Bioelectricity in Diatom Phaeodactylum Tricornutum Cohorts

Diatoms are a large and highly diverse group of photosynthetic microalgae, mostly oceanic, with a major environmental role on the planet due to a significative contribution to global fixation of carbon and to the biogeochemical cycling of silica. The peculiar evolutionary history of diatoms equipped them with a unique genetic and metabolic makeup which likely contribute to their ecological success in the contemporary oceans. The presence of intracellular signaling and intercellular communication mechanisms in diatoms upon stress plays a role in the acclimatory response to (a)biotic stressors. Diatoms thrive and may proliferate into pernicious harmful algal blooms through their resourceful communication mechanisms, not yet fully understood.
We demonstrate that a population of diatoms under darkness show electrical oscillations. Cells of model diatom Phaeodactylum tricornutum were left to settle on planar gold printed electrodes. The setup was in a Faraday’s cage connected to instrumentation tailored to record minute electric fluctuations stemming from extracellular signaling. Recordings of voltage as a function of time show fast signals, preceded by voltage elevation, which resemble neurons’ “firing” action potential. The mean magnitude of these spikes was 0.0404 mV, with a mean duration of 0.444 s, they are possibly a result of collective participation of several cells as a response to voltage fluctuation. Since diatoms are not synaptically interconnected in a network as neurons are, signal transmission likely occurs by paracrine signaling, in which one cell diffuses a messenger molecule to nearby cells, causing a cascade effect by consecutive voltage-gated diffusion of ions through membrane channels. Slower signals were also recorded with a speed of 201.9 µm/s across the 1.4 mm diameter electrode, similar to previously determined for another diatom species. These signals have an atypical shape resembling random telegraph noise. Messenger Ca²⁺ ions are involved in the mechanism, since their diffusion characteristics match those of the intracellular waves.
The translation of microalgal cooperative signaling paves the way for early detection and prevention of harmful blooms and an extensive range of stress-induced alterations in the aquatic ecosystem.