Researchers have discovered bacteria closely related to chlamydia, a sexually transmitted infection in humans, on the Great Barrier Reef.
It's the first time the bacteria has been described in corals.
The team, led by the University of Melbourne, found two types of bacterial clusters in coral tissue on the reef:
- Chlamydiales: a bacteria that contains the pathogens responsible for chlamydia infections in mammals
- Endozoicomonas: a bacteria known to be widespread in corals, generally considered beneficial
Lead researcher Justin Maire said the discovery of chlamydiales was "a very surprising, but also exciting discovery".
"Chlamydia-like bacteria often pop up in datasets but have flown under the radar until now," Dr Maire said.
So, does chlamydiales hurt or help coral?
"At this stage, it is hard to say whether it does either," Dr Maire said.
"The novel Chlamydiales exhibit many similarities with mammalian pathogens, but we are unsure if they are detrimental or beneficial to corals."
He said the discovery added "another layer of complexity to the understanding of coral reef health".
"We worked with Chlamydiales specialists Dr Astrid Collingro and Professor Matthias Horn from the University of Vienna, and found that these bacteria steal nutrients and energy from their hosts to survive," Dr Maire said.
"There is a possibility that this bacterium gets nutrients and energy from other coral-associated bacteria.
"For those of us working to understand coral biology, the possibility that the bacteria living inside coral tissues are interacting with each other is quite thrilling."
The second bacterium discovery, Endozoicomonas, is known to be widespread in corals and is generally considered beneficial due to its ability to produce B vitamins and antimicrobial compounds.
"It will be very interesting to understand the exact nature of this association with further research, and especially if it has any impact (negative or positive) on coral bleaching, which is the main threat to coral reefs in Australia and around the world," Dr Maire said.
The discovery could help scientists understand the coral microbiome and its impact on coral reef health.
The Great Barrier Reef is a vast ecosystem built by millions of corals. Inside each one of those corals is an even smaller but equally complex ecosystem. This is known as the coral microbiome and is made up of thousands of microbes that help corals to grow and thrive.
The study, published in Sciences Advances last week, was undertaken in collaboration with the Australian Institute of Marine Science Townsville and the University of Vienna.
