In recent years, an increasing body of evidence has highlighted the significant impact of the microbiome on the host organism, influencing various essential life processes. Sponges, one of the oldest multicellular life forms on Earth, also harbor diverse microbial communities.
A team of researchers led by Assistant Professor Sergio Vargas and Professor Gert Wörheide from the Department of Earth and Environmental Sciences and the GeoBio-Center of the LMU conducted a new study published in Molecular Biology and Evolution. Their study revealed the molecular mechanisms by which sponges, specifically the model organism Lendenfeldia chondrodes, actively respond to changes in their microbiome. The researchers view these findings as evidence of a deep evolutionary history of the interaction between the host and its microbiome.
Sponges are organisms with a relatively simple structure that diverged from the rest of the animal kingdom over 600 million years ago. They possess proteins that play a role in regulating the interactions between the sponge and its microbiome, which appear to be responsible for the sponge’s ability to modify its form in response to changes in the microbiome.
“This indicates that the ability of sponges to interact with the microbiome emerged early in evolution,” explains Vargas. “However, there is still a lack of sufficient research on the underlying molecular mechanisms.” The researchers focused their investigation on the Lendenfeldia chondrodes sponge, a species frequently found in aquariums, to explore whether and how changes in the microbiome composition influence gene activity in the sponge.
Defective microbiome triggers changes in the sponge
Lendenfeldia chondrodes, a sponge species, harbors a microbiome primarily consisting of photosynthetic cyanobacteria. These sponges acquire nutrients by filtering microorganisms from the water and receive carbon compounds from their symbiotic partners. When the cyanobacteria are lost, such as due to shading, the sponges undergo significant morphological changes. In the study, blue sponges with leaf-like growth forms transformed into white, thread-like morphotypes with distinct microanatomy.
The researchers employed transcriptomic methods to demonstrate, for the first time, that these changes are accompanied by extensive alterations in gene regulation. “We observed modifications in gene activities associated with immune response and development,” notes Vargas. This suggests that sponges can detect changes in their microbiome and actively respond through developmental processes.
It is suspected that shaded sponges adjust their metabolism to compensate for the reduced supply of carbon compounds from their symbiotic partners. “Our findings emphasize the microbiome’s significance for the nutrition and development of animals in general, highlighting a long evolutionary history shared by animals and their bacterial counterparts,” adds Vargas.