Get to know the oysters that will help clean up oil spills

In the depths of the Gulf of Mexico live oysters that maintain a unique symbiosis with bacteria that live inside them. Understanding this collaboration between a bacterium and a clam could in the future help clean up oil spills.

By Racheli Vox, Angle, Science and Environment News Agency

Sometimes it seems that on our planet life can exist almost anywhere: if that In the desert, under the ice Or in the depths of the sea, it seems that you can almost always find animals, large or macroscopic, that have adapted to the unique environment in which they live and feel completely at home.

One of the environments that seem impossible for life to exist is deep in the ocean, 3,000 meters below sea level, at a depth that even the sun's rays cannot penetrate. In the southern Gulf of Mexico, in complete darkness and under tremendous pressure 300 times greater than the pressure on the surface, there exists a whole world of underwater animals that have found particularly creative ways to survive.

This area is also considered hostile compared to the ocean floor, as it is dotted with underwater volcanoes that spew asphalt. Unlike the normal volcanoes we know, which emit lava, these rare volcanoes produce oil, asphalt and natural gas - substances that are generally considered very toxic to life and plants. And in this impossible environment thrives a whole world of clams, sponges, tube worms, sea lilies and corals.

בstudy New published in the journal Nature Microbiology, the Israeli researcher Dr. Maxim Rubin-Bloom and his partners from the Max Planck Institute for Marine Microbiology in Germany discovered that survival in the harsh conditions is possible thanks to symbiosis: a situation in which different organisms live cooperatively, with at least one of the parties benefiting from it.

The special symbiosis discovered in the depths of the Gulf of Mexico is between oysters and sponges and a bacterium of the Cycloclasticus type that lives inside their bodies. The bacteria, which live inside the gill cells of the oysters, gain access to natural gas that the oysters filter out of the water with the help of their gills, which they break down and turn into carbon and energy. The oysters' side of the symbiosis is still less understood by researchers, and it is possible that they feed on materials that the bacteria created from the natural gas and spill over to them. Either way, this special symbiosis allows both oysters and sponges as well as bacteria to survive in the hostile environment.

The bacteria that breaks the rings

Beyond the extraordinary discovery, the new findings may advance research on the treatment of oil spills. In 2010, the Deepwater Horizon oil rig exploded in the Gulf of Mexico, an event that caused an ongoing oil spill, which is considered the largest environmental disaster in history. Cleaning such a leak is a long, drawn-out and complex process. One way of treatment, in which The spill in the Gulf of Mexico was used, is the use of dispersants - substances that cause the oil to break down into tiny droplets, increase its solubility in water and allow it to break down more easily. Another way is burning the oil - a controversial way due to the fact that it causes air pollution and increases the concentration of toxic substances in the bodies of fish. Another way is biological cleaning Using microorganisms, which break down the oil naturally. Various microorganisms consume oil, breaking it down into harmless substances such as fatty acids.

In the vicinity of the areas affected by the spill in the Gulf of Mexico, many Cycloclasticus bacteria were discovered, of the same species as those found in the depths of the ocean, but "free" - that do not live in symbiosis with another animal. These bacteria break down polycyclic aromatic hydrocarbons (PAH) - carcinogenic chemical compounds that are found in oil and give it, among other things, its strong smell. It is this ability that gave Cycloclasticus its name, which means "ring breaker".

Therefore, Rubin-Bloom was sure that the symbiotic bacteria he studied in the depths of the ocean would also break down these substances. However, when he exposed the oysters to mothballs, a substance you may remember from grandma's wardrobes, which is a type of aromatic hydrocarbon, it didn't move the bacteria, which didn't react at all to the substance their free-living brethren would feast on. It was discouraging, of course. "We fought and fought and in the end nothing came of it," says Robin-Bloom.

The reason for the lack of response of the symbiotic bacteria was discovered when the researchers decided to test their genome, and discovered to their surprise that the bacteria at all do not have the ability to break down aromatic hydrocarbons. On the other hand, they do know how to break down another substance that accompanies oil: natural gas. In contrast to them, the bacteria that live freely are able to decompose both the aromatic hydrocarbons and natural gas: when there is natural gas in their environment, the decomposition of which requires less energy, they prefer to decompose it, and when all that is available to them is aromatic hydrocarbons, which are more difficult to decompose, they feed on them, such as that on a hot summer day you would prefer to enjoy a seedless watermelon, but if there is only a watermelon full of black seeds in the fridge, you will probably still eat it.

In the depths of the ocean, the oysters and sponges that actively flow seawater into their bodies and filter food from them, provide the bacteria with plenty of "seedless watermelon", because thanks to the volcanoes made of asphalt, their living environment is full of a lot of natural gas that the bacteria can devour with pleasure. This is the reason why they lost the ability to break down aromatic hydrocarbons, which they no longer needed. So although the bacteria from the bottom of the sea will not be able to help us clean up oil spills, the progress in investigating the genome and understanding the function of bacteria that break down oil could help in finding ways to treat future oil spills.

Also relevant in the Mediterranean

Robin-Bloom promises to continue studying the subject. "We want to continue to explore these environments and understand more deeply the symbiosis and population composition of the bacteria that live inside the oysters and sponges. Beyond that, we know very little about the non-symbiotic cycloclastics (which live freely in the water), these are more complex populations. When there is a leak, they appear Lots of bacteria, and many researchers are engaged in understanding how these bacteria deal with oil spills.

"This work was done in the Gulf of Mexico, but we also have similar environments in Israel," emphasizes Robin-Bloom. "As part of my doctorate at the University of Haifa, we found natural gas emanations from the seabed right here in the Mediterranean Sea. There, too, we saw animals, most of which live in symbiosis with various bacteria that break down sulfur and methane gas. It is possible that at greater depths there are greater emanations of natural gas, and perhaps also of oil. So all in all it is relevant to us as well."