Detailed characterization of the Arthrospira type species separating commercially grown taxa into the new genus Limnospira (Cyanobacteria)

Abstract

The genus Arthrospira has a long history of being used as a food source in different parts of the world. Its mass cultivation for production of food supplements and additives has contributed to a more detailed study of several species of this genus. In contrast, the type species of the genus (A. jenneri), has scarcely been studied. This work adopts a polyphasic approach to thoroughly investigate environmental samples of A. jenneri, whose persistent bloom was noticed in an urban reservoir in Poland, Central Europe. The obtained results were compared with strains designated as A. platensis, A. maxima, and A. fusiformis from several culture collections and other Arthrospira records from GenBank. The comparison has shown that A. jenneri differs from popular species that are massively utilized commercially with regard to its cell morphology, ultrastructure and ecology, as well as its 16S rRNA gene sequence. Based on our findings, we propose the establishment of a new genus, Limnospira, which currently encompasses three species including the massively produced L. (A.) fusiformis and L. (A.) maxima with the type species Limnospira fusiformis.

Taxonomy and Species Delimitation in Cyanobacteria

“…The species name of the most commonly cultivated spirulina is generally considered to be A. platensis Gomont. After Nowicka-Krawczyk et al [33], however, this species would be a benthic organism first described in Uruguay, while most commonly cultivated spirulina would be only the planktonic A. fusiformis (Voronichin) Komárek & Lund and A. maxima Setchell & Gardner (both later assigned to genus Limnospira by Nowicka-Krawczyk et al [33]). Genus Spirulina Turpin has been shown to be separated from Arthrospira already by Komárek and Anagnostidis [2], Castenholz et al [34] and Komárek and Lund [35] -among others-, despite some common morphological feature (namely, the coiled shape of the thallus) shared by many species belonging to one or the other of the two genera.…”

“…1B), while A. maxima is described with a thallus width about the double of A. platensis [36]. Recently, Nowicka-Krawczyk et al [33] reevaluated the type of genus Arthrospira, that is A. jenneri Stizenberger ex Gomont, arriving at the conclusion, on the basis of molecular data, that the cultivated species of Arthrospira (A. platensis, A. fusiformis and A. maxima) show enough genetic distance with respect to A. jenneri, to deserve the inclusion in a newly described genus, Limnospira, containing the species L. fusiformis and L. maxima, with the type species being L. fusiformis. A few months later, Papapanagiotou and Gkelis [37], in order to determine the taxonomic relationships among the existing Arthrospira strains (including in it Limnospira), investigated their phylogenetic relationships with a combined analysis of molecular (16S rRNA, 16S-23S rRNA ITS, and cpcBA-IGS sequences) and phenotypic (13 morphological and morphometric characters), arriving at the conclusion that Arthrospira strains may be divided into three clusters/taxa as subspecies of a single species of genus Arthrospira.…”

“…Living samples and semi-thin sections were observed with a Leica microscope DM RB Fluo. traditionally associated with species cultivated as food source, for production of local dishes as dihé in Africa or tecuitlatl in Mexico [31][32][33]. Arthrospira and Limnospira together account for 23 species, most of them of freshwater [33,2].…”

“…As an example, the recent separation of genus Limnospira from Arthrospira was based on the differences observed between the cultivated species of Arthrospira (then Limnospira) with respect to the type species of Arthrospira, that is A. jenneri [33]. However, the observations were neither done on a typus (herbarium sample or slide) of A. jenneri, either on a sample collected in the locus classicus, but rather on a collection of apparently the same organism in an urban reservoir in Poland.…”

Ecophysiology of a successful phytoplankton competitor in the African flamingo lakes: the green alga Picocystis salinarum (Picocystophyceae)

“…The Lesser Flamingo (Phoeniconaias minor Geoffroy Saint-Hilaire 1798) is the flagship species of these habitats (Childress et al 2008). The main food resource of these birds is the spirally twisted cyanobacterium, Limnospira fusiformis (Voronichin) Nowicka-Krawczyk, Mühlsteinová & Hauer (Nowicka-Krawczyk et al 2019), syn. Arthrospira fusiformis (Voronichin) Komárek & J.W.G.…”