A team of scientists has invented a fluorescent molecular probe that lights up when marine microbes degrade sugars, revealing key processes in the ocean's carbon cycle. This tool allows real-time observation of how algae and bacteria interact in breaking down complex carbohydrates. The breakthrough, detailed in the Journal of the American Chemical Society, promises deeper insights into carbon storage and release in marine ecosystems.
In a collaborative effort involving chemists, microbiologists, and ecologists from Max Planck Institutes, researchers have developed a innovative sugar probe to visualize microbial activity in the ocean. The probe, created using automated glycan assembly, tags sugars with two fluorescent dyes that employ Förster resonance energy transfer (FRET). When intact, the dyes keep the probe dark; but as enzymes break the sugar's backbone, it emits light, enabling scientists to pinpoint degradation in real time.
Algae absorb carbon dioxide to produce oxygen and organic matter, including sugars that are central to the marine carbon cycle. However, not all sugars are easily digestible—some complex ones, like α-mannan from algal blooms, sink to the seafloor if undegraded, trapping carbon for centuries. The probe addresses this challenge by tracking such polysaccharides without needing prior genomic data.
"Sugars are ubiquitous in marine ecosystems, yet it's still unclear whether or how microbes can degrade them all," said Jan-Hendrik Hehemann from the Max Planck Institute for Marine Microbiology and the MARUM Center for Marine Environmental Sciences in Bremen. "The new probe allows us to watch it happen live," added Peter Seeberger from the Max Planck Institute of Colloids and Interfaces.
Tested successfully in purified enzymes, bacterial extracts, live cells, and complex communities, the tool maps α-mannan turnover and identifies active degraders. "This research is a wonderful example of interdisciplinary collaboration between Max Planck Institutes," noted Rudolf Amann from the Max Planck Institute for Marine Microbiology. "With our FRET glycans, we now have a new tool for researching phytoplankton-bacterioplankton interactions in the ocean."
First author Conor Crawford emphasized its potential: "Sugars are central to the marine carbon cycle. With this FRET probe, we can ask: Who's eating what, where, and when?" This advance extends beyond oceans to ecosystems like the human gut, enhancing understanding of glycan cycling and environmental carbon flux.