4 ms·

Scientists bust myth that our bodies have more bacteria than human cells

21 points by etiam 11y ago

toufka 11y ago
So there are 39 trillion bacterial cells in a human body, and ~30 trillion 'human' cells in our body. EXCEPT that 25 of the 30 trillion human cells in our body don't even have any human DNA in them (red blood cells lack a nucleus, cannot divide, and do not contain human genetic information). So depending on how you draw the line there are 39 trillion non-human nuclei in a human body, and only 5 trillion human nuclei. That brings our non-human:human genetic ratio right back to 10:1. Though that too is misleading given the amount of DNA in each of those nuclei. (human cells have significantly more DNA in their genome than bacterial cells) These headlines are ridiculous.
- InclinedPlane 11y ago
  Bacteria don't have nuclei. Also, you could enlist the population of mitochondria to weigh against bacteria if you really wanted to.
  - jhbadger 11y ago
    "Bacteria don't have nuclei" isn't the same thing as eukaryotic cells not having nuclei, though, as they still are functional cells with genes. The point isn't the presence or absence of a morphological feature, it is that eukaryotic cells lacking nuclei are hardly even cells, as they lack DNA entirely. As for the mitochondria, why would they be "against" bacteria? They are the enslaved proletariat of the bacterial kingdom! When the revolution comes, eukaryotes will be screwed.
  - rossdavidh 11y ago
    True, but bacteria have an analogous nucleoid, which contains genetic information. Also, the mitochondria have a lot less genetic information than the cells. More to the point about ridiculous headlines, the ratio of 10:1 is easily within the possibilities, given the uncertainty in both estimates.
  - toufka 11y ago
    Yep - you're correct, bacteria do not have a nucleus either. I was swapping the words around to try and create a parallel sentence and I thought I had corrected 'nuclei' to 'genomes' in my edit, but apparently I did not. "there are 39 trillion separate non-human genomes in a human body, and only 5 trillion human nuclei." And you'd be correct in pointing out that that sentence is also a little wonky. Which is the best metric? Nuclei, cells, dividable cells, base pairs, non-redundant base pairs, protein-encoding base pairs, expressed human protein, mass, species, etc? It's difficult to get the nomenclature exactly parallel between mammalian and bacterial cells, much less fungal or viral material. But that's also the point. It's tricky to compare, and shouting that one comparison is wrong is just kind of click-baity.
- deleted 11y ago
  [deleted]
timrpeterson 11y ago
Money quote at the end: > “It is good that we all now have a better estimate to quote,” says Peer Bork, a bioinformatician at the European Molecular Biology Laboratory in Heidelberg, Germany, who works on the human and other complex microbiomes. “But I don’t think it will actually have any biological significance.”
jkldotio 11y ago
"the researchers produce a ratio for microbial to human cells for the average man of 1.3:1, with a wide uncertainty" Even given a "wide uncertainty" their estimate is still on the side of the microbial cells. That hardly warrants a headline saying "scientists bust myth" as the "myth" was often just phrased as a "there are more" not as a specific ratio of 10:1.
siyer 11y ago
See also: Ed Yong in The Atlantic, who has a nice story on this that includes some rather fun sentences [1]: http://www.theatlantic.com/science/archive/2016/01/youre-probably-not-mostly-microbes/423228/ http://www.theatlantic.com/science/archive/2016/01/youre-pro... [1] Such as: "In 2014, Judah Rosner from the National Institutes of Health drew attention to this “fake fact” in a letter to Microbe magazine. More recent estimates, he noted, put the total number of human cells at anywhere from 15 trillion to 724 trillion, and the number of gut microbes at anywhere between 30 trillion and 400 trillion. Which gives a ratio that can best be expressed as ¯\_(ツ)_/¯."
lifeisstillgood 11y ago
Myths need busting when the myths are misleading. The idea hat there about as many bacteria cells in me as there are human cells in me is not misleading (whether it is less, more or order of magnitude more is not relevant) - it's the fact that I have a Eco-system of bacteria in and on me and recognising that is valuable
13of40 11y ago
Hemoglobin molecules are still only 0.04% iron though, right?
dang 11y ago
https://news.ycombinator.com/item?id=10871694 https://news.ycombinator.com/item?id=10871694

