The cyanophyte Arthrospira fusiformis from Mozambique, Africa: Morphological and molecular characterization

The morphology and the Internally Transcribed Spacer sequences of two Arthrospira (Cyanobacteria) strains with tightly coiled and loosely coiled trichome, isolated from waste water treatment ponds in Maputo, Mozambique, were investigated.
According to the accepted traditional classification the tightly coiled strains were assigned as Arthrospira fusiformis and the loosely coiled as Arthrospira maxima. In both clonal cultures, initiated from a tightly coiled (strain 1) or a loosely coiled trichome (strain 2), different variants arose, in which the tightly coiled forms were more lax than the inoculated cloned trichomes, and loosely coiled forms became tightly coiled. In both cultures, different transient forms appeared, and even straight trichomes were observed.
The straight form (variant 1) was isolated and cultivated under different light intensities. After two months, this straight form had not changed into coiled trichomes. However, the trichomes obtained after growth of the hormogonia of the straight trichomes contained a mixture of loosely coiled and straight trichomes.On the basis of the morphological analysis of Arthrospira, it is evident that the degree of coiling is highly variable, which creates uncertainty when used to define the different species.
The DNA from the two clonal strains 1 and 2 was isolated and a part of the rRNA operon (including the 3' end of the 16S rRNA gene and the Internally Transcribed Spacer) was determined after amplification by PCR using specific primers. The two ITS sequences were identical and belonged to the subcluster I.A., as defined by Baurain et al. (2002). Variant 1 gave also an identical ITS sequence. A PCR to test the presence of mcyE, a gene involved in the synthesis of the microcystin synthetase, was negative for the two strains and the variant 1.
This study showed that for a reliable identification of Arthrospira species, information from specimens collected in the field, cultured strains, developmental stages, and molecular analysis, should be combined.