Food safety issue--Antibiotic-resistant marker genes

During the process of genetic modification, marker genes are used to check whether particular cells have taken up the modified gene. Antibiotic-resistant marker genes are one type of marker gene. If a cell is resistant to the particular antibiotic, this shows that the cell has taken up the modified gene. Some people have suggested that antibiotic-resistant marker genes could be transferred into the bacteria in our gut, along with the resistance to the particular antibiotic. If this happened, the particular antibiotic, if prescribed to treat an infection, would not work in that person.
The Advisory Committee on Novel Foods and Processes (ACNFP) is an independent scientific committee that advises the Food Standards Agency. In 1996, when the first GM maize was approved as a food, the ACNFP raised the concern that antibiotic resistance marker genes might be transferred from GM plants to the bacteria in our digestive systems. At that time, the ACNFP concluded that there was a low risk of this happening. Since then, further research has shown that the risk of transfer is even lower than originally thought.
However, to remove this risk completely, the ACNFP has recommended that these marker genes should be removed once the original genetic modification has been carried out. There is general agreement among regulators and companies developing genetic modification technology that using antibiotic resistance markers should be phased out.
The European Directive on this issue states that, by 31 December 2004, antibiotic resistant marker genes that may have ‘an adverse effect on human health and the environment’ should be phased out from GM organisms that could enter the food chain. (European Directives are binding on Member States but national governments decide how they will implement them.) Antibiotic resistant marker genes authorised for research purposes only, and not for the food chain, should be phased out by the end of 2008. This would leave currently approved crops containing antibiotic resistant marker genes on sale. However, this generation of crops is likely to be superseded by newer varieties that do not contain these genes.

I loved you at Thursday, June 14, 2007

What happens when people eat GM food?

Human beings have always eaten plants and animals, which means we have always eaten their DNA without it causing any health problems. Given that GM DNA is still DNA, eating it should not pose any greater risk than eating unmodified DNA. Indeed, no one has ever been reported as suffering from illness because the food they had eaten had been genetically modified.
When someone eats GM food it is processed in the same way as non-GM food. When we eat any food, our digestive systems break down the tissue, the proteins, and the DNA in the food. The DNA in GM food has the same structure as non-GM DNA and is broken down in the same way. Most DNA that is consumed, whether GM or not, is broken down in our stomachs and intestines.
Sometimes, the DNA from the food we eat isn't broken down. However, it is unlikely that this DNA will become part of our genetic material by passing into our cells – any non-human DNA should simply be broken down in the cell.

I loved you at Thursday, June 14, 2007

Different types of GM food

*Herbicide- and insecticide-resistant soybeans, corn, cotton ,flaxseed and canola
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*Sweet potato resistant to a virus that could decimate most of the African harvest
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*Bovine somatotropinprotein (BST) supplement to increase cows' milk yields
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*Rice with increased iron and vitamins that may alleviate chronic malnutrition in Asian

*Variety of plants able to survive weather extremes
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*Bananas that produce human vaccines against infectious diseases such as hepatitis B
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*Plants that produce new plastics with unique properties
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*Fish that mature more quickly
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*Fruit and nut trees that yield years earlier
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*Golden rice: a rice that can make beta-carotene (which our bodies make into vitamin A) is grown in parts of the world where people are deficient in vitamin A
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*Potatoes that contain extra protein go on sale

*Salt tolerant tomatoes

*Sunflowers resistant to white mould marketed
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*Decaffeinated coffee
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*Longer lasting tomatoes that can be grown on land that can't normally be used for agriculture because of salt level in soil

*Cheese produced with the help of chymosin from GM micro-organisms

I loved you at Friday, June 08, 2007

Principle of GM food

*Inserting genes
When a plant, for example, is modified by inserting a gene from another plant into it, this is the process:

1. A plant that has the desired characteristic is identified.

2. The specific gene that produces this characteristic is located and cut out of the plant’s DNA.

3. To get the gene into the cells of the plant being modified, the gene needs to be attached to a carrier. A piece of bacterial DNA called a plasmid is joined to the gene to act as the carrier.

4. A type of switch, called a ‘promoter’, is also included with the combined gene and carrier. This helps make sure the gene works properly when it is put into the plant being modified. Only a small number of cells in the plant being modified will actually take up the new gene. To find out which ones have done so, the carrier package often also includes a marker gene to identify them.

5. The gene package is then inserted back into the bacterium, which is allowed to reproduce to create many copies of the gene package.

6. The gene packages are then transferred into the plant being modified. This is usually done in one of two ways:
- by attaching the gene packages to tiny particles of gold or tungsten and firing them at high speed into the plant tissue. Gold or tungsten are used because they are chemically inert – in other words, they won't react with their surroundings
- by using a soil bacterium, called Agrobacterium tumefaciens, to take it in when it infects the plant tissue. The gene packages are put into A. tumefaciens, which is modified to make sure it doesn't become active when it is taken into the new plant.

