How to avoid DNA

By Peter Dearden 10/02/2015 12


Peter K. Dearden

 

This week I was astounded to discover this. Over 80% of a random sample of  Americans  support mandatory labelling on foods containing DNA. Ouch. Presumably everyone is worried that if you ingest DNA from a sunflower, you will become a sunflower.

So, here are my top tips for avoiding the consumption of (or indeed contact with) DNA.

  1. Don’t Eat.

Our food contains DNA. It’s kind of simple, but mashed potato contains potato DNA, beef contains cow DNA, flour contains wheat DNA. It’s really hard to think of a food which won’t contain small traces of DNA from the organisms that it is made from. Even in highly processed food there is enough DNA to be detectable . That mouthful of crisp salad, tender meat or mouth-watering chocolate then BAM – DNA.

  1. Don’t drink (even water).

Lots of drinks are made from things that had DNA, and still carry detectable DNA. Water, however should be O.K. right?  Well the problem here is microbes. Water contains microbes (even the cleanest drinking water), and those microbes contain DNA, and as soon as they hit your stomach they will start being digested and release that DNA. Even if the water is newly sterilised and you drink it from a sterilised bottle, you will pick up microbes from your mouth, fingers and lips, and then BAM – DNA.

  1. Levitate.

When it comes down to it, everything is covered in microbes – rocks, trees, dogs, toasters – all strewn with the little blighters. People too are covered in them, estimates (for which I can’t find a decent reference) suggest bacteria on/in our body outnumber our own cells 10 to 1. Don’t touch or you may inadvertently ingest some and then BAM – DNA.

  1. Don’t breathe.

Sorry folks, air also contains microbes. Lots of them. Apparently one person coming into a room adds 37 million bacteria to the air . Up to 1.8 living bacteria can be found in every litre of urban air, but even in rural and wilderness areas there are plenty . Take a deep cleansing breath of fresh country air and then BAM – DNA.

If you are avoiding DNA its probably worth mentioning that you need to eat it to produce the building blocks of your own DNA.

Joking aside, do we have a problem here? Is eating DNA a precursor to having DNA from the things we eat shoved into our cells?

Well, we have sequenced several thousand Human genomes (all the DNA in a human) and I am yet to see a report showing that there is some plant DNA inserted in one of those genomes. Cancerous cells are another popular target for DNA sequencing, and again I can’t find anything suggesting DNA from food is associated with those cells. We have really good mechanisms, mainly the digestion of food, to stop us picking up DNA from food and using it as anything but materials to make our own cells.

But what would happen if we did pick up DNA from our environment? Would we run the risk of disease or turning into what we eat? Well, while we don’t pick up DNA and stick it in our genomes, I know of one animal that does. It turns out that Bdelloid (pronounced with a silent b) rotifers have a load of DNA they have picked up from their environment shoved into their own DNA. We think this is because of the sad state of Bdelloid sex lives. Bdelloids have been asexual for at least 80 million years, reproducing without sex for a massively long time.  Biologists have been surprised by this because sexual reproduction is vital to help organisms get rid of bad mutations and defects in their DNA. Without sex, Bdelloids should have dropped dead years ago.  A few years ago, the genome of Bdelloids was sequenced, and found to have lots of bits of DNA from fungi, bacteria and plants. Indeed a follow-up study shows that about 10% of active genes in Bdelloids are borrowed. To live on borrowed time, it looks like you need to borrow DNA.

So, are Bdelloid rotifers becoming fungi, bacteria or plants because they have picked up their DNA? No, still rotifer, still Bdelloidy, for at least 80 million years.

We like to say that we are what we eat, but only in a metaphorical sense.  Eating a banana doesn’t make you one, even if you do eat banana DNA.

Bdelloidea1_w

A Bdelloid Rotifer.

 

 

 


12 Responses to “How to avoid DNA”

  • If you’re looking for a decent reference on gut microflora this (free!) article is a very good one:

    http://physrev.physiology.org/content/90/3/859 [2010-review in a top journal; already cited 427 times]

    I hope you won’t mind me indulging in quoting a few snippets:

    “Hippocrates has been quoted as saying “death sits in the bowels” and “bad digestion is the root of all evil” in 400 B.C.” [don’t let some Americans read this ;-)]

    “The human body is inhabited by a vast number of bacteria, archaea, viruses, and unicellular eukaryotes.”

    “It is estimated that the human microbiota contains as many as 10^14 bacterial cells, a number that is 10 times greater than the number of human cells present in our bodies (162, 264, 334).”

    “Estimates of the number of bacterial species present in the human gut vary widely between different studies, but it has been generally accepted that it contains ∼500 to 1,000 species (341). Nevertheless, a recent analysis involving multiple subjects has suggested that the collective human gut microbiota is composed of over 35,000 bacterial species (76).”

  • Since we’re on the off-topic topic of gut microflora, I’d like to ask a burning question I’ve been trying to find the answer to for a while:

    What percentage of the total population of gut bacteria are removed after a standard dose of broad-spectrum antibiotic? Lots of the propaganda on re-seeding gut bacteria relies on the assumption that everything dies at once. Does it?

    Also, through what route do most of the recolonising bacteria come from? Resistant survivors in the intestines, new arrivals from the oral route, or… the other route? Crudely speaking, would an enema of a sort be a viable method of reseeding the intestines or is it unnecessary due to the survival of enough bacteria in the intestines?

    Answers would be appreciated!

  • “would an enema of a sort be a viable method of reseeding the intestines” – well, a faecal transplant is one means of treating an overgrowth of the ‘nasty’ Clostridium difficile, although I remember seeing a post somewhere recently about ‘poo capsules’ to do the same via the oral route.

  • Hi Andi,

    Prof Gerald Tannock from Microbiology in Otago (and a world expert on the human microbiota) has provided the following answers to your questions. Thanks Gerald!

    The effect of certain antibiotics on the gut microbiota is not so much removing the microbiota in total, but altering the proportions of the different groups that make up the microbiota. The antibiotic may reduce the relative abundance of particular bacterial groups and this ecological change permits the increase in abundance of other types. So there are shifts in microbiota composition. Since most courses of antibiotic treatment are short term, problems do not arise. However longer term treatment with some antibiotics may open a window for the proliferation of “Cdiff” in the bowel. This bacterial species (Clostridium difficile) causes a condition called antibiotic-associated colitis, otherwise known as Cdiff infection. In some patients, this infection is difficult to cure.

    With regard to short term antibiotic treatment, research results indicate that the composition of the gut microbiota is beginning to return to the pre-antibiotic state by about one week after treatment ceases. It may not always return to exactly the way it was, probably because more than one bacterial species can do the same job (functional redundancy) in the gut.

    The regeneration of the microbiota after antibiotic treatment is considered to be from within – the restoration of the usual ecological balance between bacterial groups which is part of homeostasis.

    It seems that patients with difficult to cure Cdiff infections can be helped by enemas of faecal material from a healthy person. This treatment should only be considered in severe cases and with medical consultation.

  • To continue the theme of the microbiome, you may have seen the recent article in the NZ Herald Mum’s germs shape who we are – research http://www.nzherald.co.nz/lifestyle/news/article.cfm?c_id=6&objectid=11406897 syndicated from The Washington Post.
    The research article in Nature entitled Vertically transmitted faecal IgA levels determine extra-chromosomal phenotypic variation can be found here http://dx.doi.org/10.1038/nature14139 and is only fully-accessible for subscribers unfortunately.