Molecular characterization of the toxic cyanobacterium Cylindrospermopsis raciborskii and design of a species-specific PCR

Cylindrospermopsis raciborskii is a toxic-bloom-forming cyanobacterium that is commonly found in tropical to subtropical climatic regions worldwide, b ut it is also recognized as a common component of cyanobacterial communitie s in temperate climates. Genetic profiles of C. raciborskii were examined i n 19 cultured isolates originating from geographically diverse regions of A ustralia and represented by two distinct morphotypes. A 609-bp region of rp oC1, a DNA-dependent RNA polymerase gene, was amplified by PCR from these i solates with cyanobacterium-specific primers. Sequence analysis revealed th at all isolates belonged to the same species, including morphotypes with st raight or coiled trichomes. Additional rpoC1 gene sequences obtained for a range of cyanobacteria highlighted clustering of C. raciborskii with other heterocyst-producing cyanobacteria (orders Nostocales and Stigonematales). In contrast, randomly amplified polymorphic DNA and short tandemly repeated repetitive sequence profiles revealed a greater level of genetic heterogen eity among C. raciborskii isolates than did rpoC1 gene analysis, and unique band profiles were also found among each of the cyanobacterial genera exam ined. A PCR test targeting a region of the rpoC1 gene unique to C. racibors kii was developed for the specific identification of C. raciborskii from bo th purified genomic DNA and environmental samples. The PCR was evaluated wi th a number of cyanobacterial isolates, but a PCR-positive result was only achieved with C, raciborskii. This method provides an accurate alternative to traditional morphological identification of C. raciborskii.