Spirulina cyanobacteria. Scanning electron micrograph (SEM). Spirulina is a gram negative, non-toxic species of cyanobacteria with a wide array of uses in the natural and commercial world. While many bacteria are known for their pathogenic effects, Spirulina is primarily known across the world for its potential nutritional value. It is one of the rare edible bacteria. Historically, it is known to have been regularly consumed by the Aztecs and tropical climate populations where it was often dried into flat patties for easy consumption. More recently, the consumption of this species has been shown to lower blood pressure and reduce cholesterol, which are two of the most prevalent health concerns in the modern world. Magnification: x700 when printed 10 centimetres wide.