Scientists have known for years that these symbiotic microorganisms serve up nitrogen to their coral hosts, but this new study sheds light on the dynamics of the process and reveals that the algae have the ability to store excess nitrogen, a capability that could help corals cope in their chronically low-nitrogen environment.
"It was a great surprise to find the nitrogen-rich crystals inside the algae," says corresponding author Anders Meibom of the École Polytechnique Fédérale de Lausanne, Switzerland. "It all makes perfect sense now. The algae suck up the ammonium and nitrate like a sponge when the concentration of these molecules increases, then store this nitrogen as uric acid crystals for later use."
Like all reef-forming corals, the species they studied, Pocillopora damicornis, is actually a symbiosis of two different organisms: the coral provides protection to a species of photosynthetic algae called dinoflagellates, which, in turn, provide sugars and nitrogen to the coral host. The symbiosis allows the coral to thrive in clear, tropical waters that are naturally nutrient-poor. In many places, however, coral reefs are suffering from an excess of nutrients - pollution from sewage and fertilizers that impacts the symbiotic relationship and the health of coral in unknown ways.
To better understand these exchanges of materials and to determine how an excess of nutrients might affect the balance, the researchers exposed pieces of coral to varying concentrations of isotopically-labeled nitrogen-rich compounds. Using the facilities at the Aquarium Tropicale Porte Dorée in Paris, France, the scientists applied a relatively new analytic technique called nano-scale secondary ion mass-spectrometry (NanoSIMS) to follow the path of the nitrogen. NanoSIMS enabled them to visualize and quantify the uptake, movement, and accumulation of this labeled nitrogen within the coral.
When supplied with nitrogen in the form of ammonium, nitrate or aspartic acid the dinoflagellates responded by rapidly storing the nitrogen as crystals of uric acid within its cells. But the dinoflagellates don't hang onto the nitrogen for long. Starting at about six hours after exposure, the microbes begin translocating nitrogen-rich compounds to the coral host, where the nitrogen is used in specific cellular compartments all over the surface layers of the coral.
This storage and release process helps explain how these corals get through the ups and downs of nitrogen concentrations, says Meibom. "This gives the coral-algae symbiosis a very efficient way to deal with strong fluctuations in nitrogen availability," writes Meibom. "When the nitrogen availability suddenly becomes high, the algae can take-up large amounts of nitrogen on a timescale of a few hours, store it into crystals inside the algae cells and then release this stored nitrogen for metabolic processes and growth when the nitrogen levels become normal again."
To follow up on this work, Meibom says he and his colleagues are now studying how carbon-based nutrients are taken up and distributed in the same coral-algae symbiosis.
This research was supported by an Advanced Grant from the European Research Council (BIOCARB) and by the Swiss National Science Foundation.
mBio® is an open access online journal published by the American Society for Microbiology to make microbiology research broadly accessible. The focus of the journal is on rapid publication of cutting-edge research spanning the entire spectrum of microbiology and related fields. It can be found online at http://mbio.asm.org.
The American Society for Microbiology is the largest single life science society, composed of over 39,000 scientists and health professionals. ASM's mission is to advance the microbiological sciences as a vehicle for understanding life processes and to apply and communicate this knowledge for the improvement of health and environmental and economic well-being worldwide.
Jim Sliwa | EurekAlert!
Signaling Pathways to the Nucleus
19.03.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau
In monogamous species, a compatible partner is more important than an ornamented one
19.03.2018 | Max-Planck-Institut für Ornithologie
For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.
In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...
Animal photoreceptors capture light with photopigments. Researchers from the University of Göttingen have now discovered that these photopigments fulfill an...
On 15 March, the AWI research aeroplane Polar 5 will depart for Greenland. Concentrating on the furthest northeast region of the island, an international team...
The world’s second-largest ice shelf was the destination for a Polarstern expedition that ended in Punta Arenas, Chile on 14th March 2018. Oceanographers from...
At the 2018 ILA Berlin Air Show from April 25–29, the Fraunhofer Institute for Laser Technology ILT is showcasing extreme high-speed Laser Material Deposition (EHLA): A video documents how for metal components that are highly loaded, EHLA has already proved itself as an alternative to hard chrome plating, which is now allowed only under special conditions.
When the EU restricted the use of hexavalent chromium compounds to special applications requiring authorization, the move prompted a rethink in the surface...
19.03.2018 | Event News
16.03.2018 | Event News
13.03.2018 | Event News
19.03.2018 | Physics and Astronomy
19.03.2018 | Materials Sciences
19.03.2018 | Event News