MIKROORGANISME DALAM
SIKLUS BIOGEOKIMIA
Oleh: Dr. Ratu Safitri, MS
Laboratorium Mikrobiologi. Jurusan Biologi F-MIPA
Universitas Padjadjaran
LINGKUP MATERI:
 Ikhtisar
Siklus Biogeokimia :
- Siklus N dan Reaksi dalam siklus
- Siklus O
- Siklus P
- Siklus C
2
DASAR DARI KONSEP SIKLUS
BIOGEOKIMIA
 Semua
materi siklus tidak diciptakan atau
dihancurkan


Sehubungan karena bumi adalah suatu
sistem tertutup, maka semua hal yang berada
di dalamya akan dalam suatu siklus.
Siklus Biogeokimia: perbahan atau sklus
materi dalam suatu sistem lingkungan.
3
JENIS MATERI YANG BEREDAR



Element kimia (carbon, nitrogen, oxygen, sulfur ,
Phosphor) atau molekule air .
Makronutient : diperlukan pertukaran dalam
jumlah yang besar, misal : potassium , calcium ,
iron , magnesium
Mikronutrien beredar dalam jumlah yang
sangat kecil, misalnya: boron (tanaman hijau)
copper (untuk aktifitas ensim)
molybdenum (nitrogen-fixing bacteria)
4
-
EARTH’S ECOSYSTEMS ARE MAINTAINED
BY A CONSTANT INFLUX OF ENERGY
Transformation Loss of Energy
Solar
Energy
Autotroph
Herbivore
Respiratory Loss
Carnivore
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BIOGEOCHEMICAL CYCLES
Cycling of chemical elements
between living and nonliving portions of the earth’s
ecosystems
Decomposition
Respiration
Excretion
Biotic
Uptake
Abiotic
BIOGEOCHEMICAL CYCLE:
Siklus utama yang akan dibahas:
 Siklus nitrogen
 Siklus oxygen
 Siklus phosphorus
 Siklus carbon
Sirkulasi molekul kimia dalam siklus biogeokimia dan
interaksinya dalam siklus adlah sangat penting untuk
memelihara ekosistem terestrial, air tawar, dan
ekosistem laut. Perubahan iklim global, temperatur,
hujan, dann kestabilan ekosistem sangat tergantung
pada siklus biogeokimia.
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Siklus N
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NITROGEN BEREDAR DI TANAH
-Komposisi N udara: 80%
- Nitrogen beredar dalam
peredaran :
(a). Bakteri dalam tanah
akan merubah nitrat menjadi gas ke
udara (denitrifikasi)
(b) Dengan adanya cahaya, sejumlah
nitrogen dioksidasi dan bergabung
dengan air membentuk asam dan
akan jatuh dalam bentuk hujan.
•Tanaman akan mengambil nitrat dan mengubahnya menjadi bahan protein
yang akan diantarkan oleh karnivora dan herbivora dalam rantai makanan.
•Ketika organisma mengelurakan limbah, nitrogen akan dikembalikan ke
lingkunga. Ketika biota mati, akan didekomposisi dan dikonversikan menajdi 9
amoniak.
10
11
Surface
water
Oxidized
layer
Reduced
soil layer
Low [NH4]
Biodegradation
Slow Diffusion
C/N <20
C/N >20
[NH4] HIGH
12
Surface
water
Oxidized
layer
Reduced
soil layer
nitrification
Low [NH4]
[NO3] high
Slow Diffusion
[NH4] HIGH
13
N2
Surface
water
Oxidized
layer
Reduced
soil layer
[NO3] high
Leaching
[NO3] Low
Denitrification
14
Nitrogen Fixation
15
Nodules on plant roots
REAKSI-REAKSI DALAM
SIKLUS NITROGEN
SUMBER N
Lightning
 Inorganic
fertilizers
 Nitrogen Fixation
 Animal Residues
 Crop residues
 Organic fertilizers

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FORMS OF NITROGEN
Urea  CO(NH2)2
 Ammonia  NH3 (gaseous)
 Ammonium  NH4
 Nitrate  NO3
 Nitrite  NO2
 Atmospheric Dinitrogen N2
 Organic N

ROLES OF NITROGEN
Plants and bacteria use
nitrogen in the form of
NH4+ or NO3 It serves as an electron
acceptor in anaerobic
environment
 Nitrogen is often the most
limiting nutrient in soil and
water.

18
GLOBAL NITROGEN RESERVOIRS
Nitrogen
Reservoir
Atmosphere
Metric tons
nitrogen
3.9*1015
Actively cycled
Ocean 
soluble salts
Biomass
6.9*1011
5.2*108
Yes
Yes
Land  organic
matter
 Biota
1.1*1011
2.5*1010
Slow
Yes
No
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NITROGEN IS A KEY
ELEMENT FOR
amino acids
 nucleic acids (purine,
pyrimidine)
 cell wall components of
bacteria (NAM).

