Re-identification of “Oscillatoria simplicissima” isolated from the Vaal River, South Africa, as Planktothrix pseudagardhii

Nearly complete 16S ribosomal RNA sequences from a strain isolated in the Vaal River, South Africa, commonly identified as “Oscillatoria simplicissima sensu PIETERSE & STEYNBERG 1993”, as well as Planktothrix pseudagardhii NIVA CYA 153 were determined. Phylogenetic analysis of these species, together with P. pseudagardhii NIES 845T, Planktothrix agardhii NIES 204T and other closely related strains, showed that this South African strain of “O. simplicissima” closely clusters with P. pseudagardhii NIVA CYA 153, P. pseudagardhii NIES 845T and a group of P. pseudagardhii available on the database. A polyphasic approach was used to re-identify this isolate of “O. simplicissima”. A comparative morphological study between it and P. pseudagardhii NIVA CYA 153 revealed no clearly defined structural differences. Morphological studies indicated that cells of the “O. simplicissima” isolate have clear gas vesicles, which further suggests that it must be renamed to “Planktothrix pseudagardhii SUDA et M.M. WATANABE in SUDA et al. [Suda, S., Watanabe, M.M., Otsuka, S., Mahakahant, A., Yongmanitchai, W., Nopartnaraporn, N., Liu, Y., Day, J.G., 2002. Taxonomic revision of water-bloom-forming species of oscillatoroid cyanobacteria. International Journal of Systematic and Evolutionary Microbiology 52, 1577–1595.]”.