Transcript EBT Presentation

The use of genetic engineered organisms
for pollution abatement
An abatement to air, water and soil pollution
GM Food – food that have had their genes
modified to be resistant against insects that
may do harm to them, thus reducing the
amount of insecticides and pesticides used.
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Pharmaceutical benefits, vitamin-enhanced
grains, and those with amino acids and other
nutritional features.
Increases drought and extreme-temperature
tolerance
Resistance to a variety of pests and diseases
Increase the amount of food for the world so as
to ensure that sufficient food is available.
Reduce the number of herbicides used to control
weeds, facilitating minimum tillage or no-tillage
farming, reducing soil erosion and surface water
contamination.
Environmental implication: “Bt” corn is resistant
to corn borers attack, but there are concerns
that a Bt-resistant borer may develop.
 ‘Super weeds’ might develop a resistant against
herbicides.
 GMO crops may also cross breed with some
other closely related species, leading to
transgenic pollution.
 Loss of genetic resources due to accidental cross
breeding.
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GM Food in the United States
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As of 2000, 68% of such crops come from the
U.S.
Soybeans and corn in U.S. make out 82% of all
GM crops harvested in 2000, in which 74% were
modified for herbicide tolerance, 19% with
insect pest resistance, and 7% with both
herbicide tolerance and pest tolerance.
Acreage of GM crops has increased from
approximately 4.3 million acres in 1996 to 109
million acres
Pesticide and herbicide decreased, resulting in
increase of yields.
“Transgenic” pollution – Crops pollinated with
biotech genes can lose their organic status if
they have been cross polluted.
 Dangerous on countries that rely highly on
agriculture (with most countries pledging
against GM food).
 Health effects of consumption and at what dose
is unknown.
 Create a class of insects resistant to it.
 Low reduction in terms of use of pesticides –
only by 2.5%.
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Phytoremediation, able to clean up transgenic
pollutants.
 Few methods to phytoremediation:
- Phytovolatilization
Plants take up contaminants
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from soil and release them as volatile form into the
atmosphere through transpiration
- Phytodegradation
Complex organic pollutants are
degraded into simpler molecular and incorporated into plant
tissues to aid plant growth.
- Phytoextraction
Use of plant to take up metal
contaminants from soil through the absorption by plant
roots.
Contaminants
move to the
leaves and
volatilize into the
atmosphere.
It is changed and
modified along the
way.
Water travels from the
roots to the leaves along
the vascular system of the
plant.
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No plants even to this date; are found with natural ability to
 accumulate
 or degrade mercury.
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Transgenic plants are developed to remove mercury
How?
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(Mer B) and (Mer A) are enzymes in bacteria
 Responsible for the process,
 Converts organic mercury to elemental mercury that is less toxic.
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Mer B converts
 organic mercury (CH3Hg) to ionic mercury Hg (II),
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Mer A then reduced
 ionic mercury Hg (II) to the volatile elemental mercury Hg (0)
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Genes were introduced in
 Arabidopsis thaliana plant.
 Yellow Poplar plant
 Eastern cottonwood, Populus deltoids
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Result :
 Able to grow on up to 10μM methyl mercury concentrations,
 40-times higher than the maximum concentration tolerated by WT seedlings
 10-times higher concentrations than plants that express MerB alone
 Combining gene resulted in more efficient detoxification of organomercurial
compounds than did merB alone
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Results:
 Transfer of Mer A producing gene to Yellow Poplar plant
 Ability to volatilize 10 times more mercury than control plants.
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Eastern cottonwood, Populus deltoids
 Another candidate plant used for Phytoremediation.
 Modified with Mer A gene.
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Transgenic shoots
 Grew normally on a medium with 25μM Hg(II)
 A concentration which killed wild-type shoots.
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In addition, the transgenic plant
 Produced up to 4 times more elemental mercury Hg (0) than wild-type
plants.
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Evidently shows that the plants are capable of transforming
mercury to its less toxic form more efficiently.
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Another experiment is carried out in polluted soil
 With mercuric ion at a toxic concentration of 400 ppm Hg (II).
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By 2 weeks,
 All non-transgenic plant had died
 While the transgenic cottonwoods were still alive.
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Enzymes in plant roots break down (degrade) organic
contaminants. The fragments are incorporated into new
plant material.
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Trinitrotoluene (TNT)
 One of the most persistent and dangerous explosives.
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The use and disposal of TNT has
 Resulted in the contamination of many sites.
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While many plant species that are able to
break down TNT in their own tissue, not
many can last long in TNT contaminated site.
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Affects their growth and development.
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Entereo cloaca, a soil bacterium
 was able to utilize ester explosive as its source of nitrogen.
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Enzymes produced by this bacterium are
 PETN reductase and Nitro-reductase.
 Both enzymes degrade TNT into less harmful product.
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The genes expressing the production of these 2 enzymes are
introduced into the plant,
 Tobacco (Nicotiana tabacum)
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When exposed to 0.25 mM TNT
 Wild type plant became chlorotic and lose mass
 Transgenic plant continue to grow
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The transgenic plant are
 more resistant to TNT.
 metabolized TNT at far greater rate than the control plants.
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Plants absorb contaminants through system of roots
 Store them in roots
 Or transport them up into the stems and leaves
 It will carry on absorbing contaminants until it is being harvested
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After the plants are allowed to absorb the contaminants for some
time, they are harvested to either be
 Disposed by incineration
 Or be composted to recycle metals.
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After the harvest,
 Soil contain a lower concentration of contaminant.
 This growth and harvest cycle is repeated for a number of times to achieve a
considerable clean up.
 After the process, remediated soil can be put into other beneficial uses.
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A problem in the use of hyperaccumulator
 Do not have enough biomass
 & growth rate to be applied in large scale practices.
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To resolve this, Phytoextraction can be further improve by
 Transferring genetic traits from hyper-accumulator into plants that has
high biomass and growth rate.
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In this way,
 plants with high biomass and growth rate
 will also have the ability to take up high quantity of metals.
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E.g. Poplar and willow
 do not accumulate metals to high concentration.
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However, they are still effective remediators
 because of their deep root system
 and biomass.
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Hence, they are excellent candidate to be genetically
engineered to have traits of hyper-accumulators.
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While genetically modified food is known as a
way to reduce the amount of pesticides and
herbicides that are used in order to abate
pollutions like air and water, there is always a
slight chance that their might be transgenic
plants that may be spun out of this
genetically engineering crops.
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Phytoremediation, on the other hand, uses
transgenic plants to control land pollution,
should there be more than the required
amount of heavy metals present in the soil
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