The presence of CYN was confirmed in 16 samples. The homology searches revealed that amplified sequences of four water samples, which were selected from among all the samples, displayed a strong 99% homology to cyrJ gene of Aphanizomenon sp. 10E6. The culture of C. raciborskii did not contain the cyrJ gene nor the CYN. The specificity of C. raciborskii

was confirmed by application of a fragment of the rpoC1. These first genetic analyses have shown that Aphanizomenon seems to be the main cyanobacterial genus responsible for the production of CYN in the Polish lakes. The lack of toxigenicity of the isolated C. raciborskii suggests that it is possible that this invasive species does not demonstrate toxigenic activity in Polish LY2157299 clinical trial water bodies. Climate change increases water temperatures and nutrient concentration and hence the intensity of eutrophication. In consequence, global warming causes massive cyanobacteria bloom in many water bodies

(Delpla et al., 2009; Nõges et al., 2011). Ultimately, cyanobacterial blooms and their toxins pose a serious threat to public health through water supply systems, recreation or agriculture, and to the natural environment. The problem of cyanobacteria responsible for the production of microcystins (MCs) belonging to the cyanobacterial hepatotoxins is common. In Poland, regular blooms with domination of microcystin-producing cyanobacteria Planktothrix agardhii or Microcystis aeruginosa find protocol and MCs concentration reaching 212.7 μg L−1 have been documented well (Pawlik-Skowrońska et al., 2008; Mankiewicz-Boczek et al., 2006; Mazur-Marzec et al., 2010). Recently, the occurrence of other cyanotoxin (representing the group of cytotoxins), cylindrospermopsin (CYN), with maximum 1.8 μg L−1, has been reported in the Western Poland (Kokociński et al., 2009). CYN is a stable alkaloid, which is able to inhibit synthesis of proteins. Liver is the main target of the CYN activity; however, other organs, such as kidneys, lungs, thymus, spleen, adrenal glands, intestinal tract, Nabilone immune system and heart, might

also be affected (Falconer, 1999; Carmichael, 2001; van Apeldoorn et al., 2007; Žegura et al., 2011). Moreover, CYN is genotoxic and probably more hazardous to human and animal health than MCs (Žegura et al., 2011). Therefore, it seems to be important not only to estimate the concentration of CYN in the water but also to determine the source of CYN to identify early warning signals and better prevention against the CYN-producing cyanobacteria. In 1992, the strain of Cylindrospermopsis raciborskii from Australia was characterized as potent producer of CYN (Ohtani et al., 1992). So far the CYN-producing C. raciborskii strains have been isolated from Australian and Asian water bodies (Carmichael, 2001; Schembri et al., 2001; Fergusson & Saint, 2003; Mihali et al., 2008; Stüken & Jakobsen, 2010).