Cell death shines a light on the origins of complex life

Organelles continue to thrive after the cells within which they exist die, a team of University of Bristol scientists have found, overturning previous assumptions that organelles decay too quickly to be fossilised. As described in the journal Sciences Advances today [27 January], researchers from Bristol's School of Earth Sciences were able to document the decay process of eukaryotic algal cells, showing that nuclei, chloroplasts and pyrenoids (organelles found within chloroplasts) can persist for weeks and months after cell death in eukaryote cells, long enough to be preserved as fossils. Emily Carlisle, a PhD candidate from Bristol's School of Earth Sciences and co-author, was able to characterise the transformation of the organelles into something resembling snot. She said: "I spent several weeks photographing algal cells as they decayed, checking the condition of the nuclei, chloroplasts and pyrenoids. From this, we could tell that these organelles don't decay immediately after cell death, but actually take many weeks to dissolve.' When life first appeared on Earth it was limited to simple bacteria. Two billion years later, complex life emerged in the form of large eukaryote cells with membrane-bound organelles, such as a nucleus and chloroplasts. The evolution of fungi, plants and animals followed.