Environmental impacts of Genetically Modified Organisms (GMO’S)

Sivagurunathan .p

II M.Sc., Eco-Biotechnology

contact2sivas12@gmail.com

What is Gmo’s?

A genetically modified organism (GMO) or genetically engineered organism (GEO) is an organism whose genetic elements has been altered using genetic engineering techniques

These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one molecule to create a new set of genes.

  This DNA is then transferred into an organism, giving it modified or novel genes

History of GMO’S

The general principle of producing a GMO is to add new genetic material into an organism's genome. This is called genetic engineering and was made possible through the discovery of DNA and the creation of the first recombinant bacteria in 1973, i.e., E .coli expressing a Salmonella gene

Herbert Boyer then founded the first company to use recombinant DNA technology,

Genentech, and in 1978 the company announced creation of an E. coli strain producing the human protein insulin.

In 1986, field tests of bacteria genetically engineered to        protect plants from frost damage (ice-minus bacteria) at        a small biotechnology company called Advanced        Genetic Sciences of Oakland, California,         were repeatedly delayed by opponents of biotechnology. 

.    In the same year, a proposed field test of a microbe        genetically engineered for a pest resistance protein        by Monsanto Company was dropped

Transgenic Microbes

Bacteria were the first organisms to be modified in the laboratory, due to their simple genetics

       These organisms are now used for several purposes, and are           particularly important  in producing large amounts of            pure human proteins for use in medicine

   Genetically modified bacteria are used to produce the protein insulin to treat diabetes

Similar bacteria have been used to produce clotting factors to treat hemophilia and human growth hormone to treat various forms of dwarfism

The ice-minus bacteria constructed from P.syringae by removing genes that synthesize ice nucleating proteins. The ice minus strain was shown to inhibit frost damage to plants when the temperature drops a few degrees freezing.

For instance, the bacteria which cause tooth decay are called Streptococcus mutants.

These bacteria consume left over sugars in the mouth, producing lactic acid that corrodes tooth enamel and ultimately causes cavities.

Scientists have recently modified Streptococcus mutants to produce no lactic acid.

These transgenic bacteria, if properly colonized in person's mouth, could reduce the formation of cavities.

The Transgenic microbes are involved in Bioremediation of Metals,Wastes,Hydrocarbons,etc..,

Example

Pseudomonas putida strains discovered by Dr. A.M chakrabarthy are involved in the degradation of hydrocarbons like Naphthalene, Camphor, Octane, Xylene,etc..,

Plasmids are common vector for cloning and moving transgenes from one organism to other,in conjugation process these trans genes move into the other bacteria in the Environment

Some conjugative plasmids are highly promiscuous in their ability to transfer widespread dispersion of antibiotic resistant genes to the normal microbes.

Genetically engineered viruses could infect any harm non target hosts. Because viruses are obligate intracellular parasites ,they require metabolizing

(living)cells to replicate their genomes and make their progeny.

The Genetically modified organisms are also used as a weapon for the biological warfare.

Transgenic Animals

      Transgenic animals are used as experimental models       to  perform phenotypic tests with genes whose        function is unknown

Genetic modification can also produce animals that are susceptible to certain compounds or stresses for testing in biological research

Other applications include the production of human hormones such as insulin.

Transgenic animals are produced for specific economic traits.

For example, transgenic cattle were created to produce milk containing particular human proteins, which may help in the treatment of human emphysema

Transgenic animals are produced as disease models (animals genetically manipulated to exhibit disease symptoms, so that effective treatment can be studied

Agricultural Applications

Farmers have always used selective breeding to produce animals that exhibit desired traits (e.g., increased milk production, high growth rate)

Transgenic cows exist that produce more milk or milk with less lactose or cholesterol.

pigs and cattle that have more meat on them, and sheep that grow more wool.

Scientists are attempting to produce disease resistant animals, such as influenza-resistant pigs

Medical Applications

The transgenic animals are involved in the xenotransplantation 

The transgenic animals are also involved in the Human gene theraphy

Production of Growth hormones

Toxicity-sensitive transgenic animals have been produced for chemical safety testing.

Human health risks:

Such as Allergies, and unknown effects on human health from foreign genes

Economic concerns:

Bringing a genetically modified organisms to market is a lengthy and costly process. Exclusive rights and enforcement may also be difficult

The primary environmental concerns about releases of transgenic fish, for example, include competition with wild populations, movement of the transgene into the wild gene pool, and ecological disruptions due to changes in prey and other nutrients requirements in the transgenic variety versus the wild populations

The transgenic animals does not have a longer Shelf life Example:Dolly (sheep) born on 5 july 1996 and died at feb 14 2003.

Transgenic Plants

     Transgenic plants have been engineered to possess      several desirable traits, including resistance to     pests, herbicides or harsh environmental conditions,     improved product shelflife, and increased nutritional value.

