Abstract:
In South Africa, little is known about the production of microcystin by the genus Anabaena Bory. In April 2012, during a
cyanobacterial bloom event in Theewaterskloof Dam, Western Cape province, the plankton was sampled on 10 occasions. The
dominant algae belonged to the genus Anabaena, a family of filamentous cyanobacteria known to produce cyanotoxins
such as anatoxin-a, harmful to humans and the aquatic foodweb. The specimens isolated lacked the characteristic akinetes
and/or heterocysts associated with this genus. Therefore the 16S rRNA gene was Sanger sequenced and a maximum parsimony
tree was constructed, confirming its identity as Anabaena ucrainica (Schkorbatow) M. Watanabe. Enzyme-linked
immunosorbent assay (ELISA) confirmed the presence of microcystin-LR in the isolated A. ucrainica field sample, while
PCR analysis and sequencing further confirmed the presence of mcy genes in this species. It was speculated from the
data that prevailing low water-column temperatures and strong gusty winds may have resulted in the lack of akinete or
heterocyst production. The Anabaena strain isolated from Theewaterskloof Dam is the first report of a strain containing
microcystin-LR belonging to this genus in a freshwater body in Africa.
