Since most of the microbes in our gut are bacteria, they tend to hog much of the microbiome research limelight. But lurking amongst the bacteria are other microbes such as single-cell eukaryotes (SCE) and viruses, which have been largely ignored until now. Doctors and scientists have previously regarded Blastocystis, among the most common gut SCEs, as a harmless commensal organism, peacefully co-existing with its bacterial neighbors. However, that could change with the publication of a new study from NUS Medicine in Microbiome demonstrating that a subtype of Blastocystis isolated from Singapore can actually harm its neighbors and its home in an insidious way.