Download MIKROBIOLOGI TE RAPAN

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TAKRIF (DEFINITION):
Takrif Biofertilizers
Preparations containing LIVE or LATENT CELLS of
EFFICIENT strains of N2 FIXING, PHOSPHATE
SOLUBILIZING or CELLULOLITIC microorganisms used for
applications to SEED, SOIL or COMPOSTING AREAS, with
the OBJECTIVE of INCREASING THE NUMBERS of such
microorganisms and ACCELERATE certain microbial
PROCESSES to augment the extent of the AVAILABILITY of
nutrients in a form which can be easily assimilated by plant
(Subba Rao,NS “Biofertilizers in Agriculture” Oxford & IBH Publishing Company)
Pupu
k
Haya
ti vs
Pupu
k
Orga
nik
Pupuk dengan bahan aktif
Mikroba Terpilih
Pupuk yang berasal dari sisa-sisa
tumbuhan & atau hewan dalam
berbagai tingkat dekomposisi
Nitrogen Cycle
• The 2 major processes of N2 transformation are:
• Nitrification:
 NH4+ → NO3- :
 NH4+ →NO2 NO2- → NO3-
• By bacteria e.g. Nitrobacter, Bacillus, Paracoccus,
Pseudomonas.
• Denitrification:
– NO3- → N2
• By bacteria e.g. Azotobacter, Clostridium and
Rhizobium.
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Nitrogen Fixation
• N2 is the most stable form of nitrogen and high
energy is required to break the N-N triple bond.
• Therefore only microorganisms can fix nitrogen
• N2 + 8H+ +8e- →2NH3 + H2
• N2 gas is the greatest reserve of nitrogen.
• The productivity of many environs is limited by
the short supply of nitrogenous compounds.
• Nitrogen fixation is important to agriculture and
legumes such as soybean can fix atmospheric
nitrogen.
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Dentrification
• Denitrification is the reduction of nitrates to N2
or NO2.
• This process is detrimental because it removes
nitrogen the environment.
• This is of particular importance to agriculture
where nitrate fertilizers are used.
• If anoxic condition develop e.g. water logged
soil. The nitrate is remove from the soil by
dentrification.
•
What do you unerstand by the term “anoxic conditions”?
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Ammonification
• The decomposition of organic nitrogen
compounds such as amino acids and nucleotides
is called ammonification.
• In the soil much of this NH3 is converted to
amino acids by plants.
• Some NH3 is lost by evaporation especially in
dense animal populations.
• Globally this constitutes 15% of N2 released to
the atmosphere.
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Nitrification
• Nitrification is the oxidation of NH3 to NO3- by nitrifying
bacteria.
• The nitrates produced is readily assimilated by plants.
• Nitrate is soluble and is quickly leached from the soil.
• NH4+ is +vely charged and will adhere to –vely charged
soil (clay) particles.
• NH4+ is extensively used in nitrogenous fertilizers.
• Denitrification consumes N2 while nitrification produces
it.
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3 H2
+
NH3
NH4+
berbentuk kation
 tertahan oleh
partikel tanah yang
bermuatan negatif
 relatif stabil
dalam tanah
NO3berbentuk anion  mobil,
tidak tertahan tanah 
mudah terlindi, runoff, dan
teruapkan dalam bentuk
N2O, NO dan N2 melalui
proses denitrifikasi 
pencemar udara, air tanah
dan perairan
Terjerap mineral lempung tipe 2 : 1
(Vermikulit, Illit, Mica butir halus & Smektit)
NH4+
NO2-
5 ADP
20 ADP
NO3Leaching, Menurunkan kejenuhan
basa & memasamkan tanah,
Pencemaran NO3-, Eutrofikasi,
Nitrosamin, Denitrifikasi
NO3-
Methemoglobinemia
(blue-baby syndrome)
pada Konsumen
(asam hiponitrit)
Nitrogen Fixation by Legumes
• The association of nitrogen fixing bacteria with
legumes is one of the most important bacteria plant
interaction.
• Nitrogen fixing legumes include, soybean, bean, pea,
clover and alfalfa are plants with beans in pods.
• Nitrogen fixing bacteria in plants include:
Rhizobium
Bradyrhizobium
Mesorhizobium
Azorhizobium
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Nitrogen Fixation
• The symbiotic relationship between plant and
nitrogen fixing bacteria results in the
formation of a root nodule.
• In the nodule N2 is converted by the enzyme
nitrogenase to ammonia.
• The ammonia is used in the synthesis of
amino acids and other cellular components.
• Under normal conditions neither Rhizobium
nor the plant can fix nitrogen.
