Wednesday, March 16, 2016

Methanol in the Ocean: Food for the Microbes

Interesting read at Ocean News & Technology, Major Source of Methanol in the Ocean Identified:
As one of the most abundant organic compounds on the planet, methanol occurs naturally in the environment as plants release it as they grow and decompose. It is also found in the ocean, where it is a welcome food source for ravenous microbes that feast on it for energy and growth.

While scientists have long known methanol exists in the ocean, and that certain microbes love to snack on it, they’ve been stymied by one key question: where does it come from?

Researchers at the Woods Hole Oceanographic Institution (WHOI) have solved this mystery through the discovery of a massive – and previously unaccounted for – source of methanol in the ocean: phytoplankton.
“Methanol can be considered a ‘baby sugar’ molecule and is rapidly consumed in the ocean by abundant bacteria – called methylotrophs – which specialize in this type of food,” said Dr. Tracy Mincer, WHOI associate scientist and lead author of the paper. “However, up until now, the thought was that methanol in the ocean came from an overflow of terrestrial methanol in the atmosphere. So, this discovery reveals a huge source of methanol that has gone completely unaccounted for in global methanol estimates.”

Mincer first became interested in the idea of biologically-produced methanol in the ocean through previous work where he found methanol-nibbling bacteria in a phytoplankton culture he was growing. Intrigued, he extracted the microbe’s DNA and its barcodes matched up with a well-known methylotroph in the ocean.
For those who may need a refresher on methanol:
Methanol is the simplest alcohol, being only a methyl group linked to a hydroxyl group. It is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to that of ethanol (drinking alcohol). However, unlike ethanol, methanol is highly toxic and unfit for consumption. At room temperature, it is a polar liquid, and is used as an antifreeze, solvent, fuel, and as a denaturant for ethanol. It is also used for producing biodiesel via transesterification reaction.

Methanol is produced naturally in the anaerobic metabolism of many varieties of bacteria, and is commonly present in small amounts in the environment. As a result, the atmosphere contains a small amount of methanol vapor. But in only a few days, atmospheric methanol is oxidized by sunlight to produce carbon dioxide and water.

Methanol is also found in abundant quantities in star forming regions of space, and is used in astronomy as a marker for such regions.
As set out here,
Methylotrophs, in general, aerobically utilize C1 compounds by oxidizing them to yield formaldehyde. Formaldehyde, in turn, can either be "burned" for energy (by dissimilation to CO2) or assimilated into biomass, allowing the cell to grow using molecules like methanol as a sole carbon source.
Which I read as indicating that these things secrete CO2 as they burn through formaldehyde. I am prepared to be corrected on this.

If I am right, though, then we have a much larger than previously known possible natural source of carbon dioxide potentially reaching the atmosphere?

Better call the EPA.

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