A Surprising Comparison of Male vs. Female Microbiomes | Hacker News Reader

A Surprising Comparison of Male vs. Female Microbiomes

ubiomeblog.com

27 pointsaccarmichael15 comments

I would think that the microbiome is so heavily influenced by one's environment (what they ingest, etc) that things like gender wouldn't matter so much. Considering that it's fairly easy to determine things like when someone traveled by simply looking at time series data of their microbiome, locality and diet would be the things that I'd expect to see differentiated.

Article concludes weaker statement as well:

"It turns out that in our dataset, there is no statistically significant difference between male microbiomes and female microbiomes. And, given a random sample, we would not be able to determine if it came from a man or a woman."

I found that completely unsurprising

It's about as unsurprising as the MythBusters finding that both men and women fart.

https://www.youtube.com/watch?v=6mNU6MFQP1k

I suspect they could do better than random chance in guessing the gender of the sample source.

Their tables show pretty big differences in the categories Actinobacteria (73% more in men) and Verrucomicrobia (88% more in women). Maybe their sample is so small even these very different averages are just attributable to random chance, but it seems they've made a conscious choice not to reveal the size of their database.

I wasn't sure. At first I would have assumed there to be a small but significant difference. The difference in hormones should create distinct environments so a bacterium that can take advantage of that difference would be more likely to occur in one sex than the other. Probably the male as female is the default sex. (Is there any species that starts as male?)

What this tells me is that animals are conservative with their hormones. Allowing arbitrary proteins to seep into our gut would be wasteful.

There's also that if we allowed bacteria to be affected by our sex hormones, that would also make our reproduction susceptible to alteration by those bacteria. Natural selection cuts the finest when it comes to the genes involved in procreation. So it should be rare to find a symbiotic organism with a sex organ. Viral organisms of course don't care if the host dies, or can't have babies.

> Is there any species that starts as male?

I remember an article about mollusks. I searched and found this: http://phys.org/news/2012-09-team-mollusk-gender-ages.html

Also, from Wikipedia, many fishes change from male to female, for example clownfish (aka Nemo): http://en.wikipedia.org/wiki/Sex_change#In_animals

Female isn't the 'default' sex. Both estrogens and androgens affect foetal development from the early stages. It's a myth, like synchronizing menstrual periods.

This article would have been more interesting if the author had explained the context which made them expect to find a gender-linked difference in the microbiomes. As someone unfamiliar with this field, the results of this study were completely unsurprising; it's exactly what I would have naively imagined to be the case.

Pie charts? Why not a histogram for each bacterial phylum plotted for men and women?

And some discussion of the statistical-significance test(s) used, since from the tables, there are some big differences in category proportions. (The text and the charts aren't clearly in agreement.)

These seem to be results for the intestinal microbiome. There might be different results for the skin microbiome, the sinus microbiome, or the vaginal microbiome.

"or the vaginal microbiome"

I'm going to go out on a limb and say that you can detect a gender difference here.

On a serious note, for better or worse it seems that 'microbiome' is often used colloquially to mean 'gut microbiome'

I won't be surprised if many new discoveries come out of the dataset uBiome is constructing simply because no one has ever collected such a dataset before. And at this scale.

My mind is also unblown.

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