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Mikrob bermanfaat1
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MIKROORGANISME YANG
BERMANFAAT
BIOTEKNOLOGI PERTANIAN
MAGISTER PERTANIAN, FAK. PERTANIAN, UKSW
DEFINISI
Mikroorganisme yang berperan menyehatkan atau membuat /menjaga kondisi tanah tetap sehat sehingga pertumbuhan & kesehatan tanaman tetap terjaga
WHY IS IMPORTANT
Keberadaan dan aktivitas mikroorganisme ini mempengaruhi
kualitas tanah,
produktivitas tanaman, dan
kesehatan tanaman.
Soil Environments
Surface and subsurface soils are typically nutrient-poor environments for microbes
Rhizosphere is enriched in nutrients as a result of nearby plant activities
Rhizosphere
Rhizoplane
soil in direct contact with plant root
Endophytes
microbes attached to root surface
Decreasing moisture Increasing organic C
Organic material in rhizosphere Exudates
low molecular weight compounds released from plant cells in a non-metabolic manner (leakage)
Secretions
compounds metabolically released from plant cells
Lysates
compounds released from moribund cells during autolysis
Plant mucilage
plant polysacchrides
Densities of microorganisms in rhizosphere
Decreasing microbial diversity
Beneficial root-microbe interactions
Atmosphere contains 1015 tons N2 gas
Biological nitrogen fixation
Minimum of 70 million tons N fixed/year
Sources of Fixed Nitrogen
65%10%
25%
Biological Lightning Fertilizer
Functions of beneficial microorganisms
Functions of Microorganisms: Putrefaction, Fermentation, and Synthesis
Fermentation : an anaerobic process by which facultative microorganisms (e.g., yeasts) transform complex organic molecules (e.g., carbohydrates) into simple organic compounds that often can be absorbed directly by plants.
Fermentation yields a relatively small amount of energy compared with aerobic decomposition of the same substrate by the same group of microorganisms.
Aerobic decomposition results in complete oxidation of a substrate and the release of large amounts of energy, gas, and heat with carbon dioxide and water as the end products.
Putrefaction is the process by which facultative heterotrophic microorganisms decompose proteins anaerobically, yielding mal odorous incompletely oxidized, metabolites (e.g., ammonia, mercaptans and indole) that are often toxic to plants and animals.
Synthetic" microorganisms:
the term "synthesis used here refers to the biosynthetic capacity of certain microorganisms to derive metabolic energy by "fixing" atmospheric nitrogen and/or carbon dioxide.
If they should become a predominant part of the soil microflora, then the soil would be termed a "synthetic" soil.
1. NITROGEN FIXATION
Symbiotic Relationships
Both host and parasite benefit
Ex. Rhizobia (Symbiont) and Legumes (Host)
Rhizobia: sugars, proteins, and oxygen
Plant: usable nitrogen
Legumes
Preserve the nitrogen balance in the soil
Two Types
Legumes
Non-Legume
Release flavonoids
Importance of legume-rhizobia
symbiosis
Symbiotic N-fixation
Relationship Symbiont/Microbe Host/Crop
Symbiotic Bacteria (Rhizobia) Legumes
Actinomycete (Frankia) Non-legumes
Cyanobacteria (Anabaena) Azolla (fern)
Associative Bacteria
Acetobacter Sugarcane
Azotobacter Tropical grasses
Azospirillum Tropical grasses
Beneficial root-microbe interactions
Beneficial root-microbe interactions
Biological nitrogen fixation
N2 + 3H2 2NH3
Root Nodule Initiation
Two types of Nodule
Effective
Ineffective
Two groups of Genes Necessary
Common Nodulation Genes (nodABCD)
nodD only gene expressed in absence of a suitable host
Host Specific Nodulation Genes
Root Nodule Initiation Legumes release flavonoids
Triggers production of Nod Factors (Lipochito-oligosaccharide) by bacteria
Flavonoids interact with nodD product
Expression of nodABC genes
Plant-rhizobia genetic interactions
Poly-N-acetyl-glucosamine
Root Nodule Development
Nod factor sensed by root
Cell division occurs
Rhizobia attach within minutes
Root hair curling begins
Rhizobia travel along an infection thread
As infection thread penetrates the root cortex, Rhizobia are released
Nodule initiation and development
Nodule initiation and development
Root Nodule Function
Nodule forms 1 to 2 weeks after infection
Two types of Nodules
Determinate
Indeterminate
Rhizobia enlarge approx. 5 times
Change physiologically to form bacteroids
Root Nodule Fixation
Nodulins produced during maturation include: Leghemoglobin (protects
nitrogenase enzyme),
Nitrogenase, and
Glutamine synthetase
Fixation usually occurs after about 15 days
Root Nodule Fixation
Indeterminate
Fixation: ammonia
Exported: asparagine
Determinate
Fixation: ammonia
Exported: purine
Enhancing the Symbiosis
Natural symbiosis is reasonably effective Free-living nitrogen fixation
gives 25kg/hectare/year
Symbiotic nitrogen fixation gives 100kg/hectare/crop
Enhancing the Symbiosis
Current enhancements Application of rhizobial inoculants
(biofertiliser) Peat-based carrier with 109
rhizobia/gram of peat Application directly to seeds, then
planting
Application to seed furrow
Crop rotation/breeding
Tahapan pemanfaatan mikroba penambat N
Isolasi:
Medium & metode isolasi yang digunakan tergantung jenis mikroba yang akan diisolasi
Ex. Rhizobium: med YEMA, nodul akar/batang simbiosis
Azospirillum: med semi padat asam malat, rhizosfer padi-padian/jagung asosiatif
Azotobacter: med Jensen/Ashby, sampel tanah hidup bebas
Metode isolasi untuk mikrob simbiosis
Pengayaan dengan menggunakan sumber akar legum
Medium selektif dan diferensial YEMA (yeast extract manitol agar) dapat membedakan anggota Rhizobiaceae (Agrobacterium dan Rhizobium)
Agrobacterium merah, Rhizobium pink
Metode isolasi untuk mikrob asosiatif
Pengayaan dengan menggunakan sumber akar gramineae
Medium selektif medium mengandung sumber C malat & soft (lunak) yang dapat menggunakan malat hanya kelompok spirillum & tumbuh di bawah permukaan (mikroaerofil)
Metode isolasi untuk mikrob hidup bebas
Pengayaan dengan menggunakan sumber tanah rhizosfir
Media yang digunakan adalah medium spesifik dan selektif
Perlu uji postulat Koch
Pengujian kemampuan:
Tergantung mikroba yang diuji, ex. untuk Rhizobium dapat menggunakan tabung atau pot
Tahapan pemanfaatan mikroba penambat N
Tahapan pemanfaatan mikroba penambat N
Tahapan pemanfaatan mikroba penambat N
Tahapan pemanfaatan mikroba penambat N
Identifikasi
Pemeliharaan & perbanyakan:
Pemeliharaan dapat menggunakan media agar miring atau lyofilisasi
Tahapan pemanfaatan mikroba penambat N
Perbanyakan dilakukan menggunakan bioreaktor/fermenter umumnya dengan sistem curah (batch)
Tahapan pemanfaatan mikroba penambat N
Tahapan pemanfaatan mikroba penambat N
Formulasi produk:
Menggunakan carrier inoculant, misalkan gambut atau pupuk kandang/kotoran ternak.