The sponges use a precious metal to warn: beware! We are toxic
Don't look in the jar. A view of the sponge Theonella conica at a depth of 27 m at the Katsa site, Eilat (Photo: Shani Shoham)
A new study by Tel Aviv University and the Steinhardt Museum of Nature revealed that the sponges in the Gulf of Eilat developed an original way to deter predators from attacking them. The researchers identified that within the sponges there is an unprecedented concentration of the precious and toxic metal molybdenum, which is also an essential mineral for the functioning of the human body. In a second step, the researchers identified the bacterium that allows the sponge to store high concentrations of the metal in its body and the symbiosis between the two
The research was conducted under the leadership of PhD student Shani Shoham and Prof. Micah Ilan from the School of Zoology in the George S. Wise Faculty of Life Sciences, and the Steinhardt Museum of Nature at Tel Aviv University. The study was published in the prestigious journal Science Advances.
Bling Bling - be careful
Sponges are the earliest multicellular animals known to science. They are found in all marine environments, and have an important role in the continuity of the Earth's carbon, nitrogen and nitrogen cycles. A sponge processes and filters 50,000 times its body weight of sea water every day. Due to the huge amounts of water that pass through them, traces of elements may also accumulate in their bodies, and scientists are trying to better understand how they deal with toxic amounts of substances such as arsenic and molybdenum.
"Already 20 and 30 years ago, samples were taken in our laboratory from a sponge called Theonella conica, in the coral reef of Zanzibar in the Indian Ocean, and even then high concentrations of molybdenum were found in it," Shani Shoham explains. "This is a trace element that is important for the normal metabolism in the cells of all animals, including humans, and is also considered a highly sought-after metal in industry. In my research, I wanted to check whether there are such high concentrations in this sponge in the Gulf of Eilat as well."
According to Shani, this is a rare sponge, and in Eilat it is found at depths below 27 meters. "I found the sponge and analyzed its composition, and indeed the highest amount of molybdenum was found in it - more than any other organism on Earth: 46,793 micrograms per gram of dry weight."
"It is possible that the molybdenum is used by the sponge for protection, meaning that the sponge says: 'I am poisonous - don't eat me,' and in exchange for this service, the sponge does not eat the bacteria and stores it."
Shoham adds: "Like any trace element, as soon as you pass the water-soluble concentration - molybdenum becomes toxic. But you have to remember that sponges are hollow creatures, a collection of cells without organs or tissues. In this sponge, up to 40 of the body's volume is a microbiological society: bacteria, viruses and fungi that live with the sponge in symbiosis. One of these bacteria is called Entotheonella, it is very dominant in the sponge Theonella conica, and it is used As a kind of storage 'organ' of metals in the sponge, this happens inside the body of the sponge, where the bacterium stores more and more molybdenum, converting it from its soluble and toxic form to a mineral.
To the question of why he does it Shani says that there is still no definite answer. "We are not sure, it could be that the molybdenum is used by the sponge for protection, meaning that the sponge says: 'I am poisonous - don't eat me', and in return for this service, the sponge does not eat the bacteria and harbors it."
to harness the hoarding bacteria to our advantage
Molybdenum is indeed a very sought-after metal, which is mainly used for alloys (for example to strengthen steel), but according to Shani, it will be difficult to extract it from the sponges: "Although the concentrations in the sponge are very high, but if we quantify it in grams we will reach a few grams per sponge, and it must be remembered that the sponge itself is not There is aquaculture of sponges, mainly for the pharmaceutical industry, but it is not an easy business. Sponges are very pampered animals, which need specific conditions".
"On the other hand, it is definitely advisable to focus further research on the ability of the bacterium Entotheonella to store toxic metals. Several years ago, our laboratory discovered that a 'cousin' of the sponge, a sponge called Theonella swinhoei, which is common in the Gulf of Eilat, showed huge concentrations of the toxic metals arsenic and barium. Here, too, the same bacterium was found to be significantly responsible for accumulating the metals and turning them into minerals, thereby neutralizing their toxicity In the future, the bacterium could be used by us in the treatment of contaminated water sources where arsenic is a major nuisance that directly affects the health of about 200 million people around the world."
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