Occurrence of non-cylindrospermopsin-producing Aphanizomenon ovalisporum and Anabaena bergii in Lake Kinneret (Israel)

The cylindrospermopsin (CYN)-producing cyanobacterium Aphanizomenon ovalisporum is currently known from the Mediterranean area of Europe and the Middle East and from North America and Australia. Aphanizomenon ovalisporum was observed for the first time in Lake Kinneret (Sea of Galilee, Israel) in 1994. It appeared with an exceptional bloom and has persisted since then. To gain further insight into biodiversity and chemotype composition of this invasive cyanobacterium, we isolated, cultured and analyzed six putative A. ovalisporum strains from Lake Kinneret in 2010. In a polyphasic approach, the strains were investigated for their morphology and phylogeny (based on 16S rRNA gene and PC-IGS) as well as for CYN production [by enzyme-linked immunosorbent assay (ELISA) and LC-MS] and the presence of four fragments of the CYN-encoding gene cluster (aoaA/cyrA, aoaB/cyrB, aoaC/cyrC and cyrJ). Two isolated strains were assigned to A. ovalisporum, whereas four strains were identified as Anabaena bergii. Unlike previous reports of toxic A. ovalisporum from Lake Kinneret, all strains isolated in this study tested negative for CYN by ELISA and LC-MS. All strains contained aoaA/cyrA, aoaB/cyrB and aoaC/cyrC fragments of the CYN gene cluster. The cyrJ fragment was not detected in any of the isolated strains. This is the first report describing non-CYN-producing A. ovalisporum strains and the presence of the cyanobacterium A. bergii in L. Kinneret.