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NITROGEN CYCLES
Ammonification/mineralization
 Immobilization
 Nitrogen Fixation
 Nitrification
 Denitrification

21
N2
N2O
NH4
NO2
R-NH2
NO
NO2
NO3
22
AMMONIFICATION OR MINERALIZATION
N2
N2O
NH4
NO2
R-NH2
NO
NO2
NO3
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MINERALIZATION OR AMMONIFICATION








Decomposers: earthworms, termites, slugs, snails, bacteria,
and fungi
Uses extracellular enzymes  initiate degradation of plant
polymers
Microorganisms uses:
Proteases, lysozymes, nucleases to degrade nitrogen
containing molecules
Plants die or bacterial cells lyse  release of organic nitrogen
Organic nitrogen is converted to inorganic nitrogen (NH3)
When pH<7.5, converted rapidly to NH4
Example: Urea
NH3 + 2 CO2
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IMMOBILIZATION
 The
opposite of mineralization
 Happens when nitrogen is limiting in the
environment
 Nitrogen limitation is governed by C/N ratio
 C/N typical for soil microbial biomass is 20
 C/N < 20 Mineralization
 C/N > 20 Immobilization
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NITROGEN FIXATION

Energy intensive process :

N2 + 8H+ + 8e- + 16 ATP = 2NH3 + H2 + 16ADP + 16 Pi
Performed only by selected bacteria and actinomycetes
 Performed in nitrogen fixing crops
(ex: soybeans)
N

2
N2O
NH4
NO2
R-NH2
NO
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NO2
NO3
MICROORGANISMS FIXING
Azobacter
 Beijerinckia
 Azospirillum
 Clostridium
 Cyanobacteria

Anabaena
Require the enzyme
nitrogenase
 Inhibited by oxygen
 Inhibited by ammonia
(end product)

Microcystis
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RATES OF NITROGEN FIXATION
N2 fixing system
Rhizobium-legume
Nitrogen Fixation (kg
N/hect/year)
200-300
Cyanobacteria- moss
30-40
Rhizosphere
associations
Free- living
2-25
1-2
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BACTERIAL FIXATION
Occurs mostly in salt marshes
 Is absent from low pH peat of northern bogs
 Cyanobacteria found in waterlogged soils

29
NITRIFICATION
Two step reactions that occur together :
 1rst step catalyzed by Nitrosomonas
2 NH4+ + 3 O2  2 NO2- +2 H2O+ 4 H+
N2


2nd step catalyzed by Nitrobacter
2 NO2- + O2  2 NO3-

Optimal pH is between 6.6-8.0

If pH < 6.0  rate is slowed

If pH < 4.5  reaction is inhibited
N2
O
N
H4
NO
2
RNH2
N
O
NO2
NO
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3
DENITRIFIKASI
N2
Removes a limiting
nutrient from the
environment
 4NO3 + C6H12O6 2N2
+ 6 H 20
 Inhibited by O2
 Not inhibited by
ammonia
 Microbial reaction
 Nitrate is the terminal
electron acceptor

N2
O
NH
NO2
4
R-NH2
NO
NO2
NO3
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Interactive Nitrogen Cycle
Atmosphe
re
N2
Fixation
Industria
l
Process
es
Plant and
Animal
Residues
Lightning
, Rainfall
Fertilizer
Pla
nt
Los
s
Volatilizati
on
R-NH2 + Energy +
CO2
Organic
Matter
N2, N2O,
NO
R-NH2 +
H2O
Plant/Micro
bial Sink
NO3Pool
R-OH + Energy +
2NH3
Soil exchange
sites
2NH4+ +
2OH-
32
Leachin
g
2NO2- + H2O +
4H+
Back to
Intro
Page
Back to
Intro Page
GLOBAL WARMING
ATMOSPHERE
N2O
NO
N2
PLANT
LOSS
INDUSTRIAL
FIXATION
N2 FIXATION
SYMBIOTIC
NON-SYMBIOTIC
MESQUITE
RHIZOBIUM
ALFALFA
SOYBEAN
BLUE-GREEN ALGAE
AZOTOBACTER
CLOSTRIDIUM
LIGHTNING,
RAINFALL
PLANT AND ANIMAL
RESIDUES
HABER BOSCH
(1200°C, 500 atm)
3H2 + N2
2NH3
MATERIALS WITH N
CONTENT > 1.5%
(COW MANURE)
FERTILIZATION
MATERIALS WITH N
CONTENT < 1.5%
(WHEAT STRAW)
AMINO
ACIDS
NH3
AMMONIA
VOLATILIZATION
AMINIZATION
ORGANIC
MATTER
HETEROTROPHIC
R-NH2 + ENERGY + CO2
BACTERIA (pH>6.0)
FUNGI (pH<6.0)
IMMOBILIZATION
Pseudomonas, Bacillus,
Thiobacillus Denitrificans,
and T. thioparus
R-OH + ENERGY + 2NH3
N2O2MINERALIZATION
+ NITRIFICATION
MICROBIAL/PLANT
SINK
2NH4+ + 2OHFIXED ON
EXCHANGE
SITES
NO2-
OXIDATION STATES
NH3 AMMONIA
-3
NH4+ AMMONIUM
-3
N2 DIATOMIC N
0
N2O NITROUS OXIDE 1
NO NITRIC OXIDE
2
NO2- NITRITE
3
NO3 NITRATE
5
pH>7.0
R-NH2 + H2O
AMMONIFICATION
NH2OH
NO3POOL
DENITRIFICATION
LEACHING
TEMP 50°F
LEACHING
NITRIFICATION
2NO2- + H2O + 4H+
Nitrobacter
LEACHING
VOLATILIZATION
NITRIFICATION
LEACHING
+ O2
Joanne LaRuffa Robert Mullen
Wade Thomason Susan Mullins
Shannon Taylor
Heather Lees
LEACHING
pH 7.0
+O2
Department of Plant and Soil Sciences
Oklahoma State University
ADDITIONS
LOSSES
33
OXIDATION REACTIONS
REDUCTION REACTIONS
SIKLUS OKSIGEN
34
Tanaman menggunakan energi matahari untuk
mengkonversikan karbondioksida dan air menjadi
karbohidrat dan oksigen melalui fotositesis.
6CO2 + 6H2O + energy → C6H12O6 + 6O2

