When green algae run out of air

When green algae “can’t breathe”, they get rid of excess energy through the production of hydrogen. Biologists at the Ruhr-Universität Bochum have found out how the cells notice the absence of oxygen. For this, they need the messenger molecule nitric oxide and the protein haemoglobin, which is commonly known from red blood cells of humans. With colleagues at the UC Los Angeles, the Bochum team reported in the journal PNAS.

In the human body, haemoglobin transports oxygen from the lungs to the organs and brings carbon dioxide, which is produced there, back to the lungs. “However, scientists have known for years that there is not just the one haemoglobin”, says Prof. Thomas Happe from the Work Group Photobiotechnology. Nature has produced a large number of related proteins which fulfil different functions. The green alga Chlamydomonas reinhardtii has what is known as a “truncated” haemoglobin, the function of which was previously unknown. Happe’s team has deciphered its role in surviving in an oxygen-free environment.

When Chlamydomonas has no oxygen available, the algae transfer excess electrons to protons, creating hydrogen (H2). “For this to work, the green alga activates a certain gene programme and creates many new proteins”, Happe explains. “But how exactly the cells even notice that oxygen is missing is something we did not know.” The research team looked for genes that are particularly active when green algae have to live without oxygen – and found a gene that forms the blueprint for a haemoglobin. In an oxygen-rich environment, however, this gene was completely idle. Via When green algae run out of air: Single cell organisms need haemoglobin to survive in an oxygen-free environment.

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