Comparative use of bacterial, algal and protozoan tests to study toxicity of azo-and anthraquinone dyes

Toxicity of two azo dyes (Reactive Orange 16 (RO16); Congo Red (CR)) and two anthraquinone dyes (Remazol Brilliant Blue R (RBBR); Disperse Blue 3 (DB3)) were compared using bacterium Vibrio fischeri, microalga Selenastrum capricornutum and ciliate Tetrahymena pyriformis. The following respective endpoints were involved: acute toxicity measured as bacterial luminescence inhibition, algal growth inhibition, and the effects on the protozoa including viability, growth inhibition, grazing effect and morphometric effects. In addition, mutagenicity of the dyes was determined using Ames test with bacterium Salmonella typhimurium Hisˉ. DB3 dye was the most toxic of all dyes in the bacterial, algal and protozoan tests. In contrast to other dyes, DB3 exhibited mutagenic effects after metabolic activation in vitro in all S. typhimurium strains used. Of the methods applied, the algal test was the most sensitive to evaluate toxicity of the dyes tested.GRICES, Portugal/ASCR, Czech Republic (Bilateral Cooperative Project), Grant Agency of the Czech Republic, Ministry of Education, Youth and Sports of the Czech Republic and Institutional Research. Centro de Engenharia Biológica, Universidade do Minho, Braga. IFA Tulln.Charles University

Microbial co-occurrence patterns in deep Precambrian bedrock fracture fluids

The bacterial and archaeal community composition and the possible carbon assimilation processes and energy sources of microbial communities in oligotrophic, deep, crystalline bedrock fractures is yet to be resolved. In this study, intrinsic microbial communities from groundwater of six fracture zones from 180 to 2300aEuro-m depths in Outokumpu bedrock were characterized using high-throughput amplicon sequencing and metagenomic prediction. Comamonadaceae-, Anaerobrancaceae- and Pseudomonadaceae-related operational taxonomic units (OTUs) form the core community in deep crystalline bedrock fractures in Outokumpu. Archaeal communities were mainly composed of Methanobacteriaceae-affiliating OTUs. The predicted bacterial metagenomes showed that pathways involved in fatty acid and amino sugar metabolism were common. In addition, relative abundance of genes coding the enzymes of autotrophic carbon fixation pathways in predicted metagenomes was low. This indicates that heterotrophic carbon assimilation is more important for microbial communities of the fracture zones. Network analysis based on co-occurrence of OTUs revealed possible "keystone" genera of the microbial communities belonging to Burkholderiales and Clostridiales. Bacterial communities in fractures resemble those found in oligotrophic, hydrogen-enriched environments. Serpentinization reactions of ophiolitic rocks in Outokumpu assemblage may provide a source of energy and organic carbon compounds for the microbial communities in the fractures. Sulfate reducers and methanogens form a minority of the total microbial communities, but OTUs forming these minor groups are similar to those found in other deep Precambrian terrestrial bedrock environments.Peer reviewe

Detection of toxicity released by a biodegradable plastic after composting in activated vermiculite

The composting test method based on activated vermiculite is a comprehensive system for the assessment of the environmental impact of biodegradable plastics. It allows, in a single test, (i) the measurement of the mineralization of the polymer under study; (ii) the retrieval of the final polymeric residues and (iii) determination of the biomass (to make a final mass balance); (iv) detection of breakdown products of the original polymer. In this study it is shown that the vermiculite test method is also suitable to perform ecotoxicological studies. The Flash test is a method based on kinetic measurement of bioluminescence by Vibrio fischeri, and was applied to evaluate the toxicity of compost samples and vermiculite samples after the biodegradation of a polyurethane (PU) based plastic material. Toxicity was detected in vermiculite samples contaminated by 4,4′ diamino diphenyl methane (MDA), a toxic breakdown product released by the PU moiety, as shown by HPLC. On the other hand, neither toxicity nor the presence of MDA was detected in mature compost. A recovery experiment previously performed had shown a 10% MDA recovery yield from mature compost. The possibility of testing the ecotoxicity of extracts obtained from mineral matrix after biodegradation makes the vermiculite test system particularly interesting for the overall assessment of the environmental impact of biodegradable plastics