Since the first commercial cultivation of genetically modified plants in 1996, they have been modified to be tolerant to the herbicides glufosinate and glyphosate, to be resistant to virus damage as in Ringspot virus resistant GM papaya, grown in Hawaii, and to produce the Bt toxin, a potent insecticide.

Increasing the Crop Yield

Disease Resistance To Plants

Bioremediation of contaminated soils

Insect Resistance To Plants

Salt tolerance to Plants

     Genetic engineering is commonly offered as a hope to improve crop production efficiency by enhancing crop tolerance to various abiotic stresses such as drought, salt and water (Wang et al. 2003, Yamaguchi &Blumwald 2005)

Herbicide-tolerant crops permit the use of broad spectrum herbicides such as glyphosate glufosinate at the post- emergence phase.Growers of GMHT crops versus traditional crops benefit mainly from lower costs due to simpler weed control.

Insect-resistant GM crops are revealing benefits for farmers,most of all where yields are hampered by high pest or weed incidence or where the development of resistant pests impedes the use of pesticides (FAO 2004, Raney 2006)

The benefits related to the adoption of Bt-crops may comprise both higher yields and significant reductions in pesticide use for crops

The use of Bt-crop can lower costs by reducing the application of insecticides for pest control

Gene flow to wild Relatives:

Pollen transfer to Wild relatives and hybrid formation

Survival and Reproduction of Hybrids

Survival &reproduction outside of cultivated areas

Transgenic population (hybrids / crops) with enhanced fitness compared to wild population

Environmental Fate of Transgenic products

Persistence, degradation and spread of transgenic products

Accumulation of Transgenic products in soil.

Emission of transgenic products into water

Effects on Non-Target organisms:

For the currently commercially cultivated GM crops, it is generally accepted that toxic effects on non- target organisms are restricted to GM crops expressing insecticidal proteins(Wolfenbarger & Phifer 2000, Dale et al. 2002, Conner et al. 2003).

There are concerns that insect-resistant GM crops could harm resistance conferred via expression of Cry-proteins organisms other than the pest(s) targeted by the toxin. Insect from Bacillus thuringiensis (Bt) is by far the most common trait that has been engineered into plants. To date Bt-toxins1) represent the only insecticidal proteins expressed in commercial GM crops (James 2005, AGBIOS 2006).

Several authors have proposed procedures on how to assess the risks that insect resistant GM crops may pose to non-target organisms (Cowgill & Atkinson 2003, Duttonet al. 2003, EFSA 2004, Poppy & Sutherland 2004, Rose 2006).

Effects of Bt-crops expressing Cry1-proteins on non-target arthropods(moths and butterflies) Lepidoptera (Dutton et al. 2003).

Typically, they were selected according to their importance in providing relevant ecological functions in crops, such as natural regulation of pests, as well as bees and other pollinating insects that are often essential for high yields in crop production

Effects on beneficial insects (predators and parasitoids)

A lot of attention has been paid in recent years to investigate potential adverse effects of Bt-crops expressing Cry1-proteins on beneficial insects such as predators and parasitoids ( O’Callaghan et al. 2005, Romeis et al. 2006)

Predators and parasitoids (so-called natural enemies) are important regulators of insect pest populations, playing a vital role in biological control.

Effects on pollinators

Many insect species are known to act as pollinators of various crops and wild plants. They are therefore of great ecological and economic importance. Among the various insect pollinators, honey bees are the best known, but it is now recognized that other species like bumble bees and solitary bees are also important in ensuring pollination of many plant species.

Pollen feeding represents the most likely route of exposure to Bt-toxins for adult honey bees (Malone & Pham-Delegue 2001), because pollen is the main source of proteins for adult bees (Crailsheim 1990

Impacts of GM crops on soil ecosystems

Bacillus thuringiensis (Bt) is a soil bacterium, Bt- toxins are naturally occurring in soils. In addition, Bt-spray formulations are commonly used for insect control in agriculture and forestry (Walker et al. 2003)

Due to their high specificity they are regarded as environmentally friendly and have rarely been found to have adverse effects on non target organisms and human health (Glare & O’Callaghan 2000

Bt-toxins expressed in Bt-crops can enter the soil system via root exudates, senescent plant material remaining on or in the ground after harvest, as well as damaged and castoff dead root cells (Saxena et al; 1999, Zwahlen et al. 2003a, Baumgarte & Tebbe 2005).

Persistence of Bt-toxins in soil is primarily depending on the protein quantity added and on the rate of inactivation and degradation by biotic and abiotic factors (Dubelman et al. 2005).

Resistance Development:

Resistance development in target pest / disease

Loss of Effectiveness of transgenic product

Selection of herbicide tolerant wild plants/Reduced effectiveness of specific herbicide

Changes in Pest/disease control strategies

Effects on Agricultural methods & cropping system:

Changes in cultivation practice/tillage

Changes in cropping intervals/cultivation area

Changes in spectrum of pests, diseases and beneficial organisms

Changes in physical, chemical and biological soil characteristics

Decrease in soil quality/Effects on biodiversity