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Identification of regulatory sites in genomic DNA
How to avoid being fooled by imposters?
Nitrogen-fixing cyanobacteria: Eat air and prosper!
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Certain cyanobacteria, amongst them Nostoc (or Anabaena PCC 7120, are among the only creatures on earth able to survive on CO2 as a source of carbon, N2 as a source of nitrogen, water as a source of electrons, and sunlight as a source of energy. This is quite a trick, because the process of fixing carbon with electrons from water necessarily produces O2 as a byproduct and the process of fixing N2 is irreversibly inactivated by tiny amounts of oxygen.
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Filament of Nostoc. The green cells are photosynthetic vegetative cells. The pale cell is a heterocyst, specialized for nitrogen fixation.
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Nostoc is able to
protect the machinery of nitrogen-fixation from inactivation by producing
specialized cells, called heterocysts, that rigorously exclude oxygen from
within them.
This bacterium is therefore a multicellular organism. Each cell contains the same DNA, but different cells express very different sets of genes.
How do they do that? you wonder.
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