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Arsenic and Old Lace–Actually, Bacteria

February 24, 2019

Ultraphyte welcomes you back!

The past two years of my break from the blog have yielded ever more reasons to thank your hardworking gut bacteria. From brain control to jet lag, bacteria on their way to poop manage to control just about everything. Microbes invented us metazoans to house them—more on that in a future post. We look more like Brain Plague all the time.

Arsenic poisoning is the stuff of plays and forensics—and all too real a hazard in ground water, particularly the western USA. Chronic exposure leads to skin problems, deterioating organs, and cancers. Yet surprisingly, individuals can vary in their sensitivity. What deterimines arsenic’s effect on our bodies?

Bacteria may play a huge role. As in Brain Plague, microbial inhabitants actually do collect arsenic and protect us from it. Michael Coryell and other in Seth Walk’s lab at Montana State conducted fascinating experiments with mice. They used mice treated with antibiotics to kill much of their normal gut bacteria. The mice (plus untreated controls) were given drinking water with arsenic. (I know, those cruel scientists.) Antibiotic-treated mice excreted more arsenic in their urine than controls (a). And the antibiotic-treated mice retained more arsenic in their organs (b). Looking at the graph, the (b) result is less convincing than the excretion result, but still intriguing, especially the dramatic difference in the lungs.

How could our bacteria protect us? The bacteria metabolize arsenic—that is, they add various chemicals to it, such as sulfurs and carbons (thiols and methyl groups). Arsenic metabolism is extremely complicated, but some chemical conversions make it more soluble and less toxic, whereas other conversions do the opposite.

Even more interesting, the researchers took germ-free mice (reared in isolation from birth, like the bubble boy) and added human gut microbiota. The so-called “humanized mice” survived arsenic much better than the germ-free mice. In fact, the researchers zeroed in on one particular species, with the mouthful name of Faecalibacterium prausnitzii.

The germ-free mice survived arsenic about five days longer if they hosted this F. prausnitzii.

I still wouldn’t drink arsenic water regularly, but it’s good to know our gut residents are looking out for us—one wonders what all else they are up to.

If you’d like to reward your helpful gut friends, remember to eat some chocolate because bacteria tell us they want it.

Hope to see you at ICFA in sunny Orlando! Remember our traditional Saturday 8:00am breakfast, Clone with Joan.



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