Effects of microcin SF608 and microcystin‐LR, two cyanotobacterial compounds produced by Microcystis sp., on aquatic organisms

Abstract

Effects of two cyanobacterial compounds, microcin SF608 and microcystin-LR, were investigated on different physiological parameters of two organisms, the water moss, Vesicularia dubyana, and the waterflea, Daphnia magna. Both compounds are produced by Microcystis species. Microcystin-LR is a potent inhibitor of protein phosphatases 1 and 2A, and microcin SF608 inhibits serine proteases. Other effects of microcystin-LR are well documented in the literature, but adverse effects of microcin SF608 have not been investigated as yet. This study compared the effects of both compounds on detoxication enzymes, microsomal and soluble glutathione-S-transferase (m-, sGST); oxygen stress enzymes, glutathione peroxidase (GP-X), and peroxidase (POD); photosynthetic oxygen production and chlorophyll a:chlorophyll b ratio. mGST was inhibited by both compounds in both organisms, significantly by microcin SF608, possibly indirectly by inhibition of that serine protease transforming the mGST to its active form. The sGST of D. magna was inhibited by microcin SF608, but elevated by microcystin-LR, and elevated by both compounds in V. dubyana. The GP-X in D. magna was not altered by microcin SF608, but elevated parallel to the sGST, whereas the POD in V. dubyana was decreased by both. Photosynthetic oxygen production as well as the chlorophyll a/b ratio showed typical stress reactions, a decrease of oxygen production, and an increase of chlorophyll b, caused both by microcin SF608 and by microcystin-LR. Microcin SF608 was not likely to be detoxified via conjugation to glutathione. The effects of microcin SF608 and microcystin-LR demonstrate that the impact of cyanobacteria on other organisms may not only be directly related to the presently known toxins.

Transgenerational effects of microcystin-LR onDaphnia magna

“…The strongest response to exposure of the parental generation was observed for the sGST, which is the most important enzyme considering its participation in the biotransformation of MC-LR and thus potential involvement in tolerance. In the groups of F1 D. magna that originated from non-exposed mothers, sGST increased in direct relation to MC-LR concentration, confirming previous results and suggesting induction of the enzyme activity as a result of the presence of the toxin and its subsequent biotransformation (Wiegand et al, 2002; OrtizRodríguez and Wiegand, 2010). From studies in vertebrates is known that a structurally diverse range of electronegative, slightly lipophilic xenobiotics triggers induction of GST.…”

“…Control organisms were exposed to methanol at the same concentrations of the exposed groups to ensure that the carrier did not affect the variables measured. These sub-lethal concentrations were chosen because they have been shown to exert a measurable effect on physiological processes in D. magna in acute and chronic toxicity tests (Wiegand et al, 2002;Dao et al, 2010;OrtizRodríguez and Wiegand, 2010). The MC-LR concentration was determined in the exposure media according to Dahlmann et al (Dahlmann et al, 2003) using an HPLC Agilent 1200 Series (Agilent Technologies, Santa Clara, CA, USA) and the MS/MS System 3200 QTrap (AB Sciex, Framingham, MA, USA).…”

“…Up to certain MC-LR concentrations, Daphnia have been shown to respond with increasing enzyme activity of sGST (Wiegand et al, 2002;OrtizRodríguez and Wiegand, 2010). Furthermore, antioxidant enzymes such as catalase (CAT) have been shown to diminish oxidative stress in Daphnia within a certain concentration range of the toxin (Wiegand et al, 2002;Ortiz-Rodríguez and Wiegand, 2010).…”

Influences of Cyanobacterial Toxins Microcystins on the Seedling of Plants

“…These authors also recorded the activity alteration of the enzyme glutathione S-transferase in the macrophytes after toxin exposures. The activities of antioxidant and biotransformation enzymes (superoxide dismutase, peroxidase, catalase, glutathione S-transferase, glutathione peroxidase) from plants were also significantly changed by cyanobacterial crude extracts containing MC, pure MC-LR or anatoxina at the concentration from 0.5 -10 µg·L −1 [10,12,14]. MC-LR induced oxidative stress responses in Lepidium sativum seedlings including lipid peroxidation, change of tocopherol concentrations and profile, and elevation of glutathione enzyme activities [15].…”

“…Pietsch et al [13] and Wiegand et al [14] showed that the photosynthesis of macrophytes, Vesicularia dubyana and Ceratophyllum demersum, was inhibited by cyanobacterial crude extracts or purified cyanotoxins, MC, microcin SF608 and anatoxin-a. These authors also recorded the activity alteration of the enzyme glutathione S-transferase in the macrophytes after toxin exposures.…”