Organisma fotosintetik berperan dalam siklus
oksigen termasuk tanaman , phytoplankton di laut.
Biota laut cyanobacteria Prochlorococcus ditemukan
tahun 1986.
 Hwan membentuk setengah siklus dari oksigen yang
digunakan untuk memecah karbohidrat menjadi
energi dalam proses respirasi.
O2 + carbohydrates → CO2 + H2O + energy

35
SIKLUS P
36
SIKLUS P DI LAUTAN
37
SIKLUS P DI DALAM TANAH
38
The phosphorus cycle describes the movement of
phosphorus through the lithosphere, hydrosphere, and
biosphere. The atmosphere does not play a significant
role, because phosphorus and phosphorus-based
compounds are usually solids at the typical ranges of
temperature and pressure found on Earth.
 Phosphorus normally occurs in nature as part of a
phosphate ion, consisting of a phosphorus atom and
some number of oxygen atoms, the most abundant
form (called orthophosphate) having four oxygens:
PO43-. Most phosphates are found as salts in ocean
sediments or in rocks. Over time, geologic processes
can bring ocean sediments to land, and weathering will
carry terrestrial phosphates back to the ocean.

39
Plants absorb phosphates from the soil and phosphate
enters the food chain. After death, the animal or plant
decays, and the phosphates are returned to the soil.
Runoff may carry them back to the ocean or they may
be reincorporated into rock.
 The primary biological importance of phosphates is as
a component of nucleotides, which serve as energy
storage within cells (ATP) or when linked together,
form the nucleic acids DNA and RNA. Phosphorus is
also found in bones, and in phospholipids (found in all
biological membranes).
 Phosphates move quickly through plants and animals;
however, the processes that move them through the
soil or ocean are very slow, making the phosphorus
cycle overall one of the slowest biogeochemical cycles.

40
Siklus Karbon
41
Usually thought of as four major reservoirs of carbon
(the atmosphere, the terrestrial biosphere - which
includes freshwater systems and non-living organic
material, such as soil carbon -, the oceans with
dissolved inorganic carbon and living and non-living
marine biota, and the sediments which includes fossil
fuels) interconnected by pathways of exchange.
 The exchanges between reservoirs, occur because of
various chemical, physical, geological, and biological
processes. The ocean contains the largest active pool of
carbon near the surface of the Earth, but the deep
ocean part of this pool does not rapidly exchange with
the atmosphere.

42
The global carbon budget is the balance of the
exchanges (incomes and losses) of carbon between the
carbon reservoirs or between one specific loop (e.g.,
atmosphere - biosphere) of the carbon cycle.
IN THE OCEAN:
 The seas contain around 36000 gigatonnes of carbon,
mostly in the form of bicarbonate ion. Inorganic
carbon, that is carbon compounds with no carboncarbon or carbon-hydrogen bonds, is important in its
reactions within water. This carbon exchange becomes
important in controlling pH in the ocean and can also
vary as a source or sink for carbon.

43

Carbon is readily exchanged between the atmosphere
and ocean. In regions of oceanic upwelling, carbon is
released to the atmosphere. Conversely, regions of
downwelling transfer carbon (CO2) from the
atmosphere to the ocean. When CO2 enters the ocean,
carbonic acid is formed:


CO2 + H2O ⇌ H2CO3
This reaction has a forward and reverse rate, that is it
achieves a chemical equilibrium. Another reaction
important in controlling oceanic pH levels is the
release of hydrogen ions and bicarbonate. This reaction
controls large changes in pH:

H2CO3 ⇌ H+ + HCO3−
44