Bioelectricity in Microalgae Cohorts

Diatoms are early Jurassic microalgae, a photosynthetic group with a major environmental role on the planet due to the biogeochemical cycling of silica and global fixation of carbon. However, they can evolve into harmful blooms through a resourceful communication mechanism, not yet fully understood. Harmful algae blooms in water supply reservoirs must be eradicated due to unwanted toxin production and filter blocking at water treatment works. Until now there has been no efficient consensus that harmful microorganisms such as diatoms communicate with each other and no accurate and self-sustained tool to monitor such communication.<br/><br/>Here, we demonstrate the ability to electrically monitor a diatom cohort. The breakthrough is realized by means of a unique measurement setup based on low impedance electrodes that exploit the large Helmholtz-Gouy-Chapman double-layer capacitance. The sensing system comprises a transducer based on a metal/Si/SiO₂/Au electrode. Small extracellular voltages of diatoms adhered to the electrode induce a displacement current that is enhanced by a gain factor proportional to the double-layer capacitance.<br/><br/>The origin is paracrine signalling, which is a feedback, or survival, mechanism that counteracts changes in the physicochemical environment. The intracellular messenger could be related to Ca²⁺ ions since spatiotemporal changes in their concentration match the characteristics of the intercellular waves. Our conclusion is supported by using a Ca²⁺ channel inhibitor. The transport of Ca²⁺ ions through the membrane to the extracellular medium is blocked and the intercellular waves disappear. The translation of microalgae cooperative signalling paves the way for early detection and prevention of harmful blooms and an extensive range of stress-induced alterations in the aquatic ecosystem.