Award: OCE-2202723

PI: Prof. Gordon T. Taylor

Research Associate: Dr. Elena Yakubovskaya

Institution: School of Marine and Atmospheric Sciences, Stony Brook University

Project Outcomes: Extracellular vesicles (EVs) are nanoscale (30-1,000 nanometers), membrane-bound particles released by cells into their surrounding environment and can contain "infochemical cargo” (DNA, RNA, peptide, etc.). In the ocean, EVs are produced by diverse microorganisms, yet their ecological roles remain largely unknown. EVs may serve as defense, stress response, waste elimination, or communication (Fig. 1). EVs are abundant in seawater and similar in size to viruses, so they are undoubtedly collected in the operationally defined “viral-enriched size fraction” in ocean surveys (Fig. 2). These particles may represent a major but overlooked pathway for communication and material transfer between marine microbes. Understanding how EVs are formed, how their composition changes in response to stress, and how they differ from viral particles is essential to revealing their roles in plankton ecology and ocean chemical cycles.

We investigated marine EVs through two complementary approaches. First, during a 2023 expedition aboard the Research Vessel Atlantis to the Eastern Tropical North Pacific's oxygen minimum zone (OMZ), we collected large-volume seawater samples spanning depths from 10 to 600 meters. Using gentle filtration and separation techniques, nanoparticle tracking analysis, and nanoscale flow cytometry, we demonstrated that EVs are present throughout both surface and deeper waters (mesopelagic "twilight zone") at concentrations comparable to viruses (10³–10⁸ particles per milliliter). These field data provide the first systematic evidence that EVs are widespread in low-oxygen environments and reveal their heterogeneity in size and composition, especially in deeper waters.

Second, laboratory studies with pure cultures of the green microalga Tetraselmis striata allowed us to probe how environmental factors and viral infection influence EV production. Viral infection experiments with an algal virus caused a more than 100-fold increase in vesicle release within the first hours of infection. By contrast, stress treatments involving changes in nutrients, light, and temperature showed that vesicle output remained relatively stable. However, chemical analyses revealed clear shifts in EV protein and lipid cargo content.

Using nanoflow cytometry combined with fluorescent stains for DNA/RNA and membranes, we identified distinct particle pools that separated non-enveloped viral capsids from lipid-bound EVs. Targeted statistical methods further refined these distinctions, confirming that vesicle composition is heterogeneous and responsive to viral infection of hosts. Advanced imaging approaches, including Raman microspectroscopy and Atomic Force Microscopy (AFM) analyses, linked vesicle size/shape to biochemical composition at the single-particle level (Fig. 3).

Together, these approaches created a reproducible protocol for recognizing and purifying EVs in natural water samples, overcoming significant and persistent technical barriers in the field and enabling future studies of their ecological roles.

Broader Impacts: Our results show that EVs are abundant in the ocean and actively produced by microalgae in response to stress and infection, underscoring their likely importance in microbial interactions and elemental cycling. The project provided extensive training opportunities. A graduate student gained expertise in EV isolation and nanoflow cytometry. Several undergraduates contributed to culture work and data analysis. Outreach activities engaged more than 100 middle and high school students through SigmaCamp courses and a live ship-to-shore broadcast from the R/V Atlantis. Together, our efforts advanced both scientific understanding and STEM education by highlighting a previously hidden dimension of microbial communication in the sea.

Last Modified: 09/04/2025
Modified by: Gordon T Taylor