Genotoxicity of crude extracts of cyanobacteria from Taihu Lake on carp (Cyprinus carpio)

Management of toxic cyanobacteria for drinking water production of Ain Zada Dam

Blooms of toxic cyanobacteria in Algerian reservoirs represent a potential health problem, mainly from drinking water that supplies the local population of Ain Zada (Bordj Bou Arreridj). The objective of this study is to monitor, detect, and identify the existence of cyanobacteria and microcystins during blooming times. Samples were taken in 2013 from eight stations. The results show that three potentially toxic cyanobacterial genera with the species Planktothrix agardhii were dominant. Cyanobacterial biomass, phycocyanin (PC) concentrations, and microcystin (MC) concentrations were high in the surface layer and at 14 m depth; these values were also high in the treated water. On 11 May 2013, MC concentrations were 6.3 μg/L in MC-LR equivalent in the drinking water. This study shows for the first time the presence of cyanotoxins in raw and treated waters, highlighting that regular monitoring of cyanobacteria and cyanotoxins must be undertaken to avoid potential health problems.

Impact of the toxicity of Cylindrospermopsis raciborskii (Woloszynska) Seenayya & Subba Raju on laboratory rats in vivo

In vivo laboratory studies of toxicity were performed on Wistar rats using a methanol extract produced by the natural population of Cylindrospermopsis raciborskii (abundance of 2.13 × 10⁵ trichomes mL^-1) collected at Aleksandrovac Lake (Serbia). HPLC analysis showed that the extract contains 6.65 μg cylindrospermopsin (CYN) mg^-1. The rats were killed 24 or 72 h after a single intraperitoneal injection of C. raciborskii extract in concentrations of 1500, 3000, 6000 and 12,000 μg kg^-1 body weight (bw) and an equivalent amount of CYN as present in the highest dose of the extract (79.80 μg CYN kg^-1 bw). The genotoxic effect on the livers treated with C. raciborskii was evaluated using comet assay and potential induction of oxidative stress as the toxicity mechanism associated with the presence of CYN in extract. The results from the analyses of DNA damage in the comet tail length, tail moment and percentage of DNA in the tail in the liver indicated that administration of extract and CYN present statistically significant difference when compared with the negative control group. Although an increase in the frequency of selected parameters induced by the CYN was observed in the liver, this damage was less than the damage resulting from the administration of the highest dose of extract. The changes in the biochemical parameters of the hepatic damage showed that the application of single doses of the extract and CYN did not cause serious liver damage in rats. The extract and CYN significantly increased oxidative stress in rats' liver after a single exposure.

Biodegradation of the aminopolyphosphonate DTPMP by the cyanobacterium Anabaena variabilis proceeds via a C-P lyase-independent pathway

Cyanobacteria, the only prokaryotes capable of oxygenic photosynthesis, play a major role in carbon, nitrogen and phosphorus global cycling. Under conditions of increased P availability and nutrient loading, some cyanobacteria are capable of blooming, rapidly multiplying and possibly altering the ecological structure of the ecosystem. Because of their ability of using non-conventional P sources, these microalgae can be used for bioremediation purposes. Under this perspective, the metabolization of the polyphosphonate diethylenetriaminepenta(methylenephosphonic) acid (DTPMP) by the strain CCALA 007 of Anabaena variabilis was investigated using ³¹ P NMR analysis. Results showed a quantitative breakdown of DTPMP by cell-free extracts from cyanobacterial cells grown in the absence of any phosphonate. The identification of intermediates and products allowed us to propose a unique and new biodegradation pathway in which the formation of (N-acetylaminomethyl)phosphonic acid represents a key step. This hypothesis was strengthened by the results obtained by incubating cell-free extracts with pathway intermediates. When Anabaena cultures were grown in the presence of the phosphonate, or phosphorus-starved before the extraction, significantly higher biodegradation rates were found.

Characterization and expression analysis of Calmodulin (CaM) in orange-spotted grouper (Epinephelus coioides) in response to Vibrio alginolyticus challenge

Vibrio alginolyticus containing the highly toxic extracellular product is one of the most serious threats to grouper survival and its minimum lethal dose is approximately 500 CFU/g fish body weight in grouper. To study the toxic effects of V. alginolyticus on the immune system in teleost, Calmodulin (CaM), an important molecular indicator gene, was cloned from the orange-spotted grouper (Epinephelus coioides). The full-length Ec-CaM consisted of a 5'-UTR of 103 bp, an ORF of 450 bp and a 3'-UTR of 104 bp. The Ec-CaM gene encoded a protein of 149 amino acids with an estimated molecular mass of 16.4 kDa and a predicted isoelectric point of 3.93. The deduced amino acid sequence showed that Ec-CaM contained four highly conserved EF-hand domains known to be critical for the function of CaM. Ec-CaM was widely expressed and the highest expression level was observed in liver. Following V. alginolyticus challenge, a sharp increase level of respiratory burst activity and apoptosis ratio were observed. Further analyses of CaM expression and p53 expression in liver, kidney and spleen by qRT-PCR demonstrated that the up-regulated expression of CaM and p53 were observed in the vibrio challenge group. Western blotting analysis confirmed that the Ec-CaM protein was strongly induced in liver at 12 h post-injection, while a sharp increase of p53 protein expression was observed at 24 h post-injection. These results showed CaM expression serving as a potential molecular indicator may help to assess the toxicological effects of V. alginolyticus on the ROS generation and apoptotic process in grouper.

Effects of Dietary Exposure to Zearalenone (ZEN) on Carp (Cyprinus carpio L.)

The mycotoxin zearalenone (ZEN) is frequently contaminating animal feeds including feed used in aquaculture. In the present study, the effects of dietary exposure to ZEN on carp (Cyprinus carpio L.) were investigated. ZEN at three different concentrations (low dose: 332 µg kg⁻¹, medium dose: 621 µg kg⁻¹ and high dose: 797 µg kg⁻¹ final feed, respectively) was administered to juvenile carp for four weeks. Additional groups received the mycotoxin for the same time period but were fed with the uncontaminated diet for two more weeks to examine the reversibility of the ZEN effects. No effects on growth were observed during the feeding trial, but effects on haematological parameters occurred. In addition, an influence on white blood cell counts was noted whereby granulocytes and monocytes were affected in fish treated with the medium and high dose ZEN diet. In muscle samples, marginal ZEN and α-zearalenol (α-ZEL) concentrations were detected. Furthermore, the genotoxic potential of ZEN was confirmed by analysing formation of micronuclei in erythrocytes. In contrast to previous reports on other fish species, estrogenic effects measured as vitellogenin concentrations in serum samples were not increased by dietary exposure to ZEN. This is probably due to the fact that ZEN is rapidly metabolized in carp.