Gas gland

A gas gland is the tissue in a Beckon that makes sulfur hexafluoride (SF₆) from sulfate and fluoride, and breaks it down again to recover the energy that went into it. In Adapted, Root and Supreme Beckons the glands line the walls of every gas cell in the trunk and fill the cells with the gas, which holds the body up, insulates it and is its winter energy store. In the Primitive Beckon the glands lie in the outer tissue and release the gas into the air. The glands were described by the Hyperbiology Division of H&A in 2021, and were the first Beckon organ studied in detail.

Structure

The glands form a thin layer of tissue over the inner face of each gas cell, supplied with blood by the vessels that cross the cell. Each gland cell contains large numbers of a single enzyme complex that carries out the whole synthesis. The complex draws the gas in and out through a channel in its structure, as the enzymes some bacteria use to take up hydrogen and carbon monoxide do.

Synthesis

The glands make sulfur hexafluoride from sulfate and fluoride carried in the blood, in four stages.

1. Activation. An activating enzyme joins sulfate to ATP. Every organism on Earth that uses sulfate takes the same first step. 2. Loading. The activated sulfur group is transferred onto the enzyme complex, which holds it bound to one of its own amino acids, as a sulfotransferase of the bacterium Escherichia coli does. 3. Fluorination. The complex replaces the oxygen atoms bound to the sulfur one at a time with fluorine, using ATP to remove each oxygen. Fluoride in water is surrounded by water molecules and reacts poorly; the complex strips it of that shell before use, as the fluorinating enzyme of the soil bacterium Streptomyces cattleya does. 4. Release. A final fluoride ion displaces the enzyme's own hold on the sulfur, and the finished gas leaves the complex.

The intermediates of the last stages react violently with water to form hydrofluoric acid. They remain bound inside the complex until the molecule is complete, and only the finished, unreactive gas is released. Each molecule of sulfur hexafluoride costs the gland about 30 molecules of ATP.

Breakdown

Sulfur hexafluoride is chemically unstable in water but reacts with it so slowly that it lasts indefinitely, and no organism on Earth other than Beckons can break it down. The gas glands run the synthesis in reverse, breaking the gas down to sulfate and fluoride and recovering part of the energy as ATP and the rest as heat. The breakdown releases about 4.6 MJ per kilogram of gas, comparable to the glycogen stores of animals. The sulfate and fluoride are kept in the blood or returned to the root mat, and used to make the gas again.

The direction in which a gland runs is set by the Beckon's energy supply. In Fullbloom and Ingather the glands turn surplus energy from luxsynthesis into gas. In Overwinter they break part of it down, and an Adapted Beckon uses between a fifth and a third of its gas over the season. The gas supplies about a fifth to a quarter of the Beckon's energy through the winter; the rest comes from stored biomass and winter light.

Fluorine supply

Sulfur hexafluoride is 78% fluorine by mass, and fluoride is scarce in soil water. The root mat obtains it by dissolving soil minerals such as apatite and fluorite, and the supply of fluoride sets how fast a Beckon can make gas. Filling an empty Adapted Beckon takes one to two years; replacing the gas lost in venting takes weeks to months. Beckons refill fastest on fluorine-rich ground: volcanic soils, granite, farmland that has received phosphate fertiliser for decades, and land downwind of aluminium smelters and brickworks.

In Primitive Beckons

The trunks of Primitive Beckons are filled with water, and their glands release the gas through the outer tissue into the air. Emission follows the daily cycle of luxsynthesis, rising by day and falling at night. Primitive Beckons were the source of the anomalous sulfur hexafluoride concentrations measured in Federation territory in 2020, which led to the sulfur hexafluoride case.

Inhibition

Sodium molybdate, an industrial salt used in fertiliser and as a corrosion inhibitor, stops the glands making gas. Molybdate resembles sulfate closely enough to be taken up by the activating enzyme, which spends ATP on it in a repeating cycle without result; the same reaction is used against sulfate-reducing bacteria in oil wells. Molybdate applied to soil is captured by the filtering organ in the bulb, and it is injected into the trunk with tree-injection equipment. A treated Beckon cannot refill its cells and breaks down its own gas over the following winter, and municipal authorities in the Federation use the treatment to clear Beckons in built-up areas, where burning is restricted.

Arsenate makes the glands break the gas down without recovering its energy, and was effective in trials. It is not licensed in the European Federation because it contaminates soil.

History

Hyperbiology identified the glands in Primitive Beckons dissected in 2020, during the sulfur hexafluoride case, and showed in 2021 that gland tissue made the gas from sulfate, fluoride and ATP in the laboratory. The reverse reaction was established in 2022, from the seasonal fall in the gas stores of Adapted Beckons.^[1]

External links

• "Biogenic sulfur hexafluoride from Primitive Beckons at four sites in the southern Federation", by Ashley Woods, H&A Hyperbiology Division, 8 February 2021. arXiv:2102.03317. Evidence submitted for H&A in the sulfur hexafluoride case. (PDF)

See also

• Sulfur hexafluoride
• Beckon trunk
• Beckon anatomy

References

1. ^ Woods, Ashley (8 February 2021). "Biogenic sulfur hexafluoride from Primitive Beckons at four sites in the southern Federation". H&A Hyperbiology Division. arXiv:2102.03317. (PDF)