A test battery approach to the ecotoxicological evaluation of cadmium and copper employing a battery of marine bioassays.

Heavy metals are ubiquitous contaminants of the marine environment and can accumulate and persist in sediments. The toxicity of metal contaminants in sediments to organisms is dependent on the bioavailability of the metals in both the water and sediment phases and the sensitivity of the organism to the metal exposure. This study investigated the effects of two metal contaminants of concern (CdCl(2) and CuCl(2)) on a battery of marine bioassays employed for sediment assessment. Cadmium, a known carcinogen and widespread marine pollutant, was found to be the least toxic of the two assayed metals in all in vivo tests. However, CdCl(2) was found to be more toxic to the fish cell lines PLHC-1 and RTG-2 than CuCl(2). Tisbe battagliai was the most sensitive species to both metals and the Microtox and cell lines were the least sensitive (cadmium was found to be three orders of magnitude less toxic to Vibrio fischeri than to T. battagliai). The sensitivity of Tetraselmis suecica to the two metals varied greatly. Marine microalgae are among the organisms that can tolerate higher levels of cadmium. This hypothesis is demonstrated in this study where it was not possible to derive an EC(50) value for CdCl(2) and the marine prasinophyte, T. suecica. Conversely, CuCl(2) was observed to be highly toxic to the marine alga, EC(50) of 1.19 mg l(-1). The genotoxic effect of Cu on the marine phytoplankton was evaluated using the Comet assay. Copper concentrations ranging from 0.25 to 2.50 mg l(-1) were used to evaluate the effects. DNA damage was measured as percent number of comets and normal cells. There was no significant DNA damage observed at any concentration of CuCl(2) tested and no correlation with growth inhibition and genetic damage was found.

Plastid-derived Type II fatty acid biosynthetic enzymes in chromists.

Fatty acid biosynthesis is a critical process for living organisms, but the evolution of the enzymes involved in this pathway is poorly understood. Animals and fungi use a Type I fatty acid synthase (FAS), a large multifunctional protein found in the cytosol. Bacteria use a Type II complex, where each enzymatic domain is a discrete polypeptide. In plants, fatty acid biosynthesis takes place in the plastid, and utilises a Type II enzyme complex. Recently, the apicomplexan parasites Plasmodium and Toxoplasma have been shown to contain the plastid-targeted Type II FAS. To investigate the distribution of this pathway, we have characterised two Type II enzymes, FabD and FabI, in three other eukaryotes with plastids derived from red algal endosymbionts: cryptomonads, heterokonts, and haptophytes. Collectively, these are referred to as chromists, and are thought to be related to apicomplexa and their relatives. Phylogenies of these enzymes show that the plastid Type II FAS enzymes are found in all groups studied, which most likely means that they originated from the red algal endosymbiont at the outset of the secondary endosymbiosis of their plastids. In addition, although plastid fab D genes are clearly related to one another, they are not related to cyanobacterial homologues, as would be expected. On the other hand, the strongly supported plastid fab I clade is related to cyanobacteria, and contains genes from chlamydiales.