20 Nov Biological Features
Spirulina (today its scientific name is Arthrospira) is a microscopic photosynthetic and filamentous cyanobacterium (blue-green alga) that has a long history of use as food.
It grows naturally in alkaline lakes, but for the last 25 years is commercially produced in large outdoor ponds or closed greenhouse ponds under controlled conditions.
The name Spirulina derives from the spiral or helical nature of its filaments.
Arthrospira is the scientific name of a cyanobacteria genus comprising a whole group of eatable cyanobacteria sold under the name of Spirulina.
Among the various Arthrospira species, Arthrospira platensis and Arthrospira maxima are the most important.
Arthrospira trichomes (filaments) contain one or multiples of ten cells aligned together in a straight line or more or less in spirals.
These filaments have a variable length (usually 100-200 μm) and a diameter close to 6-12 μm. The helix diameter varies from 30 to 70 μm.
The cell organization of Spirulina is typical of a prokaryote gram-negative bacterium with a lack of membrane-bound organelles.
Cell wall is surrounded by a polysaccharide envelope which is formed by four numbered layers, from the inner most outward as: LI, LII, LIII and LIV.
All these layers are very weak, except layer LII made up of peptidoglycan, substance that gives the wall its rigidity.
The protein and lipo-polysaccharide nature of the LII layer are favorite reasons for the easy human digestion of Spirulina.
The cells of Arthrospira filaments are connected by microscopic channels called plasmadesmata, like in plant cells. Spirulina cells have a number of inclusions such as thylacoid membranes with phycobilisomes, carboxysomes, ribosomes, DNA fibrils, gas vacuoles, as well as polyglucan, polyphosphate and cyanophycin granules.
The green pigment chlorophyll a, carotenes and phycobilisomes, which contain phycocyanin (blue pigment) are located in the thylakoid system (**14, **19, **20, **22).
(**) Literature on the subject