Mikrob bermanfaat1

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


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

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



Identifikasi

Pemeliharaan & perbanyakan:

Pemeliharaan dapat menggunakan media agar miring atau lyofilisasi


Perbanyakan dilakukan menggunakan bioreaktor/fermenter umumnya dengan sistem curah (batch)


Formulasi produk:

Menggunakan carrier inoculant, misalkan gambut atau pupuk kandang/kotoran ternak.

Mikrob bermanfaat1

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