The use of genetic engineered organismsfor 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.

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.

GM Food in the United States

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%.

Phytoremediation, able to clean up transgenic pollutants.

Few methods to phytoremediation: - Phytovolatilization Plants take up

contaminants 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.

Water travels from the roots to the leaves along the vascular system of the plant.

It is changed and modified along the way.

Contaminants move to the leaves and volatilize into the atmosphere.

No plants even to this date; are found with natural ability to accumulate or degrade mercury.

Transgenic plants are developed to remove mercury

How?

(Mer B) and (Mer A) are enzymes in bacteria Responsible for the process, Converts organic mercury to elemental mercury that is less

toxic.

Mer B converts organic mercury (CH3Hg) to ionic mercury Hg (II),

Mer A then reduced ionic mercury Hg (II) to the volatile elemental mercury Hg

(0)

Genes were introduced in Arabidopsis thaliana plant. Yellow Poplar plant Eastern cottonwood, Populus deltoids

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

Results: Transfer of Mer A producing gene to Yellow Poplar plant Ability to volatilize 10 times more mercury than control

plants.

Eastern cottonwood, Populus deltoids Another candidate plant used for Phytoremediation. Modified with Mer A gene.

Transgenic shoots Grew normally on a medium with 25μM Hg(II) A concentration which killed wild-type shoots.

In addition, the transgenic plant Produced up to 4 times more elemental mercury Hg (0)

than wild-type plants.

Evidently shows that the plants are capable of transforming mercury to its less toxic form more efficiently.

Another experiment is carried out in polluted soil With mercuric ion at a toxic concentration of 400 ppm Hg

(II).

By 2 weeks, All non-transgenic plant had died While the transgenic cottonwoods were still alive.

Enzymes in plant roots break down (degrade) organic contaminants. The fragments are incorporated into new plant material.

Trinitrotoluene (TNT) One of the most persistent and dangerous explosives.

The use and disposal of TNT has Resulted in the contamination of many sites.

While many plant species that are able to break down TNT in their own tissue, not many can last long in TNT contaminated site.

Affects their growth and development.

Entereo cloaca, a soil bacterium was able to utilize ester explosive as its source of nitrogen.

Enzymes produced by this bacterium are PETN reductase and Nitro-reductase. Both enzymes degrade TNT into less harmful product.

The genes expressing the production of these 2 enzymes are introduced into the plant, Tobacco (Nicotiana tabacum)

When exposed to 0.25 mM TNT Wild type plant became chlorotic and lose mass Transgenic plant continue to grow

The transgenic plant are more resistant to TNT. metabolized TNT at far greater rate than the control plants.

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

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.

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.

A problem in the use of hyperaccumulator Do not have enough biomass & growth rate to be applied in large scale practices.

To resolve this, Phytoextraction can be further improve by Transferring genetic traits from hyper-accumulator into

plants that has high biomass and growth rate.

In this way, plants with high biomass and growth rate will also have the ability to take up high quantity of

metals.

E.g. Poplar and willow do not accumulate metals to high concentration.

However, they are still effective remediators because of their deep root system and biomass.

Hence, they are excellent candidate to be genetically engineered to have traits of hyper-accumulators.

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.

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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