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

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.

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)

Earth’s ecosystems are maintained by a constant influx of energy Transformation Loss of Energy Solar Energy Autotroph Herbivore Carnivore Respiratory Loss

Biogeochemical Cycles Cycling of chemical elements between living and non- living 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. Over the past three decades, considerable understanding has been accumulated about the patterns and magnitudes of the circulation of these critical elements. Humans are altering these cycles and it is essential to understand the changes induced by anthropogenic activity.

Siklus N

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 amoniak.

Surface water Low [NH4] Oxidized layer Biodegradation Reduced soil layer Slow Diffusion C/N <20 C/N >20 [NH4] HIGH

Surface water nitrification Low [NH4] Oxidized layer [NO3] high Reduced soil layer Slow Diffusion [NH4] HIGH

N2 Surface water Oxidized layer [NO3] high Leaching Reduced soil layer [NO3] Low Denitrification

Nitrogen Fixation Nodules on plant roots

Reaksi-reaksi dalam Siklus Nitrogen

Sumber N Lightning Inorganic fertilizers Nitrogen Fixation Animal Residues Crop residues Organic fertilizers

Forms of Nitrogen Roles of Nitrogen Urea  CO(NH2)2 Ammonia  NH3 (gaseous) Ammonium  NH4 Nitrate  NO3 Nitrite  NO2 Atmospheric Dinitrogen N2 Organic N 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.

Global Nitrogen Reservoirs Metric tons nitrogen Actively cycled Atmosphere 3.9*1015 No Ocean  soluble salts Biomass 6.9*1011 5.2*108 Yes Land  organic matter  Biota 1.1*1011 2.5*1010 Slow

Nitrogen is a key element for amino acids nucleic acids (purine, pyrimidine) cell wall components of bacteria (NAM).

Nitrogen Cycles Ammonification/mineralization Immobilization Nitrogen Fixation Nitrification Denitrification

R-NH2 NH4 NO2 NO3 NO N2O N2

Ammonification or Mineralization NH4 NO2 R-NH2 NO NO2 NO3

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

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

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) R-NH2 NH4 NO2 NO3 NO N2O N2

Microorganisms fixing Azobacter Beijerinckia Azospirillum Clostridium Cyanobacteria Require the enzyme nitrogenase Inhibited by oxygen Inhibited by ammonia (end product) Anabaena Microcystis

Rates of Nitrogen Fixation N2 fixing system Nitrogen Fixation (kg N/hect/year) Rhizobium-legume 200-300 Cyanobacteria- moss 30-40 Rhizosphere associations 2-25 Free- living 1-2

Bacterial Fixation Occurs mostly in salt marshes Is absent from low pH peat of northern bogs Cyanobacteria found in waterlogged soils

Nitrification Two step reactions that occur together : 1rst step catalyzed by Nitrosomonas 2 NH4+ + 3 O2  2 NO2- +2 H2O+ 4 H+ 2nd step catalyzed by Nitrobacter 2 NO2- + O2  2 NO3- R-NH2 NH4 NO2 NO3 NO N2O N2 Optimal pH is between 6.6-8.0 If pH < 6.0  rate is slowed If pH < 4.5  reaction is inhibited

Denitrifikasi Removes a limiting nutrient from the environment R-NH2 NH4 NO2 NO3 NO N2O N2 Removes a limiting nutrient from the environment 4NO3- + C6H12O6 2N2 + 6 H20 Inhibited by O2 Not inhibited by ammonia Microbial reaction Nitrate is the terminal electron acceptor

Interactive Nitrogen Cycle N2 Fixation Plant and Animal Residues Industrial Processes Fertilizer Lightning, Rainfall Atmosphere Organic Matter Volatilization Leaching N2, N2O, NO R-NH2 + Energy + CO2 R-NH2 + H2O R-OH + Energy + 2NH3 Soil exchange sites 2NH4+ + 2OH- 2NO2- + H2O + 4H+ NO3- Pool Plant/Microbial Sink Plant Loss Back to Intro Page

Back to Intro Page OXIDATION STATES ORGANIC MATTER PLANT AND ANIMAL MESQUITE RHIZOBIUM ALFALFA SOYBEAN BLUE-GREEN ALGAE AZOTOBACTER CLOSTRIDIUM PLANT AND ANIMAL RESIDUES R-NH2 + ENERGY + CO2 R-NH2 + H2O R-OH + ENERGY + 2NH3 MATERIALS WITH N CONTENT < 1.5% (WHEAT STRAW) CONTENT > 1.5% (COW MANURE) MICROBIAL DECOMPOSITION HETEROTROPHIC AMINIZATION BACTERIA (pH>6.0) FUNGI (pH<6.0) AMMONIFICATION GLOBAL WARMING pH>7.0 2NH4+ + 2OH- FIXED ON EXCHANGE SITES +O2 Nitrosomonas 2NO2- + H2O + 4H+ IMMOBILIZATION NH3 AMMONIA -3 NH4+ AMMONIUM -3 N2 DIATOMIC N 0 N2O NITROUS OXIDE 1 NO NITRIC OXIDE 2 NO2- NITRITE 3 NO3- NITRATE 5 OXIDATION STATES ATMOSPHERE N2O NO N2 N2O2- NH3 SYMBIOTIC NON-SYMBIOTIC + O2 Nitrobacter FERTILIZATION LIGHTNING, RAINFALL N2 FIXATION DENITRIFICATION PLANT LOSS AMINO ACIDS NO3- POOL LEACHING AMMONIA VOLATILIZATION NITRIFICATION NH2OH Pseudomonas, Bacillus, Thiobacillus Denitrificans, and T. thioparus MINERALIZATION + NITRIFICATION NO2- MICROBIAL/PLANT SINK TEMP 50°F pH 7.0 ADDITIONS LOSSES OXIDATION REACTIONS REDUCTION REACTIONS HABER BOSCH 3H2 + N2 2NH3 (1200°C, 500 atm) Joanne LaRuffa Robert Mullen Wade Thomason Susan Mullins Shannon Taylor Heather Lees Department of Plant and Soil Sciences Oklahoma State University INDUSTRIAL FIXATION

Siklus Oksigen

O2 + carbohydrates → CO2 + H2O + energy 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

Siklus P

Siklus P di Lautan

Siklus P di dalam Tanah

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.

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.

Siklus Karbon

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.

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 carbon- carbon 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.

Carbon is readily exchanged between the atmosphere and ocean 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−