海中のスイートスポット(Sweet spots in the sea)

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海草の草原の下に膨大な量の糖分があることを発見 Researchers have discovered vast amounts of sugars underneath seagrass meadows

2022-05-02 マックス・プランク研究所

マックス・プランク海洋微生物学研究所の科学者たちは、海草が大量の砂糖、主にスクロースを土壌に放出していることを報告しました。このような高濃度の糖分は驚くべきことである。通常、微生物は環境中の遊離糖はすぐに消費してしまう。ところが、海草はフェノール化合物を排出しており、これがほとんどの微生物によるスクロースの分解を抑制していることが分かった。このため、ショ糖は草原の下に埋もれたままとなり、CO2に変換されて海や大気へ戻されることはない。

<関連情報>

海草の根圏を支配する糖類 Sugars dominate the seagrass rhizosphere

E. Maggie Sogin,Dolma Michellod,Harald R. Gruber-Vodicka,Patric Bourceau,Benedikt Geier,Dimitri V. Meier,Michael Seidel,Soeren Ahmerkamp,Sina Schorn,Grace D’Angelo,Gabriele Procaccini,Nicole Dubilier & Manuel Liebeke
Nature Ecology & Evolution  Published: 02 May 2022
DOI:https://doi.org/10.1038/s41559-022-01740-z

Abstract

Seagrasses are among the most efficient sinks of carbon dioxide on Earth. While carbon sequestration in terrestrial plants is linked to the microorganisms living in their soils, the interactions of seagrasses with their rhizospheres are poorly understood. Here, we show that the seagrass, Posidonia oceanica excretes sugars, mainly sucrose, into its rhizosphere. These sugars accumulate to µM concentrations—nearly 80 times higher than previously observed in marine environments. This finding is unexpected as sugars are readily consumed by microorganisms. Our experiments indicated that under low oxygen conditions, phenolic compounds from P. oceanica inhibited microbial consumption of sucrose. Analyses of the rhizosphere community revealed that many microbes had the genes for degrading sucrose but these were only expressed by a few taxa that also expressed genes for degrading phenolics. Given that we observed high sucrose concentrations underneath three other species of marine plants, we predict that the presence of plant-produced phenolics under low oxygen conditions allows the accumulation of labile molecules across aquatic rhizospheres.

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