7. The plant tissue that has taken up the genes is then grown into full size GM plants.

8. The GM plants are checked extensively to make sure that the new genes are in them and working as they should. This is done by growing the whole plants, allowing them to turn to seed, planting the seeds and growing the plant again, while monitoring the gene that has been inserted. This is repeated several times.
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*Altering genes
Genetic modification does not always involve moving a gene from one organism to another. Sometimes it means changing how a gene works by 'switching it off' to stop something happening. For example, the gene for softening a fruit could be switched off so that although the fruit ripens in the normal way, it will not soften as quickly. This can be useful because it means that damage is minimised during packing and transportation. Controlling this gene 'switch' may also allow researchers to switch on modified genes in particular parts of a plant, such as the leaves or roots. For example, the genes that give a plant resistance to a pest might only be switched on in the bit of the plant that comes under attack, and not in the part used for food.

I loved you at Friday, June 08, 2007

Introduction to GM food

Genetically Modified (GM) foods are produced from genetically modified organisms (GMO) which have had their genome altered through genetic engineering techniques. The general principle of producing a GMO is to insert DNA that has been taken from another organism and modified in the laboratory into an organism's genome to produce both new and useful traits or phenotypes. Typically this is done using DNA from certain types of bacteria. GM Foods have been available since the 1990s, with the principal ones being derived from plants; soybean, corn, canola and cotton seed oil.[1] Although "biotechnology" and "genetic modification" commonly are used interchangeably, GM is a special set of technologies that alter the genetic makeup of such living organisms as animals, plants, or bacteria. Biotechnology, a more general term, refers to using living organisms or their components, such as enzymes, to make products that include wine, cheese, beer, and yogurt. Genetic modification is done either by altering DNA or by introducing genetic material from one organism into another organism, which can be either a different variety of the same or a different species. Combining genes from different organisms is known as recombinant DNA technology, and the resulting organism is said to be "genetically modified," "genetically engineered," or "transgenic." GM products (current or in the pipeline) include medicines and vaccines, foods and food ingredients, feeds, and fibers.

I loved you at Friday, June 08, 2007

Dairy product Processing and impact on microbiological safety

Milk and cream
Pasteurisation is sufficient to destroy pathogenic milk-borne vegetative bacteria. Illness resulting from consumption of pasteurised milk is rare. However, where outbreaks have occurred, these were attributed to inadequate pasteurisation, post-pasteurisation contamination and/or temperature abuse.

Cheese
A number of processing factors influence the growth and survival of pathogens in cheese,
including the severity and duration of heat treatment (including curd cooking); pH; salt
concentration; water activity; and maturation/ripening. These outbreaks have resulted from faulty controls in cheese production; use of contaminated starter cultures or contaminated ingredients; post-pasteurisation contamination; or mishandling during transport and/or distribution.

Dried milk powders
Micro-organisms in dried milk powders will not grow due to low water activity, however, they may survive for long periods and resume growth when the powder is reconstituted and stored under favourable conditions. Heat-treatments given prior to spray-drying are severe enough to destroy all vegetative pathogens in raw material. However, there is opportunity for environmental contamination during spray-drying and subsequent storage.The outbreaks were caused poor plant hygiene; contamination and abuse of reconstituted products; and outgrowth of bacterial spores.

Concentrated milk products
Microbial pathogens are generally not associated with concentrated milks due to the low water
activity of these products. Pasteurisation of cream used in butter manufacture results in the destruction of vegetative microorganisms, although preformed toxins and spores may carry over to butter. The preservative properties of butter are based on moisture distribution. In addition salt in moisture droplets also have a preservative effect.

Ice-cream
The heat treatment applied to ice cream mix destroys pathogenic micro-organisms. However,
pathogens may be introduced with the addition of ingredients. Pathogens will not grow in icecream, but may survive freezing. The outbreaks have been linked to the use of raw ingredients or improper heat treatment during preparation of ice-cream in the home, and contamination during commercial icecream manufacture.

Cultured and fermented milk products
The heat treatment of milk is sufficient to destroy vegetative micro-organisms and rapid growth of starter cultures inhibits the outgrowth of spore-formers. Pathogenic micro-organisms are
prevented from growth by the low pH; the presence of lactic acid, and by refrigerated storage.

Dairy desserts
Heat treatment by pasteurisation or UHT results in the destruction of vegetative cells.
Contamination may occur after heat treatment with the addition of further ingredients, or through survival of spores of B. cereus.

Dairy-based dips
Where pasteurisation or other heat treatments are employed, vegetative cells will be destroyed.
However, spore-formers can survive heat treatments and other hazards can be introduced with
the addition of heat labile ingredients after heating. The low pH of these products assists in their
microbial stability.

I loved you at Monday, April 30, 2007

Ability of bacterial pathogens to survive pasteurisation?

Heat resistance studies conducted using either pilot plant- and/or or commercial-scale HTST
pasteurisation equipment, together with additional data from studies using various laboratory techniques, have confirmed that the vegetative forms of 11 of 18 pathogenic species
considered in this review are destroyed by both batch (63ºC for 30 minutes) and HTST (72ºC
for 15 seconds) pasteurisation, with a reasonable margin of safety. These species are:

• Brucella abortus
• Mycobacterium tuberculosis
• Campylobacter jejuni
• Mycobacterium bovis
• Campylobacter coli
• Salmonella enterica serotypes
• Coxiella burnetii
• Streptococcus pyogenes
• Pathogenic Escherichia coli (0157:H7)
• Yersinia enterocolitica
• Listeria monocytogenes

I loved you at Tuesday, April 24, 2007