Claudia Wiegand

Effects of enteric bacterial and cyanobacterial lipopolysaccharides, and of microcystin-LR, on glutathione S-transferase activities in zebra fish (Danio rerio).

Cyanobacteria (blue-green algae) can produce a variety of toxins including hepatotoxins e.g. microcystins, and endotoxins such as lipopolysaccharides (LPS). The combined effects of such toxins on fish are little known. This study examines the activities of microsomal (m) and soluble (s) glutathione S-transferases (GST) from embryos of the zebra fish, Danio rerio at the prim six embryo stage, which had been exposed since fertilisation to LPS from different sources. A further aim was to see how activity was affected by co-exposure to LPS and microcystin-LR (MC-LR). LPS were obtained from Salmonella typhimurium, Escherichia coli, a laboratory culture of Microcystis CYA 43 and natural cyanobacterial blooms of Microcystis and Gloeotrichia. Following in vivo exposure of embryos to each of the LPS preparations, mGST activity was significantly reduced (from 0.50 to between 0.06 and 0.32 nanokatals per milligram (nkat mg(-1)) protein). sGST activity in vivo was significantly reduced (from 1.05 to between 0.19 and 0.22 nkat mg(-1) protein) after exposure of embryos to each of the cyanobacterial LPS preparations, but not in response to S. typhimurium or E. coli LPS. Activities of both m- and sGSTs were reduced after co-exposure to MC-LR and cyanobacterial LPS, but only mGST activity was reduced in the S. typhimurium and E. coli LPS-treated embryos. In vitro preparations of GST from adult and prim six embryo D. rerio showed no significant changes in enzyme activity in response to the LPS preparations with the exception of Gloeotrichia bloom LPS, where mGST was reduced in adult and embryo preparations. The present study represents the first investigations into the effects of cyanobacterial LPS on the phase-II microcystin detoxication mechanism. LPS preparations, whether from axenic cyanobacteria or cyanobacterial blooms, are potentially capable of significantly reducing activity of both the s- and mGSTs, so reducing the capacity of D. rerio to detoxicate microcystins. The results presented here have wide ranging implications for both animal and human health.

Impact of natural organic matter (NOM) on freshwater amphipods

Natural organic matter (NOM) isolated from the eutrophic Sanctuary Pond (Point Pelee National Park, Canada) has an adverse impact on amphipod species (Gammarus tigrinus and Chaetogammarus ischnus from Lake Müggelsee, Germany, and Eulimnogammarus cyaneus, from Lake Baikal, Russia). Increases in amphipod mortality, changes in peroxidase activity and increases of heat shock protein (hsp70) expression were observed upon exposure to NOM. The highest resistance to the adverse impact of NOM was observed with the endemic Baikalian amphipod E. cyaneus. However, the mechanisms behind this finding remains obscure. If differences in the sensitivity of the hsp70 antibody may be excluded, different modes of action may be postulated: because the adverse impact of NOM may be caused by reactive oxygen species (ROS) and the NOM itself, the observed differences may be due to the action of ROS alone (with E. cyaneus) and a combination of both adverse modes of action (European species).

Analysis of the cyanotoxins anatoxin-a and microcystins in Lesser Flamingo feathers

Feathers from carcasses of the Lesser Flamingo (Phoeniconaias minor), which had died after ingesting cyanobacterial toxins (cyanotoxins) contained between 0.02 and 30.0u2009µg microcystin-LR equivalents per gram of feather according to HPLC and ELISA analysis of feather extracts. Anatoxin-a was detected less frequently in the Lesser Flamingo feathers, up to 0.8u2009µg anatoxin-a per gram of feather being recorded. When feathers from different body regions were analysed and compared for microcystins and anatoxin-a, wing feathers were found to contain the highest concentrations of these cyanotoxins, the order of concentration and frequency of analytical detection being wingu2009>u2009breastu2009>u2009head. Consistent with the presence of the microcystins and anatoxin-a in gut contents and the livers of the dead birds and negligible in vitro adsorption to feathers, the cyanotoxins associated with the feathers of the dead wild flamingos are inferred to be primarily of dietary origin. †Dedicated to the memory of Ekkehard and Angelika Vareschi.

Contribution of tixic cynobacteria to massive deaths of lesser flamingoes at saline-alkaline lakes of Kenya

The saline-alkaline lakes of the African Rift Valley are home to a large population o f the Lesser Flamingo (Phoeniconaias minor GEOFFREY). With 1-3 mii. lion individuals, these lakes are established as one of the most fascinating bird spectacles of the world (BROWN 1959). The population density o f the flamingos at the different lakes is subject to wide fluctuations depending on changes in food quantity, breeding activity and episodic mass deaths (OWINO et al. 200 l; Fig. l). The main causes o f the high flamingo mortalities are thought to be infections by mycobacteria (SILEO et al. 1979, KocK et al. 1999), poisoning