Application of stimulating agents on the immobilized bioluminescence strain Pseudomonas putida mt-2 KG1206,preserved by deep-freezing,for the convenient biomonitoring

This study was conducted to develop methods for the application of an immobilized bioluminescence strain （KG1206）, preserved by deep-freezing （DF）, for the monitoring of contaminated environments. The immobilized cells, preserved by DF, required approximately 2 hr for reconstitution of their activity. A large reduction in bioluminescence was observed due to the DF process; 0.07-0.58 times that of the non deep-frozen （NDF） immobilized strain. The decreased bioluminescence activity induced by the DF process was enhanced by the stimulants, sodium lactate （SL） and KNO3. However, regardless of the inducer chemical tested, the immobilized strain modified with KNO3 consistently produced greater bioluminescence than that treated with SL, in the range of 3.0-10.7 （avg. 6.7± 3.69） and 1.2-4.2 （avg. 2.4 ± 1.47） times that of control, respectively. All KNO3 treatments of contaminated groundwater samples also resulted in an increase in bioluminescence activity, but the rate of stimulation varied for each sample. Also, no strong linear correlation was observed between the bioluminescence and the total concentration of an inducer, which may related to the complex characteristics of the environmental samples. Overall, the results demonstrated the ability of immobilized genetically engineered bacteria, preserved by DF, to measure a specific group of environmental contaminants using a stimulating agent （KNO3）, suggesting the potential for its preliminary application in a field-ready bioassay.

Joint effects of heavy metal binary mixtures on seed germination,root and shoot growth,bacterial bioluminescence,and gene mutation

This investigation was to assess the joint effects of metal binary mixtures on seed germination,root and shoot growth,bacterial bioluminescence,and gene mutation based on the one toxic unit（1 TU）approach.Different sensitivities and orders of toxicity of metal mixtures were observed among the bioassays.In general,mostly additive or antagonistic effects were observed,while almost no synergistic effects by the binary metal mixtures in all bioassays.Therefore,the combined effects of heavy metals in the different bioassays were difficult to generalize since they were dependent on both chemical type and the organism used in each bioassay.However, these results indicate that a battery of bioassays with mixture chemicals as opposed to just a single assay with single metal is a better strategy for the bioassessment of environmental pollutants.

Ecotoxicity evaluation of Cu-and Fe-CNT complexes based on the activity of bacterial bioluminescence and seed germination

The toxic effects of the composites of Fe^0 and Cu^0 with different percentages of CNTs were examined based on the activity of bacterial bioluminescence and seed germination. In terms of the EC50 values, the toxic effects of Cu^0 on bacterial bioluminescence and seed germination were approximately 2 and 180 times greater than that of Fe^0, respectively. The toxicity increased with increasing CNT content in the Cu-CNT mixtures for both organisms,whereas opposite results were observed with Fe-CNT mixtures. The mean toxic effects of Cu-CNT（6%） were approximately 1.3–1.4 times greater than that of Cu-CNT（0%）, whereas the toxic effects of Fe-CNT（6%） were approximately 2.1–2.5 times lower than that of Fe-CNT（0%） for both the bioluminescence activity and seed germination. The causes of this phenomenon are unclear at this point. More research will be needed to elucidate the mechanism of the toxicity of nano-mixture materials and the causes of the different patterns of toxicity with Cu-and Fe-CNT mixtures.