Originally, the team were looking through the genetic strains of bacteria found within various samples of human saliva. They then stumbled across a mystery fragment of RNA, the building block of many viruses’ genetic sequences, which could not be immediately identified.
This piece of RNA had been discovered before by other research groups, but this new team managed to trace it to a novel bacterium within the saliva. Having pinpointed the culprit, they could then watch how it behaves. It turns out that it appears to live on groups of Actinomyces odontolyticus, a common bacteria whose genus members are found all over the world in a range of environments.
The parasitic TM7 attaches itself to the membrane of an A. odontolyticus bacterium, whereupon it begins sucking nutrients out of its host. Although initially tolerable, the parasite eventually viciously attacks and kills the bacterium, and towards the end of the infection, its gloopy contents appear to flood out of the holes poked in it.
- A. odontolyticus is known to contribute towards gum disease, and normally, specialized white blood cells hunt them down and consume them. However, when they are infected with TM7, these bacteria appear to be better at evading white blood cells, meaning that they ultimately make gum disease worse.
A strain of Actinomyces, the type of bacteria the new parasite infects, seen using a scanning electron microscope. GrahamColm/Wikimedia Commons; CC BY 3.0
[H/T: New Scientist]