Aug 07 2014

Antibiotic Resistant Markers in GM Crops

Neil deGrasse Tyson stepping into the public GMO debate has raised the profile of this issue, and so I am likely going to return to the issue as new claims surface.

Recently Jeffrey Smith posted a Youtube video in which he directly challenges Tyson on his claim that people should “chill out” about transgenic GM technology.  Smith is an anti-GMO activist, founder of the Institute for Responsible Technology, and producer of the anti-GMO documentary, Genetic Roulette — The Gamble of Our Lives. 

For further background, Smith attended Maharishi University of Management in the 1980s and was a Natural Law Party member in 1996 and participated in a TM-Sidhi program yogic flying demonstration in Des Moines, Iowa.

His latest anti-GMO effort is full of specific claims I have not previously addressed. He makes an attempt to seem as if his claims are scientific, but upon investigation it quickly becomes clear he is cherry picking studies and then wildly speculating way beyond the evidence. It would take many articles to deconstruct his 20 minute Gish-galloping video, so I will pick out a few prominent claims.

Antibiotic Resistant Markers

One main focus of Smith’s video is that genes inserted into GMO crops can find their way through horizontal transfer into the bacteria in our GI system. There the genes can cause toxicity and bestow antibiotic resistance onto the bacteria.  Here Smith is employing a tactic common among vaccine-deniers – he partially understands the science, just enough to overhype a risk that has already been carefully evaluated.

Use of genes that confer antibiotic resistance are sometimes used in the GM process. These are used as markers, so that the scientists can find the plant cells that have the new genes. They simply treat the culture with a specific antibiotic, and those that have the resistance gene inserted will survive.

It is also true that horizontal transfer – genes going from one organism to another – is theoretically possible. However, there is a big difference between theoretically possible and probable.

The FDA, in fact, has conducted a thorough analysis of the likelihood of such transfer. They found:

It is highly unlikely that antibiotic resistance genes could be transferred from plant genomes to gut microorganisms. First, there are no known mechanisms for the direct transfer of plant genomic DNA to microorganisms. Second, there are several barriers to potential transfer. These include degradation by acid and nucleases in the stomach and intestines, the bacterial restriction and modification systems that destroy foreign DNA that enters the cell, the absence of homologous ends for efficient integration into the bacterial genome, and lack of selective pressure.

Further, the antibiotic resistance genes would be competing with the entire genome of the plant. Also, often eukaryotic promoters are used, which would not work in the bacterium. However, at some stages in the GM process viral or bacterial promoters are used, and these could function in the bacterium. Taking into consideration all factors, the probability of a marker gene for antibiotic resistance ending up in a gut bacteria and proliferating is negligible.

Despite this, and in order to err on the side of caution, the FDA has approved antibiotic resistant genes only for antibiotics that are not critical to medicine, that are not typically used orally, and that confer resistance that is already common among bacteria. Therefore in the highly unlikely event that antibiotic resistance transferred from plant to bacteria, it would not contribute to overall antibiotic resistance.

It can further be noted that we consume bacteria all the time that have genes for antibiotic resistance, and these are far more likely to transfer to other bacteria. So again: any plant-to-bacteria horizontal transfer would be negligible compared to the background of bacteria-to-bacteria transfer already present.

Academicsreview also evaluated this claim, reviewing the peer-reviewed literature, and came to the same conclusions.

Smith did not mention any of this information. He failed to put this risk into a reasonable scientific context, or to reflect the expressed opinions of the relevant scientific community or the regulations that are already in place. Instead he crafted a chain of increasingly unlikely speculation intended to stoke fears about non-existent risks.

In the video and in his prior documentary Smith makes many other claims in a similar manner – he talks about the risk of transfer of genes to humans, for example. He fails to point out that horizontal transfer occurs in nature (although a rare event, it happens over evolutionary time) and is not a particular risk from transgenic crops. Inserted DNA is typically outnumbered by a million fold by native DNA, and is competing with all the DNA from all other food that we eat.

It is also easy to fearmonger about “fish genes in our tomatoes,” for example. However, fish and tomatoes share about 60% of their genes, and people eat fish, which I understand contain 100% fish genes.

Other Fears

Smith also warns against new proteins from the gene insertion process. Again he begins with a scientific fact that is not disputed – the process of gene insertion can cause mutations in nearby genes. He extrapolates from this that new proteins in GMOs may be causing Alzheimer’s disease and other diseases. This is based on nothing except the exact same correlation fallacy used by the anti-vaccine movement: use of GMO is increasing, and these diseases are increasing, therefore…

There is no reason to suspect that transgenic proteins are any more risky to human health than any other proteins. Further, new proteins are extensively tested for their allergenicity and toxicity. The FDA lays out testing procedures to show that the proteins do not have allergenic properties – they are not resistant to digestion, and they do not have homology with known allergens, for example.

With regard to mutations in other proteins, the overall plants are tested to show that, other than the new desired gene, they are equivalent to the original parent plant. It should also be noted that in the process of making a GMO crop, the new plant with the inserted gene is back-bred to the desired cultivar multiple times in order to generate a new cultivar that is identical except for the addition of the new desired gene.

Of course this process is not perfect and risk free. No technology is risk free. Again, just as with the antivaxxers, zero risk is not a reasonable requirement and is designed to reject the technology.

In evaluating a new technology, the proper approach is to evaluate risk vs benefit, not to require zero risk. Smith and other anti-GMO activists do not fairly represent the scientific literature, but rather speculate wildly about potential risks without putting them into proper context. They further ignore or unfairly criticize the regulations and safety testing that are already in place.


Legitimate concerns that are raised are being addressed by the FDA and scientists – it’s right there in their publications. Reasonable, even cautious, measures are put in place, and testing is extensive.

It is also reasonable to monitor and review current regulatory and testing processes, even to criticize them, point out weakness, and recommend improvements. This should be a constant process of any complex technology where risks need to be managed. It’s always a work in progress.

It is easy, however, to take such working criticisms and misrepresent them as if they are fatal flaws, and the whole technology should be scrapped. Science also always deals with a certain amount of uncertainty, and that uncertainty can be used to stoke fears.

Such a hit job could be launched (and is) against any complex technology that involves risks and benefits, especially when human health is concerned. It can be done against vaccines, pharmaceuticals, the food industry, airline travel, the automotive industry – any technology.

Jeffrey Smith’s recent video, in my opinion, is an excellent example of a fearmongering propaganda hit job. Unfortunately, it is much easier to create fears than it is to calm them by deconstructing false claims.

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