A cost/effective screening method for assessing the toxicity of nutrient rich effluents to algae.

Screening whole effluent toxicity tests are cost/effective methods for detecting the presence of toxic concentrations of unknown pollutants, but the application must solve the problem associated with the effect of high and variable concentrations of nutrients in the effluent on the results of algal toxicity tests. This work proposes a cost/effective test, based on three dilution levels measured at a single point time and a discriminant model for establishing if this kind of complex samples, with difficult interpretation of dilution-response curves, should be considered toxic to algae. This procedure identified properly around 85% of the samples considered toxic by expert judgement.

Cytotoxin production in phytopathogenic and entomopathogenic Serratia marcescens.

In this work, culture filtrates of entomopathogenic and phytopathogenic Serratia marcescens strains induced cytotoxic effects on CHO, Vero and HEp-2 cell lines. Morphological changes on sensitive cells were characterized by cell rounding and detachment as soon as 30 min of incubation, culminating in cell death after 24 h. The cytotoxic effect was completely neutralized by specific antiserum indicating that occur antigenic similarity among cytotoxins produced by these strains. The toxicity assays on plants showed that the culture supernatants did not provoke any visible morphological change and did not affect their growth. By contrast, the plants treated with bacterial suspension showed disease symptom, such as shriveling and decay of stores bulbus in onion and lettuce plantlets. In conclusion, this study show that phytopathogenic and entomopathogenic S. marcescens may produce a cytototoxin similar to that produced by clinical isolates and it is toxic to different mammalian cell lines. These results are especially important for studies involving this bacterium as biological control agent.