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Study finds Chlamydia-like bacteria in Great Barrier Reef corals

In a groundbreaking study published in the journal Science Advances, a team of researchers has made a fascinating discovery about the microbiome of corals in the Great Barrier Reef. The scientists unearthed the presence of a Chlamydia-like bacteria in these underwater ecosystems. 

The research not only adds another layer to our understanding of the coral microbiome but also sheds new light on the complex factors affecting the health of coral reefs. The team was led by the University of Melbourne, in collaboration with the Australian Institute of Marine Science and the University of Vienna, 

The researchers identified two distinct types of bacteria clusters nestled inside the tissues of the coral. One of these is a close relative of the bacterium causing chlamydia (Chlamydiales), an infection typically found in mammals. Until now, its existence within coral has been unknown.

“The novel Chlamydiales exhibit many similarities with mammalian pathogens, but we are unsure if they are detrimental or beneficial to corals. There is a possibility that this bacterium gets nutrients and energy from other coral-associated bacteria,” explained Dr. Justin Maire, lead researcher from the Faculty of Science at the University of Melbourne. 

Dr. Maire, together with Chlamydiales specialists Dr. Astrid Collingro and Professor Matthias Horn from the University of Vienna, made this discovery. “The possibility that the bacteria living inside coral tissues are interacting with each other is quite thrilling,” said the experts. 

This discovery is significant as it could unlock potential pathways to improve the resilience of corals and consequently, their survival rates. 

In addition to the Chlamydia-like bacteria, the research team found a second type of bacterium called Endozoicomonas within the coral tissues. This bacterium is known to be widespread in corals, and is generally considered beneficial. Endozoicomonas can produce B vitamins and antimicrobial compounds, which are essential for the coral’s health.

“One of the focus areas in my lab is the development of bacterial probiotics for corals, helping to improve their resistance to thermal stress and survival rates caused by climate warming,” said study senior author Professor Madeleine van Oppen of the University of Melbourne.

Despite the crucial role of bacteria in maintaining coral health, our understanding of coral-associated bacteria remains limited. This new research opens up avenues for further exploration. 

“We still know very little about the functions of coral-associated bacteria, and this new study will help us to figure out whether probiotics are a feasible solution and if bacteria such as Endozoicomonas are best placed to do the job,” said Professor van Oppen.

Understanding more about coral microbiomes and the intricate bacterial interplay within them could pave the way for innovative solutions in the face of climate change threats to these delicate marine ecosystems. 

Such discoveries underscore the importance of continued research in this field and the need for strategies that leverage the corals’ own microbiomes to promote their resilience and survival.

More about the health of coral reefs

Coral reefs, often described as the “rainforests of the sea,” are some of the most diverse and valuable ecosystems on Earth. 

They provide habitat for a multitude of marine species, protect coastlines from storms and erosion, and support human economies through tourism and fisheries. However, the health of these critical ecosystems is currently under significant threat from numerous fronts, both natural and human-induced.

One primary concern is the phenomenon of coral bleaching, a stress response caused mainly by warmer water temperatures resulting from climate change. 

When corals are stressed, they expel the symbiotic algae living in their tissues, causing them to turn completely white or “bleached.” These algae provide the coral with the majority of their energy through photosynthesis. Without them, the corals can starve, resulting in substantial loss of coral populations.

Apart from climate change, coral reefs also face threats from overfishing, which disrupts the balance of the coral reef ecosystem, and pollution, particularly from agricultural runoff and plastics. 

These pollutants can smother corals or lead to disease outbreaks in coral populations. Furthermore, certain types of fishing, like cyanide fishing and blast fishing, can directly destroy reefs.

Another threat is ocean acidification, a side effect of increased carbon dioxide in the atmosphere. As the ocean absorbs more carbon dioxide, the water becomes more acidic, which can negatively impact the calcification process that corals use to build their skeletal structure.

However, recent research like the Melbourne study provides hope. By understanding more about the microbiome of corals – the community of microorganisms living within and on corals – scientists can potentially find ways to improve coral resilience. 

As described in the study, the discovery of Chlamydia-like bacteria and Endozoicomonas in corals is an important step towards this goal. It not only deepens our understanding of the coral microbiome but also could pave the way for the development of bacterial probiotics that could strengthen coral resistance to thermal stress and disease.

While coral reefs are currently facing significant challenges to their health and survival, research into their biology and microbiome offers promising avenues for their conservation and restoration. 

Continued research, reducing greenhouse gas emissions, responsible fishing practices, and minimizing pollution can all play a part in preserving these vital marine ecosystems for future generations.


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