Posted on January 24, 2019 by biomebuzz
Earlier this week, I wrote about a couple of new articles in the lay press about helminths. When I posted this on Facebook, one of my readers commented that it reminded her of a blog post from this past November, about how the loss of our native helminths (our macrobiome) is associated with an increase in allergies.
Oddly enough, I was going to write about another really interesting paper[i] that was published this week out of the University of Pennsylvania, wherein researchers compared the microbiomes of multiple African and a United States populations. In this study, the scientists analyzed the microbiome via stool samples from 114 Africans – from Botswana and Tanzania, from 7 different populations – as well as a group from the USA. As you might expect, the results varied widely, very much based upon lifestyles (i.e. hunter-gatherer versus agropastoralist (which means a combination of agricultural and herding) etc.) but there were similarities too, which, at first surprised me – until a further potential explanation was given.
The at-first surprise result: samples from Botswanans who live in farming communities were nearly indistinguishable from people living in the Philadelphia area! The authors state: “The factors causing a shift towards western microbiome compositions remain unknown but appear to have a regional component that is not entirely due to differences in agricultural, pastoral, or hunting-gathering subsistence modes.” That is, it’s not just diet that has an effect on the microbiome. So what could cause a Botswanan’s microbiome to resemble a Philadelphia urbanite’s?!
“…the researchers hypothesize that the reasons are tied to Botswana’s comparative national wealth and access to medical care….there are groups undergoing these soft measures of industrialization that could be everything from increased access to clinical care to different kinds of foods. Antibiotic usage is something that can really change the gut microbiome, so people who have more access to that might be seeing marked shifts in their microbiome.”[ii]
Ah ha! Firstly – which the paper doesn’t address – as a country moves toward industrialization, helminths are among the first things to go. More than that though:
“To understand more about what the bacteria in the gut were actually doing, the researchers looked for molecular pathways that were abundant across the various microbial species in a given sample. In the U.S. samples, they identified pathways involved in breaking down environmental pollutants, such as bisphenol, which includes bisphenol A, better known as ‘the dreaded BPA in plastics’…as well as DDT, the insecticide responsible for thinning birds’ eggshells that has been banned in the U.S. since the 1970s. They found evidence of DDT-breakdown pathways as well in the samples from Botswana, a country that has continued to use the chemical to control mosquitoes responsible for transmitted diseases such as malaria.”
Lovely, right? (not)
As expected then, there was a big difference between the microbes of the Tanzanians, from a non-industrialized country, and the Botswanan populations. “The gut microbiomes from Tanzanian populations tended to have a higher number of microbes in each sample, and individuals tended to share similar microbial profiles. In Botswana, on the other hand, samples tended to have fewer microbial species overall, and individuals’ microbiomes tended to be more different from one another. The latter pattern was also present in the U.S. samples.”
So, once again, we see that industrialization leads to biome depletion.
This morning, I read a little report in Gut Microbiota for Health[iii], entitled “Gut Microbiota Diversity: What Can We Do to Preserve It?” For obvious reasons, that caught my attention. It describes a paper by researchers at Rutgers University “…regarding the actions that need to be taken to restore and preserve our gut microbiota for future generations.”
There were no surprises in this paper, but as it’s on topic so I’ll share some highlights:
[i] Hansen, MEB, et. al. Population structure of human gut bacteria in a diverse cohort from rural Tanzania and Botswana. Genome Biology. 2019:20:16. https://doi.org/10.1186/s13059-018-1616-9
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