Species-Level Variability in Extracellular Production Rates of Reactive Oxygen Species by Diatoms

Area of Science:

• Marine biology
• Biogeochemistry
• Environmental science

Background:

• Reactive oxygen species (ROS), including hydrogen peroxide (H2O2) and superoxide (O2-), are biologically produced and degraded in marine systems.
• ROS are known to influence the cycling of critical elements like trace metals and carbon in oceans.

Purpose of the Study:

• To quantify extracellular production rates of H2O2 and O2- by five marine diatom species.
• To investigate the influence of light on ROS production in diatoms.
• To examine the capacity of diatoms to degrade H2O2 and O2-.

Main Methods:

• Extracellular ROS production was measured using chemiluminescence probes on filtered diatom cultures.
• ROS production was assessed in both the presence and absence of light.
• Degradation of H2O2 and O2- was evaluated by measuring recovery rates in live and killed diatom cultures.

Main Results:

• Significant variation in O2- and H2O2 production rates (up to 7.3 × 10(-16) and 3.4 × 10(-16) mol cell(-1) h(-1), respectively) was observed among diatom species.
• Light enhanced O2- production in some species, suggesting a passive photochemical pathway on cell surfaces.
• Diatom species exhibited distinct ROS production and decay mechanisms, with significant differences between live and killed cells, indicating active cellular processes.

Conclusions:

• Diatom species display diverse and species-specific extracellular ROS production and decay pathways.
• Light conditions significantly impact ROS production, with evidence of passive photochemical ROS generation.
• Active cellular processes are crucial for ROS decay, but passive mechanisms also contribute, particularly for O2-.