21 points by etiam 11y ago

So there are 39 trillion bacterial cells in a human body, and ~30 trillion 'human' cells in our body. EXCEPT that 25 of the 30 trillion human cells in our body don't even have any human DNA in them (red blood cells lack a nucleus, cannot divide, and do not contain human genetic information). So depending on how you draw the line there are 39 trillion non-human nuclei in a human body, and only 5 trillion human nuclei. That brings our non-human:human genetic ratio right back to 10:1. Though that too is misleading given the amount of DNA in each of those nuclei. (human cells have significantly more DNA in their genome than bacterial cells) These headlines are ridiculous.

InclinedPlane 11y ago
Bacteria don't have nuclei. Also, you could enlist the population of mitochondria to weigh against bacteria if you really wanted to.
- jhbadger 11y ago
  "Bacteria don't have nuclei" isn't the same thing as eukaryotic cells not having nuclei, though, as they still are functional cells with genes. The point isn't the presence or absence of a morphological feature, it is that eukaryotic cells lacking nuclei are hardly even cells, as they lack DNA entirely. As for the mitochondria, why would they be "against" bacteria? They are the enslaved proletariat of the bacterial kingdom! When the revolution comes, eukaryotes will be screwed.
- rossdavidh 11y ago
  True, but bacteria have an analogous nucleoid, which contains genetic information. Also, the mitochondria have a lot less genetic information than the cells. More to the point about ridiculous headlines, the ratio of 10:1 is easily within the possibilities, given the uncertainty in both estimates.
- toufka 11y ago
  Yep - you're correct, bacteria do not have a nucleus either. I was swapping the words around to try and create a parallel sentence and I thought I had corrected 'nuclei' to 'genomes' in my edit, but apparently I did not. "there are 39 trillion separate non-human genomes in a human body, and only 5 trillion human nuclei." And you'd be correct in pointing out that that sentence is also a little wonky. Which is the best metric? Nuclei, cells, dividable cells, base pairs, non-redundant base pairs, protein-encoding base pairs, expressed human protein, mass, species, etc? It's difficult to get the nomenclature exactly parallel between mammalian and bacterial cells, much less fungal or viral material. But that's also the point. It's tricky to compare, and shouting that one comparison is wrong is just kind of click-baity.
deleted 11y ago
[deleted]

timrpeterson 11y ago

Money quote at the end: > “It is good that we all now have a better estimate to quote,” says Peer Bork, a bioinformatician at the European Molecular Biology Laboratory in Heidelberg, Germany, who works on the human and other complex microbiomes. “But I don’t think it will actually have any biological significance.”

jkldotio 11y ago

"the researchers produce a ratio for microbial to human cells for the average man of 1.3:1, with a wide uncertainty" Even given a "wide uncertainty" their estimate is still on the side of the microbial cells. That hardly warrants a headline saying "scientists bust myth" as the "myth" was often just phrased as a "there are more" not as a specific ratio of 10:1.

siyer 11y ago

See also: Ed Yong in The Atlantic, who has a nice story on this that includes some rather fun sentences [1]: http://www.theatlantic.com/science/archive/2016/01/youre-probably-not-mostly-microbes/423228/ http://www.theatlantic.com/science/archive/2016/01/youre-pro... [1] Such as: "In 2014, Judah Rosner from the National Institutes of Health drew attention to this “fake fact” in a letter to Microbe magazine. More recent estimates, he noted, put the total number of human cells at anywhere from 15 trillion to 724 trillion, and the number of gut microbes at anywhere between 30 trillion and 400 trillion. Which gives a ratio that can best be expressed as ¯\_(ツ)_/¯."

lifeisstillgood 11y ago

Myths need busting when the myths are misleading. The idea hat there about as many bacteria cells in me as there are human cells in me is not misleading (whether it is less, more or order of magnitude more is not relevant) - it's the fact that I have a Eco-system of bacteria in and on me and recognising that is valuable

13of40 11y ago

Hemoglobin molecules are still only 0.04% iron though, right?

dang 11y ago

https://news.ycombinator.com/item?id=10871694 https://news.ycombinator.com/item?id=10871694