An international group of scientists has discovered that a tiny ocean bacteria that is one of the most abundant microbes on Earth plays an key role in regulating the planet’s climate, according to new research published in Monday’s edition of the journal Nature Microbiology.
The organisms in question are members of the bacterial group Pelagibacterales, and they make up about 500,000 of the microbial cells found in every teaspoon of water, Dr. Ben Temperton, a bioscientist at the UK’s University of Exeter, and his colleagues explained in a statement.
Based on their work, the study authors believe that these microbes help stabilize the atmosphere by producing dimethylsulfide (DMS), an organosulfur compound that stimulates cloud formation and is an essential component to a negative feedback loop called the CLAW hypothesis.
In the CLAW hypothesis, Earth’s atmospheric temperature is stabilized through a cycle where sunlight causes certain kinds of phytoplankton to become more abundant. This, in turn, causes an increase in the production of another compound, dimethylsulfoniopropionate (DMSP). When this compound is broken down by microbes, it forms DMS, which increases cloud droplets.
Enzyme responsible for process also found in other microbes
These cloud droplets reduce the amount of sunlight that hits the surface of the oceans, and based on the new research, Pelagibacterales plays an important role in this process and may potentially be used to create improved models of how DMS affects climate, Dr. Temperton explained.
The research, he noted, “shows that the Pelagibacterales are likely an important component in climate stability” and sheds new light on exactly how the bacteria produce this vital compound. “What’s is the elegance and simplicity of DMS production in the Pelagibacterales,” the doctor said. “These organisms don’t have the genetic regulatory mechanisms found in most bacteria.”
“Having evolved in nutrient-limited oceans, they have some of the smallest genomes of all free-living organisms, because small genomes take fewer resources to replicate,” Dr. Temperton said. He compared the process to “a pressure release valve” that is “always on, but only comes into play when DMSP concentrations exceed a threshold.” In these instances, the DMSP “flows down a metabolic pathway that generates DMS as a waste product.”
While such forms of kinetic regulation are not uncommon in bacteria, the researchers noted that this is the first time that one has been found to be involved in such an important biogeochemical process. In the case of the Pelagibacterales, it controls the process using a previously unknown enzyme that generates DMS – and it isn’t the only microbe to possess this particular enzyme.
“Excitingly, the way Pelagibacterales generates DMS is via a previously unknown enzyme,” said study co-author Dr. Emily Fowler, a Ph. D. student in UEA’s School of Biological Sciences at the time of the research, “and we have found that the same enzyme is present in other hugely abundant marine bacterial species. This likely means we have been vastly underestimating the microbial contribution to the production of this important gas.”
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Image credit: Ben Temperton
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