Comment by aldoushuxley001 | Hacker News Reader

Comment by aldoushuxley001 | Hacker News Reader

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aldoushuxley001

Interesting.

I'm curious though, considering bacteria, fungal spores and viruses are always floating in the air around us to some extent, and almost all food similarily has bacteria, fungi and viruses in it (to some extent), how do you keep germfree mice, rats and pigs germfree? What are you feeding them? And what about them just being exposed to normal air?

I can't help but think of a GI tract completely devoid of bacterial and fungal cells as being a massive power vacuum essentially. And even if germfree mice, rate and pigs are born that way, wouldn't it be incredibly difficult to prevent these free-floating bacteria or fungal spores from inoculating their GI tracts? whether just through air or food?

I would love to see a study analyzing a germfree mouse, rat or pig that was kept germfree to full life as best as possible and then do an analysis on their microbiome to see if, in fact, they are germfree at the end of their life too. I'm not confident they would be.

They are kept in vinyl bubbles. The only things that enter the bubbles go through sterilization: a liquid sterilization for tubes/plasticware, etc., irradiation for food, autoclave sterilization for water and liquids. Germfree animals have been around for more than 70 years - they are actually not that hard to create in rats and mice because a fetus is sterile in utero.

> I can't help but think of a GI tract completely devoid of bacterial and fungal cells as being a massive power vacuum essentially

This is absolutely true for the right organisms. Surprisingly there are quite a few common human gut microbes that cannot colonize a germfree gut. Reasons are still not totally understood.

> I would love to see a study analyzing a germfree mouse, rat or pig that was kept germfree to full life as best as possible and then do an analysis on their microbiome to see if, in fact, they are germfree at the end of their life too. I'm not confident they would be.

This paper [0] from 1971 is a good review of the 40's and 50's work showing that germfree hosts are basically normal and can be easily maintained as sterile with proper procedure.

[0] Gordon and Pesti, The Gnotobiotic Animal as a Tool in the Study of Host Microbial Relationships, Bacteriological Reviews, 1971

This idea that you can find any multicellular organism without any dependency on another organism is without merit. One cannot achieve a "pure system." At the very least, evolution depends on variation within the genetics.

Fascinating, thanks for the reply. I always love hearing the protocols for requirements like this, makes a lot of sense tho, re: the sterilization techniques (irradiation for food, autoclave for liquids, etc.).

I'm surprised the germ-free animal models had such surprisingly normal lifespans. Thanks for the link too.

Part of me is still skeptical of the degree to which the germfree animal models are in fact germ free at the end of their lives (I'll have to do some more digging through the literature).

Seems like these germfree animal models should yield some great insights into the microbiome tho.

Just curious, what sort of projects are you working on? It's a fascinating field.

Slash, what are your opinions of all these microbiome mapping tests (e.g. Viome, etc.). I mean, our microbiomes seem to change fairly frequently such that a singular snapshot at these relatively infrequent intervals seems inadequate for most uses.

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