I read a paper yesterday that has me beside myself with excitement. (I really do need to get out more.) “Gut Protozoa: Friends or Foes of the Human Gut Microbiota?”[i] The authors argue “…that protozoa, like helminths, represent an important factor to take into account when studying the gut microbiome , and that their presence – especially considering their long coevolutionary history with humans – may be beneficial.”
Like helminths, protozoa suffer from major PR issues. (You can read more about that misleading PR in my post of a couple of weeks ago.) Unfortunately, it’s always the bad guys – or the bad gut guys – who get all the press. Just this week in fact, Giardia hit the news when scientists discovered how it causes gut issues (diarrhea, pain, flatulence, bloating, etc.).[ii] This protozoa releases proteins that mimic human cell functions to break the cells of the gut apart, and then eats the released nutrients. The bacteria of the gut then join in the food frenzy. If you don’t read to the end of the article, however, you’d miss this key point: “…about half of those who get the parasite experience no symptoms of the illness. Dr. Tyler said the difference in the severity of disease might be explained by the proportion of ‘good’ and ‘bad’ bacteria in the gut.” That is, it is those people with altered/depleted biomes – like all too many of us in the industrialized world – who get sick.
That makes sense, when you think about it. After all, like our bacteria, viruses, helminths, and so forth, protozoa have been with us for millions of years. To survive, we needed to learn to live in harmony with them. As this authors of this protozoa paper point out about recent research, “…the presence of commensal protozoa…was strongly associated with increased diversity and various shifts in composition of the gut bacterial microbiota in rural nonindustrialized populations.”
They go on to give multiple examples of commensal protozoa. Here are just a couple:
They suggest, in fact, that commensal species of protozoa, like Blastocystis, may feed on certain species of bacteria, giving the advantage to other, better kinds.
Say the authors: “…we argue that some intestinal protozoan inhabitants could play an important, yet largely unrecognized, role in shaping the gut bacterial microbiota and in maintaining the host-microbe equilibrium, and they should be considered as ‘friends’ of the human gut.”
Exciting stuff, right?!
[i] Chabe, M, Lokmer, A, Segurel, L. Gut protozoa: friends or foes of the human gut microbiota? Trends in Parasitology. 2017. 33(23):925-934.