Effect of bacteria on pre-formed and nascent biofilms of Irpex lacteus

Fungal biofilms are applicable to removal of pollutants in biofilters in nonsterile conditions but the bacterial effect is poorly known. Interactions between fungal and bacterial organisms were investigated in preformed or nascent biofilms and the enzyme activities and degradation capacity measured. Different effects of Escherichia coli and Pseudomonas aeruginosa on degradation of an anthraquinone dye by fungal biofilms colonizing polyurethane foam (PUF) in the presence of bacteria (104-106 CFU) at pH 4.5 and 6 were observed in a 10-day experiment: the former bacterium inhibited degradation whereas the latter not. Production of peroxidases but not of laccase was reduced; the bacteria could not remove the dye. The fungal biomass amount colonizing PUF was unaffected by bacteria, E. coli and P. aeruginosa increased their respective counts by 1 to 3 and 0 to 2 orders of magnitude. In contrast, the degradation capacity (85-95% decolorization rate at pH 5.5) of preformed 1-week-old fungal biofilms colonizing PUF or pinewood was not affected by the added 106 CFU of E.coli in a 4-week experiment. The fungal growth was reduced 1.4-fold and bacterial counts increased up to 2-fold compared to bacterial controls. The results demonstrate a significant resistance of preformed I. lacteus biofilms to bacterial stress which is important for practical application.The work was supported by the project IAAX00200901

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

Use of protista and algae to study toxicity of dye compounds

Comparative assessment of the toxicological effects of two azo dyes [Reactive Orange 16 (R016); Congo Red (CR)] and two anthraquinone dyes [Remazol Brilliant Blue R (RBBR); Disperse Blue 3 (DB3)] was performed on two in vitro cell models, the ciliate protozoa Tetrahymena pyriformis and the microalga Selenastrum capricornutum. Growth impairment, viability assay using calcein AM and ethidium homodimer-1 (CAM/EthD-1 assay), grazing and morphometric assay were the tests performed on T pyriformis using 48 h-tests. They represented simple and fast bioassays providing overall information on the morphological and physiological state of the cells exposed to different dyes. The algal test measured growth inhibition after a 96-h exposure. The anthraquinone dye DB3 was found to be the most toxic dye among all the dyes tested. The EC50 value of 0.5 ± 0.0 mg/l detected in the algal test was 10 to 100-fold lower compared to other dyes tested