Sugars That Glow Could Explain Ocean Carbon Mysteries

Scientists have created a glowing molecular probe that lets them watch marine microbes digest sugars in real time. This breakthrough tool reveals how algae and bacteria interact in the ocean and how carbon moves through marine ecosystems.

By lighting up when sugars are broken down, the probe exposes which microbes can consume specific complex carbohydrates and how this affects carbon storage on the seafloor. The discovery opens a new window into understanding the ocean’s carbon cycle and the microscopic processes that shape our planet’s climate.

Illuminating Ocean Chemistry

A group of chemists, microbiologists, and ecologists has created a molecular probe (a molecule designed to detect e.g. proteins or DNA inside an organism) that glows when a sugar is broken down. In their report in JACS, the researchers explain how this probe allows them to observe the tiny but crucial struggle between algae and the microbes that feed on their sugars in ocean environments.

“Sug­ars are ubi­quit­ous in mar­ine eco­sys­tems, yet it’s still un­clear whether or how mi­crobes can de­grade them all,” says Jan-Hendrik Hehem­ann from the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy and the MARUM – Cen­ter for Mar­ine En­vir­on­mental Sci­ences, both loc­ated in Bre­men. “The new probe al­lows us to watch it hap­pen live,” Peter See­ber­ger from the Max Planck In­sti­tute of Col­loids and In­ter­faces adds.

Sugars Capture Carbon in the Deep

Algae absorb carbon dioxide and turn it into oxygen and organic matter, with sugars serving as a major part of this process. However, not every sugar is easy to break down. Some are so complex that only a few microbes have the right tools to digest them. As a result, some of this carbon sinks to the ocean floor, where it can remain trapped for centuries until the proper enzymes appear.

Scientists have long tried to determine which microbes can digest which sugars, a puzzle made difficult by the enormous diversity of marine microbial communities.

Lighting Up Sugar Breakdown With FRET Technology

To tackle this challenge, the team used automated glycan assembly to produce a sugar tagged with two fluorescent dyes. These dyes interact through a process known as Förster resonance energy transfer (FRET), working together like a molecular switch. When the sugar molecule is intact, the probe stays dark. Once an enzyme cuts through the sugar’s backbone, the probe begins to glow. This reaction lets scientists see exactly where and when sugar degradation is taking place.

The team tested the tool by following the breakdown of α-mannan, a polysaccharide (long sugar chain) commonly found in algal blooms. The probe functioned successfully across multiple test systems, including purified enzymes, bacterial extracts, living cultures, and full microbial communities.

“This re­search is a won­der­ful ex­ample of in­ter­dis­cip­lin­ary col­lab­or­a­tion between Max Planck In­sti­tutes. With our FRET glycans, we now have a new tool for re­search­ing phyto­plank­ton-bac­terioplank­ton in­ter­ac­tions in the ocean,” says Rudolf Amann from the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy.

Revealing Hidden Degraders and Carbon Cycle Secrets

By en­abling the track­ing of α-man­nan turnover, this glycan probe opens up new av­en­ues for study­ing mi­cro­bial meta­bol­ism without the need for prior ge­n­omic know­ledge. Re­search­ers can now pin­point act­ive de­graders in situ, map the pro­gres­sion of glycan break­down through space and time, and quantify turnover rates in com­plex com­munit­ies.

This tool paves the way for deeper in­sights into glycan cyc­ling across eco­sys­tems, from ocean algal blooms to the hu­man gut. By ob­serving which mi­crobes are ac­tiv­ated and un­der what con­di­tions, sci­ent­ists can link spe­cific en­zymatic activ­it­ies to en­vir­on­mental pro­cesses and ul­ti­mately gain a bet­ter un­der­stand­ing of car­bon flux in the ocean.

“Sug­ars are cent­ral to the mar­ine car­bon cycle,” con­cludes first au­thor Conor Craw­ford from the Max Planck In­sti­tute of Col­loids and In­ter­faces. “With this FRET probe, we can ask: Who’s eat­ing what, where, and when?”

Reference: “Activity-Based Tracking of Glycan Turnover in Microbiomes” by Conor J. Crawford, Greta Reintjes, Vipul Solanki, Manuel G. Ricardo, Jens Harder, Rudolf Amann, Jan-Hendrik Hehemann and Peter H. Seeberger, 8 July 2025, Journal of the American Chemical Society.
DOI: 10.1021/jacs.5c07546

Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.