Identification of regulatory sites in genomic DNA
Nitrogen-fixing cyanobacteria: Eat air and prosper!
How to avoid being fooled by imposters?
Nostoc is able to
protect the machinery of nitrogen-fixation from inactivation by producing
specialized cells, called heterocysts, that rigorously exclude oxygen from
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.
Filament of Nostoc. The green cells are photosynthetic vegetative cells. The pale cell is a heterocyst, specialized for nitrogen fixation.
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.