An unusual partnership between single-celled algae and cyanobacteria may provide a key source of nitrogen for marine life, and could shed light on how plants evolved to have photosynthetic organelles.
Jonathan Zehr at the University of California, Santa Cruz, and his colleagues investigated a widespread cyanobacterium that lacks certain genes involved in photosynthesis and metabolism but can convert atmospheric nitrogen into forms that other organisms can use. Zehr and his team sampled sea water (pictured) to look for symbiotic partners of the bacterium, and found a kind of unicellular alga. The bacterium attaches to the cell wall of the alga, and provides it with nitrogen in exchange for carbon.
The symbiosis is probably crucial to global carbon and nitrogen cycles, and is analogous to the early stages of an evolutionary process in which plants acquired microbes that would eventually become chloroplasts, the organelles that perform photosynthesis.
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Symbiosis may fertilize seas. Nature 489, 477 (2012). https://doi.org/10.1038/489477a
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DOI: https://doi.org/10.1038/489477a
