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