Discovery opens door to potential new discoveries in the future
Sponges are important hosts for microbes, making up a significant part of the total range of microorganisms in the oceans. This was the discovery made by an international research team, led by scientists from the University of New South Wales (Australia) in collaboration with a team from GEOMAR Helmholtz Centre for Ocean Research Kiel.
Sponges are among the oldest multicellular organisms on Earth, having survived temperature extremes (e.g. the Ice Age) and several mass extinctions. Today they have colonised almost every type of habitat in the ocean, from the shallow tropical seas to the deep seas in the polar latitudes.
In a unique project, researchers from 19 scientific institutions in eight countries have proved that sponges are home to a diverse range of microbes. "We have found 40,000 different species of microorganisms in sponges," says Professor Dr Ute Hentschel Humeida from GEOMAR. She is one of the authors of the study, which was published in the journal Nature Communications.
We have long known that sponges exist alongside microbes in symbiosis. As sponges are not mobile, they cannot move away from an undesirable environment or from predators or prevent themselves from becoming overgrown with biofilm. Hence, over millions of years, sponges have developed effective symbiotic relationships with other organisms, like microbes. Some microbes help the sponges fight off illnesses or defend against predators. This is similar to our own bodies, which have microbes that support digestion or regulate the immune system, said Professor Humeida.
However, the extent of the diversity and distribution of microbes in sponges have not been known till now. For this research, over a period of four years, the research team collected more than 800 samples of sponges from the Pacific, Atlantic and Indian Ocean, as well as the Mediterranean and Red Sea. The samples were collected at three central collection points worldwide (known as "hubs"), and prepared them for further processing. Professor Humeida's team was in charge of the samples from Europe and the Arab world.
After collecting the samples, the researchers archived and processed them for high-throughput sequencing. Then the samples were sent to the laboratories of the Earth Microbiome Project in the United States. According to Professor Humeida, "Sixty-five million determinations were carried out for this study. Ten years ago, such comprehensive analysis was unimaginable."
The study uncovered a great diversity of microbial species in the sponge samples; there was even a particular sponge that was found to host 12,000 different types of microorganisms. The researchers also discovered that the sponges demonstrated a fairly consistent pattern: Regardless of where the samples originated, the occurrence and frequency of the microbes were similar in all the samples; this highlighted the long historical relationship between sponges and microbes.
This study illustrates the importance of sponges in the discovery of new medicines from marine ecosystems. Microorganisms may produce substances that can be used for medical applications, as well as the development of food ingredients or cosmetics. To conclude, Professor Humeida describes sponges as a treasure trove and we are just starting to understand them.