Washington, Aug 31 (IANS) The oxygen-rich waters of the oceans alone account for a maximum of four percent of Earth's methane. But now researchers have identified the cause as a bit of "weird chemistry" practiced by the most abundant microbes on the planet.
The researchers were actually exploring an unusual class of potential antibiotic agents, called phosphonates, already in use in agriculture and medicine.
Phosphonates mimic molecules the microbes use, but tend to be more resistant to enzymatic breakdown. The secret of their success is the durability of their carbon-phosphorus bond, the journal Science reported.
"We're looking at all kinds of antibiotics that have this carbon-phosphorus bond. So we found genes in a microbe that we thought would make an antibiotic. They didn't. They made something different altogether," said University of Illinois microbiology and Institute for Genomic Biology (IGB) professor William Metcalf, who led the study with chemistry and IGB professor Wilfred van der Donk.
"The microbe was Nitrosopumilus maritimus, one of the most abundant organisms on the planet and a resident of the oxygen-rich regions of the open ocean. Benjamin Griffin, postdoctoral researcher in Metcalf's lab, noticed that N. maritimus had a gene for an enzyme that resembled other enzymes involved in phosphonate biosynthesis," according to a Illinois statement.
He saw that the N. maritimus microbe also contained genes to make a molecule, called HEP. To figure out whether it was actually producing a desirable phosphonate antibiotic, chemistry postdoctoral researcher Robert Cicchillo cloned the gene for the mysterious enzyme, expressed it in a bacterium (E. coli), and ramped up production of the enzyme.
When researchers added HEP to the enzyme, the chemical reaction that ensued produced a long sought-after compound, one that could explain the origin of methane in the aerobic ocean.
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