Kategorie: News
When Microbes Talk to Their Host…
Marine sponges are among the oldest animal phyla on Earth and have lived in all the world’s oceans for hundreds of millions of years. They continuously pump large amounts of water through their bodies to filter out food particles - and in doing so, they harbor an enormous number of microbes: These can account for up to 35 percent of a sponge’s weight.
A new study now shows that one of these commensals has a much more varied diet than scientists previously assumed: Ammonia-oxidizing archaea are among the most important partners of many sponges. They perform a sort of “garbage collection” function within the sponge’s tissue by removing ammonia, a metabolic byproduct that is toxic to the sponges. For decades, researchers assumed that these microbes fed exclusively on inorganic compounds such as ammonia while fixing CO₂ - a very limited, specialized diet.
A team led by Bettina Glasl and Katharina Kitzinger from the Center for Microbiology and Environmental Systems Science (CeMESS) at the University of Vienna has now refuted this view. Using the tropical elephant-ear sponge Ianthella basta and its symbiont Nitrosospongia ianthellae as examples, the team - in collaboration with partners from the Australian Institute of Marine Science - was able to demonstrate that: Archaea also take up amino acids such as valine, leucine, and isoleucine - and can even produce them themselves.
Visualized at the single-cell level
This discovery was made possible by a combination of state-of-the-art chemical and microscopic imaging techniques, including the so-called NanoSIMS technique. This allowed the team to track the metabolism of individual symbiont cells directly within their sponge host. “The major challenge was to identify which specific cells within the sponge take up the amino acids,” explains Kitzinger, co-lead author of the study and a specialist in single-cell analysis. “We were able to see how the labeled amino acids were incorporated into individual symbiont cells. This allowed us to directly link a cell’s identity to its function, rather than relying solely on predictions based on the genome.”
A Possible Form of Communication Between Microbe and Host
Particularly interesting: Because the archaea not only take up the relevant amino acids but can also produce them themselves, they could specifically influence their availability in the sponge tissue. Since such branched-chain amino acids often serve as signaling molecules, the research team suspects a possible communication function between the microbe and the animal host. “This could be a form of communication between microbes and animal hosts whose roots lie deep in evolution,” said Glasl in a press release from the University of Vienna.
Nitrosospongia ianthellae is also a special case for another reason: Within the elephant-ear sponge, this organism is solely responsible for all ammonia oxidation, whereas the sponge itself - unlike many related species - does not harbor any additional nitrite-oxidizing microbes. This makes the system particularly well-suited for studying the metabolic processes of individual symbiotic cells in isolation.
The findings thus shed new light on one of the oldest known animal-microbe symbioses on Earth:
What was long considered a simple detoxification mechanism may in fact be a significantly more complex biochemical interplay - with potential signaling functions that have simply been overlooked until now.
Further information:
science.ORF.at
University of Vienna
phys.org
Science Advances