[persiphone]

Originally Posted by dreadgeek

Can you explain what you mean by "DNA specifically engineered to be antibiotic resistant" and "pumped into the food supply"? I ask for a couple of reasons:

1) Antibiotics do not, strictly speaking, affect 'naked' DNA. (Here I mean DNA that isn't in some living thing.) Antibiotics affect, well, bacterials but not viruses (RNA) and DNA is RNA with an extra strand, some sugar and one different base (T in DNA is U in RNA). So what doesn't effect RNA also doesn't effect DNA.

2) What do you mean by "pumped into the food supply" in the context of DNA? This seems to violate the central dogma of molecular biology. Put simply, DNA codes for proteins. So DNA that isn't coding for something in the context of being in the presence of a living thing isn't' doing anything. So how can DNA, absent a body in which to express itself, be *doing* anything? Are you saying that it is making antibiotic resistant proteins? That doesn't really make sense unless you are talking about it being inside a living thing.

3) Are you saying that someone cooked up DNA as a bacteriophage (a virus that infects bacteria)? If so, why on Earth would they have it code for resistance to antibiotics since the whole purpose of a bacteriophage would be to try to kill a bacteria not make it more resistant to antibiotics. What's more, there's a far less expensive way they could get the same effect. Simply have people take too many antibiotics, not use them correctly, use a lot of antibacterial soaps so that we're constantly turning the selective volume on bacteria up to eleven. Wait, that's what we're doing now.

I will admit that I do not read all of the literature but I do try to keep up with what is happening in molecular genetics particularly as it relates to our ongoing battle against pathogens. I'm not aware of the work you're talking about and really am not sure that I understand what you're saying. I don't want to derail the thread so if you want to write me privately or put it on its own thread, I really would like to understand what it is you're saying. Thanks.



Actually, the explanation that it's because of the overuse of antibacterials is actually the most simple and the most likely. Since bacteria are living things and since all living things are subject to variation, Darwinian selection operates on bacteria just as it does everything else. Since antibiotics literally kill bacteria and do so by making various chemical tricks happen, any variation that made a bacteria more resistant to that chemical attack would cause it to leave around more descendants than others. What has been going on since we first started using antibiotics is we have been selecting for antibacterial resistance in TB, staph, e. coli, and every other bacterial pathogen we care about. We've been using antibacterials since 1940 so just over 70 years. Given the very fast generation times of most bacteria (every 24 minutes for e. coli, under ideal conditions) and the fact that bacteria are gregarious with their genes and will just share and pick them up from any old bacterial colony we should expect resistance to naturally evolve in a population. It would be remarkable if it didn't happen.

So here I have to ask which is more likely? That bacteria are subject to Darwinian selection and that introducing antibiotics into the ecology of bacteria would inevitably (and rather quickly) lead to strains of bacteria that are resistant to antibiotics OR someone for no good reason introduced antibiotic resistance into the ecology of mammal infecting bacteria *knowing* that resistance was already evolving? (It's been known that it was happening all of my adult life, I first encountered this in 1991.)


Cheers
Aj

when creating GMO food, a gene selected for antibiotic resistance is spliced into DNA of plant cells. i'm gonna copy and paste a couple things for you:

Antibiotic Resistance Marker Genes in Genetically Engineered Foods
2002-06-19

Executive Summary



No federal laws have ever been passed to govern the regulation of genetically engineered foods and crops. The regulations in place, cobbled together under existing statutes, require no mandatory pre-market or post-market health testing. When the regulations were legally challenged in the 1980s, the court found they were flawed but did not set them aside, reasoning that they were only an initial effort to set policy. Instead, the regulations remain largely in place, although weakened over time. One result of this lax oversight is that potentially unsafe practices, such as the inclusion of antibiotic resistance marker genes, have gone forward with far too little scientific and public debate and scrutiny.

Many genetically engineered crops on the market currently contain antibiotic resistance marker genes because of the imprecision of the gene insertion process. Scientists use these genes to determine whether a gene has inserted itself into a target organism. As a result of incorporating these antibiotic resistance genes, these crops threaten the already growing problem of antibiotic resistance, which the world medical community acknowledges as a serious public health concern. Infectious diseases are responsible for one-quarter of all the deaths in the world, second only to cardiovascular diseases. As new strains of bacteria and viruses emerge that are resistant to drugs and antibiotics, infections become more difficult to treat.

