The team members went through a process of gradually identifying the elements and molecules that the bacterial strain may grow. They already knew it could use oxygen, so they tested other combinations in the lab. When oxygen is not present, RSW1 can process hydrogen and elemental sulfur—the chemicals will discover the injection of volcanic vents—and create hydrogen sulfide as a product. However, although cells are technically alive in this state, they do not grow or replicate. They are exerting a small amount of energy – enough to keep alive, that’s it. “The cell is just sitting there and spinning the wheels without getting any real metabolism or biomass,” Boyd said.
The team then added the oxygen back to the mixture. As expected, bacteria grow faster. But to the researchers’ surprise, RSW1 still produces hydrogen sulfide gas, as if it was breathing on anaerobic. In fact, bacteria appear to breathe both aerobic and anaerobic and benefit from the energy of both processes. This double breathing goes a step further than previous reports: The cell not only produces sulfides in the presence of oxygen, but also performs both conflicting processes simultaneously. Bacteria shouldn’t do this at all.
Boyd said: “That put us on the road of ‘Okay, what the hell is going on here?’?”
Two ways of breathing
RSW1 appears to have hybrid metabolism while running aerobic-based sulfur modes while using oxygen to run aerobic exercise.
“The organisms are able to bridge both metabolisms are very unique.” Ranjani Muralian environmental microbiologist at the University of Nevada, Las Vegas, was not involved in the research. She said that usually when anaerobic organisms are exposed to oxygen, destructive molecules called reactive oxygen compounds create stress. “Because that doesn’t happen is really fun.”
On the west side of the thermal spring road in Yellowstone National Park (left), researchers isolated an abnormal microorganism from the gray biofilm (right).Photo: Eric Boyd; Quanta Magazine
Boyd’s team observed that bacterial growth is best when running both metabolisms simultaneously. In its unique environment, this may be an advantage: oxygen does not evenly distribute in the hot springs as long as RSW1 lives. Under changing conditions, you may bathe in oxygen for a moment before it disappears, and the hedging metabolic bet may be a highly adaptable trait.
Two ways of breathing at one time have been observed for other microorganisms: anaerobic with nitrate and aerobic exercise with oxygen. But these processes use completely different chemical pathways, and when paired, they tend to bring rich costs to microorganisms. In contrast, hybrid sulfur/oxygen metabolism of RSW1 enhances the cells rather than dragging them.
By now, this double breathing may have evaded detection. “You really have no reason to look for something like this. Plus, oxygen and sulfides react quickly to each other. He added that unless you see sulfide as a byproduct, you might miss it altogether.
Mulally said that in fact, microorganisms with double metabolism are common. She points to the presence of many habitats and organisms, where fragile gradients exist between these habitats and anaerobic areas. One example is submerged sediments that can contain cable bacteria. These elongated microorganisms in a way that one end of their body can use aerobic breathing in oxidized water, while the other end buried it deeply in the hypoxic deposits and used anaerobic breathing. Cable bacteria thrive in unstable partitions through physical separation of aerobic and anaerobic processes. But RSW1 seems to be multitasking when scrolling in spring.
How the RSW1 bacteria manage to protect their anaerobic mechanism from oxygen remains unknown. She said Murali speculated that these cells might create chemical supercomplexes internally that can surround, isolate and “clear” oxygen, she said – once it encounters it quickly, so there is no chance for the gas to interfere with sulfur-based respiration.
Boyd said RSW1 and other microorganisms with dual metabolism make you interesting models of how microbial life spans develop in large oxygenation events. “It must be a time of chaos for the microorganisms on Earth,” he said. “As the slow dripping of oxygen into the atmosphere and the ocean, any life form that can be treated with occasional brushes of new toxic gases, even for the vibrant benefits, may also be advantageous. During the transition period, two metabolisms may be better than one.
ability Reprinted with permission Quanta Magazineedit independent publications Simmons Foundation Its mission is to enhance public understanding of science by covering research developments and trends in mathematics and physics and life sciences.
