How Tiny Algae Shape Our World Through DMSP Biosynthesis
In the sun-dappled surface waters of the world's oceans, a microscopic molecule holds surprising sway over everything from marine ecosystems to global climate.
The unmistakable "scent of the sea" that greets you at the beach comes from an invisible gas called dimethyl sulfide (DMS). This characteristic aroma originates from one of Earth's most abundant organosulfur molecules—dimethylsulfoniopropionate, or DMSP. For decades, scientists knew marine phytoplankton produced this compound in staggering quantities, but the genetic machinery behind its creation remained a mystery.
The 2018 discovery of the DSYB enzyme marked a turning point, revealing the hidden mechanism driving a global cycle that connects marine microbiology to atmospheric processes 5 . This breakthrough not only illuminated how oceans produce billions of tonnes of DMSP annually but also provided new tools to predict which organisms are the ocean's primary producers and how they might respond to changing seas.
Dimethylsulfoniopropionate
Dimethyl Sulfide
Key Biosynthesis Enzyme
DMSP serves as a critical multi-tasker in marine environments, fulfilling several essential roles for the microorganisms that produce it:
DMSP functions as a potent antioxidant, protecting cells against damage from reactive oxygen species 1 . This is particularly important in chloroplasts and mitochondria, where ROS generation is highest.
DMSP helps phytoplankton maintain water balance and cellular integrity in saline environments 4 . Studies show that increasing salinity significantly enhances DMSP production in organisms like Prymnesium parvum.
Once released into the environment, DMSP becomes a major source of carbon and sulfur for marine bacteria, forming the basis of a microbial food web 3 .
When DMSP breaks down—either through bacterial processing or algal enzymes—it transforms into dimethyl sulfide (DMS), the volatile compound responsible for that characteristic seaside smell 5 . More importantly, DMS enters the atmosphere where it influences cloud formation and potentially global climate by serving as a source of cloud condensation nuclei 1 .
Prior to 2018, scientists faced a puzzling contradiction: eukaryotic phytoplankton were known to be the primary producers of Earth's DMSP, yet no biosynthesis genes had been identified in any such organisms 1 8 . The breakthrough came when researchers hypothesized that eukaryotic algae might use similar genetic machinery to DMSP-producing bacteria, where the dsyB gene had recently been identified 5 .
Researchers used bacterial dsyB sequences as queries to identify homologous genes in eukaryotic phytoplankton.
DSYB transcription levels correlated directly with intracellular DMSP concentrations and responded to environmental factors.
The localization of DSYB to chloroplasts and mitochondria explained how algae achieve such high intracellular DMSP concentrations—these organelles are sites of high reactive oxygen species generation, supporting DMSP's antioxidant function 5 .
To confirm DSYB's role and characteristics, researchers designed comprehensive experiments that combined genetic analysis with biochemical tracking. The work focused on the haptophyte Prymnesium parvum as a model organism.
Researchers used bacterial dsyB sequences as queries to identify homologous genes in eukaryotic phytoplankton genomes and transcriptomes 1 .
Immunogold labeling and NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) techniques pinpointed the location of DSYB proteins within algal cells 5 .
Functional tests demonstrated that DSYB exhibits MTHB methyltransferase activity, the key step in the DMSP biosynthesis transamination pathway 4 .
Scientists measured DSYB transcription levels under varying environmental conditions and correlated these with intracellular DMSP concentrations 1 .
The discovery of DSYB enabled scientists to move from estimating DMSP production through chemical measurements alone to predicting production capabilities based on genetic potential. The data reveal a remarkable story of molecular abundance and distribution.
Tonnes of DMSP produced annually 3
Of surface ocean organic carbon from DMSP 3
Intracellular DMSP concentration in some phytoplankton 4
| Organism Type | DSYB Presence | Estimated DMSP Production |
|---|---|---|
| Haptophytes | All species 4 | High |
| Dinoflagellates | Most species 4 | Very high (up to 3.4 M intracellular) 4 |
| Diatoms | ~20% of species 4 | Variable |
| Corals | Present in multiple species 1 | Significant |
| Marine Bacteria | dsyB version present 1 | Generally low |
Understanding DMSP biosynthesis required sophisticated molecular tools and techniques. Below are essential components of the methodological toolkit that enabled the DSYB discovery:
Using compatible bacterial hosts like Rhizobium to express putative DSYB genes and test for DMSP production capability 1 .
Employing isotopes like 13C and 34S to trace DMSP synthesis pathways within cells 1 .
Providing high-resolution imaging of element and isotope distribution within single cells 5 .
Screening environmental DNA sequences from ocean samples to identify and quantify DSYB genes 1 .
Functional tests demonstrating MTHB methyltransferase activity with KM values of ~88.2 µM for MTHB 4 .
The discovery of DSYB represents more than just the identification of another enzyme—it provides a powerful new lens through which to view marine microbial ecosystems.
As one researcher noted, this knowledge "will allow us to better predict which organisms are producing DMSP based on the presence of dsyB/DSYB sequences in their genomes" and "how much they are producing based on the numbers of dsyB/DSYB transcripts" 5 .
This genetic insight comes at a critical time, as oceans face unprecedented changes in temperature, acidity, and salinity. Understanding how these changes affect DSYB expression and DMSP production may help predict broader impacts on global sulfur cycling and even climate regulation.
DSYB discovery provides molecular tools to predict DMSP production capabilities in marine microorganisms.
Understanding DSYB expression helps predict impacts on global sulfur cycling and climate regulation.
Perhaps most remarkably, this discovery highlights the profound interconnectedness of life on Earth—from bacterial genes that jumped to eukaryotes eons ago, to phytoplankton whose metabolic outputs influence global atmospheric processes, to humans who detect the distant echo of this marine molecular symphony as the familiar scent of the sea.