And it's true that the specific bacteria that causes chlamydia typically depend on interactions with other organisms to survive.
So when a team of researchers discovered several new chlamydia-related species deep below the Arctic Ocean, in a place with no oxygen and without an apparent host organism, they were surprised.
"Finding Chlamydiae in this environment was completely unexpected, and of course begged the question what on earth were they doing there?" Jennah Dharamshi, a PhD student at Uppsala University in Sweden and the lead author of a recent study, said in a news release.
The findings, published last week in Current Biology, could shed new light on how chlamydia came to infect humans and other animals.
They came across a number of diverse cousins of chlamydia between 0.1 and 9.4 meters below the seafloor, and found that the new species were closely related to the bacteria that cause infections in humans and other animals.
Bacteria 'exceptionally abundant'
While the authors didn't find other host organisms that the new chlamydia-related bacteria depended on to survive, they said that the species could be getting fuel from other microorganisms deep in the ocean sediment.