The market for genetically engineered crops hinges in large part upon their acceptance by food processors. Food companies such as Kraft Foods, the largest food company in the United States and the second largest in the world, can join the call for an end to antibiotic resistance marker genes and tell biotechnology companies they do not want to put their customers at risk. Corporations have set a precedent for this type of action: McDonald's and other large corporate consumers of chicken have played a significant role in reducing in the use of antibiotics fed to chickens for non-therapeutic purposes. If food processors, as potential customers, clearly articulate that antibiotic resistance marker genes are unacceptable, manufacturers will have no incentive to continue their use.

Antibiotic resistance marker genes are just one example of how genetically engineered crops should be better regulated, so products that should never make it to market do not, and health concerns are addressed before, not after, products are commercialized. In order to accomplish this goal with regards to antibiotic resistance marker genes, products on the market with them should be removed, and no new products should be approved that contain antibiotic resistance marker genes. In addition, the state Public Interest Research Groups, along with our coalition partners in Genetically Engineered Food Alert, have issued the following call to action:

Genetically engineered food ingredients or crops should not be allowed on the market unless:

1) Independent safety testing demonstrates they have no harmful effects on human health or the environment,
2) They are labeled to ensure the consumer's right to know, and
3) The biotechnology corporations that manufacture them are held responsible for any harm.



~and to answer the technical questions (and thanks i know what a phage is lol!)


Horizontal gene transfer

Horizontal gene transfer has been reported between distantly related bacteria, and from bacteria to
yeast, mammalian cells and plant cells.
The few examples of transfer from plants to bacteria indicated by DNA sequence comparisons and
the lack of experimental confirmation suggest that the frequency of evolutionary successful gene
transfer from plants to bacteria is extremely low. However this inference is based on a small number
of experimental studies and indications in the scientific literature.
Detection of horizontal gene transfer events is difficult due to the limitations of the techniques
available. Unequivocal proof requires isolation of the putative transformed bacteria for thorough
genetic characterisation.
The rate of gene transfer from plants to bacteria is insignificant compared to gene transfer between
micro-organisms. Almost any type of bacterium has the potential to transfer DNA to any other type
of bacterium if it contains a broad host range gene transfer element.

Antibiotic resistance genes and human health

The presence of the antibiotic resistance gene by itself is not associated with any adverse health
effects.
There is in vitro evidence that free DNA in human saliva is capable of transforming a naturally
competent human oral bacterium (Mercer et al, 1999). Since the regions preceding the stomach are
likely to have the highest concentrations of intact DNA entering with the diet further research is
needed to establish whether transformation of oral bacteria occurs at significant frequencies in vivo.
Although most ingested DNA is likely to be degraded and diluted in the human gastro-intestinal
tract, natural transformation of gut epithelial cells or micro-organisms cannot be completely ruled
out.
Research in mice indicates that DNA can survive digestion and uptake by gut epithelial cells occurs,
however at levels of DNA intake unlikely to be encountered in a normal diet (Schubbert et al, 1997).
The mechanism of DNA uptake by gut epithelial cells is unknown and its significance is unclear.
If DNA uptake does occur in humans critical factors are the presence of regulatory sequences that
allow gene expression and the presence of selective pressure. Without selective pressure it is highly.......

......blahblahblah.....i can attach that entire pdf to your email if you like.


i understand that by the act of processing foods...let's take a box of Cheez-Its for example (a common GMO containing food)....clearly bacterias and therefore their DNA would not survive the process of the making of a Cheez-It. so the bacteria itself dies, but where does the DNA litter go? also, GMO food products are being fed to our meat supply, while simultaneously being fed antibiotics or being injected. (actually i think it's strictly in the feed now cuz injections are too expensive) we then, eat that meat, and not always overly well done. to me, it seems like the bacteria or even the DNA litter of said bacteria were to survive it would be here. however, stranger things have happened.