BIOL 1111 Lecture Notes - Lecture 5: Facultative Anaerobic Organism, Nitrification, Nitrogen Cycle
13 Jun 2018
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Prokaryotes and Oxygen
Aerobes: require oxygen for cellular respiration; oxygen is final electron acceptor
Obligate aerobes: cannot survive without oxygen
Anaerobes: do not require oxygen to live
Obligate anaerobes: cannot survive with oxygen
-use fermentation: respiration in which inorganic molecules (NO3– or SO42–) are the final electron
acceptor
Facultative anaerobes: Use oxygen when present; use fermentation under anaerobic conditions
Prokaryotes and Biogeochemical Cycles
Biogeochemical Cycle: pathway by which a chemical element is recycled through an ecosystem
Nitrogen Cycle: most nitrogen is N2; prokaryotes can break the triple bond
**nitrogen is the backbone of peptides and important for the formation of nucleic acids
Nitrogen Fixation
-Conversion of atmospheric nitrogen (N2) to ammonia (NH3) (using nitrogenase to catalyze 3 covalent
bonds)
-Ammonia ionized to ammonium (NH4+) for biosynthesis aoiu is’t useful i this for, so it goes
on through to undergo nitrification)
-ex. Cyanobacteria, Rhizobium
Nitrification
-Conversion of ammonium (NH4+) to nitrate (NO3–)
-two step conversion by 2 types of bacteria
1. Some bacteria convert ammonium to nitrite (NO2–)
2. Other bacteria convert nitrite to nitrate (NO3–)
-nitrate is used by plants/fungi to build proteins and nucleic acids
Prokaryotic Reproduction
Binary fission
-asexual reproduction
-produces exact copies of parent; can result in rapid population growth
-short generation time plus small genome, which results in high mutation rate, high biodiversity and
high aility to adapt eause they’re sall, whe a utatio ours, rate of utatio is high, ad
therefore have a better ability to adapting to changing environments and have a high biodiversity and
that is why they have survived for so long= evolutionary success)
Mechanisms of Pathogenic Bacteria
1. Exotoxins: toxic proteins released into environment
-ex. C. botulinum (botulism exotoxin), used in botox to temporarily paralyze the muscles injected
2. Endotoxins: associated with cell and are only released when membrane breaks apart (bacteria dies)
-natural component of outer membrane in gram negative bacteria
-ex. E. coli, salmonella, shigella
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