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The Biogeochemical Cycles
Nitrogen Cycle
Nitrogen
Nitrogen-one of the most essential
elements-used to produce a number of
complex molecules like amino acids, nucleic acids
and lipids- covers 78% of the earth
atmosphere-cannot be used by most of
the living organisms until fixed
Amino acidsNH
4+
Ammonium
SYNTHESIS
AMMONIFICATION
Nitrogen
FIXATIONN
2AtmosphericNitrog
en
NH3Ammonia
Nitrogen Cycle
Nitrogen Cycle-the movement of nitrogen
between the earth and the atmosphere
-consists of a series of processes that convert nitrogen
gas to organic substances and these back to nitrogen in nature
- nitrogen cycle can be broken down into five types of reactions
Anammox
Reactions of Nitrogen Cycle
•Nitrogen fixation•Ammonification•Nitrification•Denitrification•Anammox
Nitrogen Fixation
Nitrogen Fixation
-reduction of atmospheric nitrogen to ammonia
-requires alot of energy to break the N2 bond
N2
AtmosphericNitrog
en
FIXATION
NH3Ammonia
Nitrogen Fixation
Ways to Fix Nitrogen1.Atmospheric Fixation- using
enormous energy of lightning to break nitrogen molecules
2.Industrial Fixation- use of atmospheric nitrogen and hydrogen as a catalyst under a great temperature(600°C)
3.Biological Fixation- fixation of nitrogen-fixing bacteria
Nitrogen Fixation
Nitrogen-Fixing Bacterias-contain an enzyme complex
called nitrogenase- use at least 16 ATP on each
N2
Nitrogenase-catalyst in the nitrogen-
fixation-it supplies oxygen and ATP -consists of two distinct
proteins, dinitrogenase and dinitrogenase reductase
Nitrogen Cycle
Free living Symbiotic with plants
Aerobic Anaerobic Legumes
Other plants
AzotobacterBeijerinckiaKlebsiella (s
ome)Cyanobacteria (some)*
Clostridium (some)
DesulfovibrioPurple sulphur
bacteria*Purple non-
sulphur bacteria*
Green sulphur
bacteria*
Rhizobium
FrankiaAzospiri
llum
Examples of nitrogen-fixing bacteria (*photosynthetic bacterium)
*Examples of nitrogen-fixing bacteria (*photosynthetic bacterium)
Red nitrogen-fixing nodules on the roots of a black alder tree. The nodules contain symbiotic Frankia sp. bacteria
Nodules on the roots of soybean plants containing Rhizobium sp. bacteria
Desulfovibrio vulgaris
Desulfovibrio sapovorans
Desulfovibrio desulfuricans
Ammonification
Ammonification-decomposition process that
converts organic nitrogen into ammonia (NH3) or ammonium in neutral environment
-performed by a large variety of organism, aerobes and anaerobes as well as fungi(decomposers)
Ammonification
Ammonification Process1. Initially done through the
action of extracellular proteolytic enzymes
2. The breakdown products goes into the cell
3. Release of ammonium
Streptomyces coelicolor colonies
Bacillus cereus colonies on sheep blood agar plate
Nitrification
Nitrification-oxidation of ammonia or ammonium to nitrate-done by a group of bacteria collectively known as nitrifiers-a cooperative two-step process
Nitrification
Nitrification Process1. Nitrosomonas (ammonia-
oxidizing bacteria), oxidizes ammonia to nitrite(Nitritation)
2. Nitrospira (nitrite-oxidizing bacteria) oxidizes nitrite to nitrate (Nitratation)
NITRITATION
NITRATATION
NH3Ammo
nia
NO2
-Nitrite
NO3
-Nitrate
Nitrosomonas sp. bacteriaUptake of Pyruvate by
Nitrosomonas(green) and Nitrospira(red). Taken via microautoradiography
Denitrification
Denitrification-conversion of nitrates into
primarily nitrogen gas but also nitrous oxide
-done by denitrifying bacteriasNO3
-Nitrate
N2
ONitrou
s Oxide
N2Atmospheric Nitrog
en
NITRITATION +
Denitrification
Environmental Consequences of Denitrification
-N2O can be photochemically oxidized to NO in the atmosphere. NO reacts with the ozone (O3) in the to form nitrite (NO2
-), and this returns to Earth as nitric acid (HNO2).
thinning of ozone layerformation of acid rain
Pseudomonas aeruginosa (XLD)Xylose lysine deoxycholate agar plate
Paracoccus denitrificans
Annamox
Annamox-oxidation of ammonium
under anaerobic conditions to form atmospheric nitrogen(N2)
-bacteria capable of this process possess a special membrane-bound organelle called annamoxosomes
NH4
+Ammonium
2H2
Owater
N2Atmospheric Nitrog
en
ANNAMOX ++N
O2-Nitrate
Groups of annamox bacteria
•Brocadia•Kuenenia•Anammoxoglobus• Jettenia (all fresh water species)
•Scalindua(marine species)
Reaction
Microorganism
Conditions
Process
Nitrogen fixation
Nitrogen-fixing bacteria e.g. Rhizobium
Aerobic/anaerobic
The first step in the synthesis of virtually all nitrogenous compounds. Nitrogen gas is fixed into forms other organisms can use.
Ammonification(decay)
Ammonifying bacteria (decomposers)
Aerobic/anaerobic
The decomposers, certain soil bacteria and fungi, break down proteins in dead organisms and animal wastes, releasing ammonium ions which can be converted to other nitrogen compounds.
Nitrification
Nitrifying bacteria (e.g. Nitrosomonas, Nitrobacter)
Aerobic Nitrification Nitrifying bacteria Aerobic Nitrification is a two-step process. Ammonia or ammonium ions are oxidized first to nitrites and then to nitrates, which is the form most usable by plants.
Denitrification
Denitrifying bacteria
Anaerobic
Nitrates are reduced to nitrogen gas, returning nitrogen to the air and completing the cycle.
Annamox
Bacterias with annamoxosomes
Anaerobic
Ammonium ions are oxidize to nitrogen gas, thus returning the nitrogen in the atmosphere
Anammox