Chlamydomonas, a single-celled green alga, has featured in work honoured by the Nobel prize for physiology or medicine awarded this month. Researchers say the organism and a light-detecting protein it carries were instrumental in experiments that helped clarify how memories, feelings and behaviour arise in the brain.
The alga steers itself toward light using a protein known as channelrhodopsin. When that protein senses light, electrically charged ions flow rapidly from outside the cell into its interior. That sudden influx generates an electrical signal that prompts the cell to swim toward the source, driven by its hair-like motor structures.
Channelrhodopsin is strikingly similar to the rhodopsin proteins found in human eyes, a resemblance that made it particularly useful to researchers studying how light detection and rapid electrical signalling can be used to probe nervous-system function. The protein’s ability to convert a light cue into an immediate electrical response provided a precise, fast-acting mechanism that could be adapted to investigate neural circuits.
The work involving Chlamydomonas and its light-sensitive channel contributed to methods that let scientists observe and manipulate patterns of electrical activity in the brain, shedding light on the circuit-level processes that underlie learning, emotion and behaviour. The Nobel recognition underlines how a simple, single-celled organism can yield tools and insights with far-reaching implications for understanding complex brain function.