • Coral reefs
• Biofilms


  Consist of a collection of microbes bound to a surface
• Microbial mats


  Consist of 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