Objective of this study is the isolation and identification of three strains of red algae from an environmental sample that was taken from approximately 20 Meters depth in the Mediterranean Sea in Croatia in September 2021.
The environmental sample contained mostly Corallinaceen, so it was expected that the three isolates would be the filamentous form of the coralline red algae. However, microscopic images of one of the isolates showed a spiral-like structure that would be atypical for eukaryotic algae and much rather reminiscent of the cyanobacterium Arthrospira platensis, commonly referred to as Spirulina. Arthrospira platensis has been legally admitted as a food additive in Germany for a long time. This already obtained legal status would make an introduction of a different Arthrospira strain to the food industry much less difficult than it normally is. The prospect of one of the isolates being such a Spirulina strain, one that is coloured red instead of the ubiquitous green algae, makes the identification of the two strains very interesting. In an attempt to obtain an axenic culture, the cultures were recultivated and treated with different antimicrobial substances, like antibiotics or lysozyme. To identify the algae and ascertain whether one of the isolates is an Arthrospira strain or not, and whether the three cultures contain the same strain, DNA was extracted, specific phylogenetic marker genes sequenced, and a BLAST search was performed.