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Root
Nodules
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Nitrogen Fixation
• Rhizobium can only fix N2 under
microaerophilific (reduced O2)
conditions.
• This is because O2 is needed by
Rhizobium but O2 also inhibits
nitrogenase.
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Leghemoglobin
• In the nodule O2 level is reduced by
leghemoglobin.
• Leghemoglobin is synthesized only after
interaction of the plant and Rhizobium.
• 90% of legumes will fix nitrogen.
• However each nitrogen fixing bacteria will
only associate with certain legumes.
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Leghemoglobin
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Steps in Nodule Formation
1. Recognition of the correct partner by both plant and
bacteria.
2. Attachment of the bacteria to the plant root.
3. Invasion of the root hair by bacteria through the
formation of an infection thread.
4. Growth to the main root via the infection thread.
5. Formation of bacteroids (deformed bacteria cells) and
development of nitrogen fixing state.
6. Continued division of plant and bacteria cell and
formation of mature root nodule.
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Steps in Formation of Root Nodule
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Steps in Formation of Root Nodule
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Nitrogen Fixation
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Bioremediation
• Microorganisms are the Earth’s greatest
chemists.
• They can be used to:
▲Extract valuable metals from low grade ore
(microbial leaching).
▲Clean up the environment (bioremediation).
• Bioremediation is the use of microorganisms to
clean up pollution created by human activity e.g.
petroleum and pesticides.
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Bioremediation of Petroleum
• Petroleum is a rich hydrocarbon (HC) source and many
organisms including bacteria, mold yeast, cyanobacteria
and blue green algae is capable of aerobically oxidize it.
• This type of microbial activity is important in the
cleanup of oil and other pollutants.
• In a large oil spill the volatile HC fractions will evaporate.
• Hydrocarbon oxidizing microorganisms develop quickly
on the oil film and attach to the aliphatic and aromatic
components.
• The will oxidize these HC in the oil to CO2.
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Hydrocarbon Oxidizing bacteria
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Bioremediation of Xenobiotics
• It has been shown that HC oxidizing bacteria can
increase in # to 103-106 shortly after an oil spill.
• Xenobiotics are chemically synthesized compounds
that are not naturally occurring.
• They include pesticides, polychlorinated biphenyls
(PCB, used in electric generation) dyes and many
chlorinated solvents.
• Many xenobiotics are structurally related to naturally
occurring compounds and as thus can be degraded by
microorganisms.
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Bioremediation of Pesticides
• Other Xenobiotics are different and therefore
degradation in nature is very slow.
• The most common xenobiotics are pesticides.
• Over 1000 pesticides are market for chemical pest
control e.g. herbicide, insecticide and fungicide.
• Pesticides include variety of chemicals types including
chlorinated compounds, aromatic rings and nitrogen
and phosphorus containing compounds.
• Some of these compounds are suitable carbon source
and electron donors for some microorganisms.
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Bioremediation of Pesticides
• If the pesticide can be degraded by
microorganisms then it will prevent toxic
build up in the soil and water table.
• Chlorinated pesticides are recalcitrant
and can persist for more than 10 years
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Persistence of Herbicides and Insecticides
in Soil
Substance
Chlorinated insecticide
DDT
Chlordane
Organophosphate insecticide
Malathion
Parathion
Herbicides
2,4-D
2, 4,5-T
Atrazine
Time for 75-100% disappearance
4 years
5 years
12 weeks
1 week
4 weeks
20 weeks
40 weeks
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Bioremediation and Plastics
• Another major environmental concern is the disposal
of solid waste particularly plastic.
• The plastic industry produce 40 billion kg of plastic
each year, 40% of which end up in landfills.
• Plastics are xenobiotics polymers of various types
including:
╬Polyethylene
╬Polypropylene
╬Polystyrene
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Bioremediation and Plastics
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Bioremediation and Plastics
• Many of these polymers are recalcitrant and
remain in the landfill for decades.
• One solution is the use of biodegradable
polymers such as photobiodegradable
plastics, starch-linked and microbially
synthesized plastics.
• Photobiodegradable plastics are attacked by
UV light (from sunlight) generating polymers
which are amenable to microbial attack.
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Biodegradable Plastics
• Starch-based plastics incorporate starch as a for
a biodegradable polymer.
• Starch digesting bacteria in the soil attack the
starch releasing polymer fragments which are
degraded by other microorganisms.
• Microbially synthesized plastic e.g. poly-βhydroxyalkonate (PHA) is synthesized by
microbial cells and can be degraded by
microorganisms.
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