Horizontal gene transfer is widespread

July 2014

Photo from Creative Commons
From GM day-1, there's been a culture of denial over the possibility of artificial genes moving between organisms (horizontal gene transfer).
 
Some lip-service has been paid to the danger of anti-biotic-resistance marker genes (ARMs)* moving from GM crops to bacteria in the environment to create untreatable diseases. Europe even decided to ban GM crops containing such genes, but somehow it never seems to have happened.
A recent publication whose lead author advises GenĂ˜k (Norwegian Centre for Biosafety) and who serves on the European Food Safety Authority GMO panel admits the existence of problems. His paper is entitled “Detecting rare gene transfer events in bacterial populations”, and it reasons that horizontal gene transfer could never become significant in a natural, complex environment.
 
A key concern noted is that large-scale growing of GM crops results in “multitudinous opportunities for bacterial exposure” to the artificial DNA and, therefore, opportunities for horizontal gene transfer. However, assuming that the bacteria exposed exist in a highly complex environment which naturally limits their growth, mathematical modelling shows the problem would never be big enough to be a problem.  
 
It's also noted that the scientific search for evidence of horizontal gene transfer “suffers from significant methodological limitations, model uncertainty and knowledge gaps”. The main methodological limitation is that DNA in microbes can only be analysed after they have been cultured in isolation to increase the amount of the unknown DNA. Most microbes can't be grown in the laboratory. It seems that due to the presumed rarity of gene transfer, this technical problem is assumed to be unimportant.
 
Another take on this is that, if you put enough of them out there, the 'rare' gene transfers will become quite a lot of gene transfers. And the 'rare' gene transfers might not actually be so rare at all, but simply undetected due to the 'methodological limitations'.
 
Over a year before this report came out, the assumption of gene-transfer rarity had already been blown out of the water by a study which found a neat way round the technical difficulty of detection.
 
While America with its huge tracts of GM monocultures turns a blind eye to the possibility of wayward genes, Chinese scientists had a look in the six main rivers of their land. They found synthetic ARM genes in every one [1].
 
Ironically, the Chinese scientists overcame the difficulty in detecting horizontally transferred DNA in nature by using horizontal transfer of that same DNA in their laboratory. Unable to culture the bacteria from the rivers to the point where there was enough DNA to analyse, the scientists extracted the DNA from the river samples and transferred it into a bacterium they could culture in the lab. What they found was artificial ARMs.
 
Another assumption which has hampered the investigation of horizontal gene transfer has been that any DNA transfer would have to involve a whole gene before it would be functional in any way.
 
GM regulations and detection have, therefore, focused on identifying stretches of artificial DNA known to code for a protein.
 
This has hugely reduced the perceived potential for artificial DNA to move into bacteria and cause a problem. Science now shows that short and damaged stretches of DNA (ubiquitous in the environment) are readily taken up and incorporated into microbes, while the overlap between regulatory and protein-coding DNA could make these functional, or disruptive, in many ways.
 
Indeed, the shorter the fragment of DNA the more likely it is to find a suitable section of a foreign genome to insert into.
 
Concerns about the horizontal transfer of small viral (and other) DNA 'promoters' which force DNA expression have been repeatedly brought to regulators' attention by the Institute of Science in Society.
 
So-called 'decontamination' of hospital waste (which may harbour anti-biotic resistant bacteria) and of industrial waste from factory-scale use of GM microbes focus on killing the organisms. All the artificial DNA with its ARMs and viral promoters is being churned out into the environment, largely intact.
 
The World Health Organisation has released its 2014 report on antibiotic resistance in which it sounds the alarm that the last resort drug has been breached. It rightly exhorts the world's nations to avoid overuse and abuse of antibiotics. However, the report omits the role of GM technology, which the Chinese river study demonstrates is a major and continuing source of the current problem.
 
UK Prime Minister, David Cameron, has got in on the act and announced that Britain will take the lead in finding out why no new antibiotics are rolling off the lab benches, and in encouraging their development. A review of the situation will be headed by an economist, while the English Chief Medical Officer tells us that “New antibiotics made by the biotech and pharmaceutical industry will be central to resolving this crisis which will impact on all areas of modern medicine”. 
 

OUR COMMENT

 
Rather than throwing money at new antibiotics, perhaps we'd do better to put our attention on preserving the value of the ones we already have by restricting their use to the treatment of disease (instead of condoning all the antibiotics and ARMs now being churned into our environment by industry).
 
Westminster isn't mentioning the role of GM feed-crops in escalating antibiotic resistance, nor the fact that it is the uncontrolled production and dissemination of ARMs in biotech crops made by the biotech industry and uncontrolled production and use of antibiotics by the pharmaceutical industry which have led to the crisis in the first place.
 
The potential for novel pathogens to arise after making use of the novel DNA around them and further altering it to suit their purpose is huge, and already in progress in China at least.
 
Suggest to the Prime Minister that, rather than throwing money at industry to invent new antibiotics, he should start by removing all spurious antibiotics and ARMs from our food chain. Then, he should throw some money at reducing the need for medications by improving the diet of the people and the availability of fresh, local produce.
 
[1] A RECIPE FOR MRSA - March 2013

*ARMs are included in some artificial DNA constructs to help genetic engineers pick out successfully transformed organisms. They have no function in the final product, and can be eliminated from the final organism if the will is there.
 
SOURCE 
  • Dr. Mae Wan Ho, Horizontal transfer of GM DNA Widespread, Institute of Science in Society Report, 9.06.14
  • Antibiotic resistance: Cameron warns of medical 'dark ages', BBC 3.07.14

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