Domain – Bacteria
Phylum - Cyanobacteria
Order - Nostocales
Family - Nostocaceae
Genus - Nostoc
SpeciesN. calcicola, N. commune,
    N. cycadae, N. desertorum,
    N. edaphicum, N. ellipsosporum,
    N. entophytum, N. flagelliforme,
    N. indistinguenda, N. lichenoides,
    N. linckia, N. muscorum,
    N. paludosum, N. piscinale,
    N. punctiforme, N. sphaericum,
    N. trichormus
picture by Paul James, click for original site
First, Nostoc falls under the Domain Bacteria. It is an organism with a  prokaryotic cell structure with cell walls containing peptidogylcan. It has no internal membrane bound structures, or organelles, and the genetic material is not found within a nucleus. The Phylum Cyanobacteria is composed of photosynthetic bacteria. Nostoc then falls into the Order Nostocales because it has non-branching filiments and is futher separated into the Family Nostocaceae for having special nitrogen fixing heterocysts. Finally, we come to the Genus Nostoc, which contains organisms that form spherical colonies of filaments embedded in a gelatinous substance.
High-GC Gram Positives
Low-GC Gram Positives
Phylogenetic Tree of Domain Bacteria
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       - Watch out!  it can be a pain in the foot!