The microbial communities that live in Yellowstone National Park are diverse and complex. The park is home to many fumaroles, geysers, and mud pots that heat-loving microorganisms live in and around. Scientists have made numerous discoveries there; such as identifying cyanobacteria that live on the edge of what can be endured, and revealing archaeal microbes that survive on methane.
Now, scientists have discovered bacteria at Yellowstone that can perform both aerobic and anaerobic respiration simultaneously, defying expectations. The microbes are members of the Aquificales group, and are called Hydrogenobacter. The findings have been reported in Nature Communications.
The researchers isolated this microbe from Yellowstone water samples, and were investigating what type of conditions were necessary to grow the microbes in the lab. Aquificales has previously been shown to use elemental sulfur, hydrogen and oxygen to grow. So those conditions were replicated in the lab, and the researchers watched the how the levels of sulfur and oxygen changed over time.
Cells can breathe or perform respiration with oxygen in a mechanism called aerobic respiration. But in environments that lack or are low in oxygen, cell might use some oxygen alternative in a process known as anaerobic respiration. But it was thought that cells would either use aerobic, or anaerobic respiration. They could switch back and forth from one to the other, but it was assumed cells would not do both at once. This study has upended that assumption.
Sulfide was found to be increasing while oxygen was decreasing. So the bacteria were generating sulfide in anaerobic respiration, but were also using oxygen. So both types of respiration were happening.
"There's no explanation other than that these cells are breathing oxygen at the same time that they are breathing elemental sulfur," said first study author and Montana State University graduate student Lisa Keller.
"This is really interesting, and it creates so many more questions," Keller added. "We don't know how widespread this is, but it opens the door for a lot of exploring."
This work has expanded out understanding of how cells can survive in challenging environments, and may help explain how ancient microbes adapted as the oxygenation of the Earth's environment increased after starting about 2.8 billion years ago.
