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.<br/>We demonstrate that a population of diatoms under darkness show electrical oscillations. Cells of model diatom <i>Phaeodactylum tricornutum </i>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.<br/>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.