Heterotrophic eubacteria isolated from cultures of the cyanobacterium, spirulina maxima

Abstract

AbstractThree distinct heterotrophic eubacterial strains were isolated from mixotrophic cultures of the filamentous cyanobacterium, Spirulina maxima (Gom) Geitl. Spirulina spp. are considered to be prime candidates for the phototrophic production of biomass protein, particularly in developing countries. These cyanobacteria are extreme alkaliphiles and halophiles, making their production in arid regions promising.Most previous studies on the eubacteria which live in Spirulina culture systems have focused on determining the possible presence of pathogenic species in biomass protein. Little has been done to understand the symbiotic relationships between the cyanobacterium and its eubacterial cosymbionts. From the perspective of a heterotrophic eubacterium, autotrophic cultural systems of Spirulina have limited carbon and energy resources, being limited to cyanobacterial exudates.In this study, three eubacterial strains were isolated and studied. One strain, a Gram‐negative, non‐sporing, motile rod, grew exceptionally well in a mineral salts medium where only a small amount of a single low molecular weight organic compound (e.g., acetate) was supplied as sole energy source. This strain was also extremely euryresponsive with respect to salinity and alkalinity as well. Two less well‐adapted eubacterial strains are also described.