Friend or foe? Study reveals the evolution of controversial human gut microbe

blastocystis under the microscope

Blastocystis is one of the most common microbes in the human gut, but whether it is harmful or helpful is still a matter of controversy.

Blastocystis infection could lead to diarrhoea, nausea, weight loss and fatigue, yet the microbe’s presence is also considered by some as a sign of a healthy gut.

Looking more like a soap bubble than a cell, Blastocystis has a deeply unusual appearance under the microscope. So, it was hugely surprising when it was revealed that Blastocystis is related to creatures like diatom algae, seaweeds, and the parasite that caused the Irish Potato Famine, a group united by having hallmark hair-like decorations on their cells.

To understand how Blastocystis evolved from a marine, oxygen-breathing microbe to a simplified oxygen-avoiding gut microbe, a team of nearly 20 researchers from 7 countries, co-led by Dr Anastasios Tsaousis (School of Biosciences, Kent) and Professor Joel Dacks (University of Alberta, Canada), used genome sequencing, microscopy, and cell biology to study a close relative of BlastocystisProteromonas lacertae, which lives in the gut of reptiles.

Their findings impact three important areas:

Firstly, using the genomic data and computational methods, they identified over 30 proteins potentially involved in the hallmark hair-like cellular feature, a defining point for organisms of tremendous agricultural and ecological importance.

Secondly, Proteromonas appears to have the most reduced form ever reported of the peroxisome, a cellular compartment responsible for oxygen detoxification together with the energy-generating compartment, the mitochondrion.

Finally, the data shows that Blastocystis has a metabolism more tuned to living in oxygen-poor environments than its close relative.

Together, these findings enabled a proposed general mechanism for the evolutionary changes in compartments in moving to low-oxygen environments and detail the transition of Blastocystis to its current form as one of the most prevalent parts of the human gut community.

Read the full article published in Current Biology, June 2023