Differential radio-tolerance of nutrition-induced morphotypes of Deinococcus radiodurans R1.

Deinococcus radiodurans R1 is a highly radio-tolerant bacterium. Depending on the nutrient availability D. radiodurans R1 exists in three morphologies viz. monococcal, diplococcal and tetracoccal. In this study, we examined whether nutrition-induced morphotypes of D. radiodurans showed similar DNA damage upon gamma radiation exposure. Total DNA damage after radiation exposure was estimated by comparing percent double-strand breaks (DSBs) in genomic DNA. It was found that all three morphotypes exhibited different radiation tolerances which were also dependent on the radiation dose given. Monococcal forms were found to be most radio-tolerant at most of the tested radiation doses. Results showed that these nutrient-starved-condition induced morphotypes show lesser DNA DSBs upon irradiation, hence show higher radio-tolerance.

Removal of toxic Co-EDTA complex by a halophilic solar-salt-pan isolate Pseudomonas aeruginosa SPB-1.

In this study, a promising bioremediation approach was developed to remove [Co(III)-EDTA](-) complex that is generated during the waste management process. Though several studies have been reported on bioremediation of cobalt, the removal of [Co(III)-EDTA](-) complex has not been tested. A [Co(III)-EDTA](-) resistant bacterium, Pseudomonas aeruginosa SPB-1 was isolated from the solar-salt-pan and physical parameters were optimized for its growth. The various studies showed that the removal of [Co(III)-EDTA](-) from the bulk liquid was due to the adsorption of the complex by the biomass. Using absorption/desorption isotherm over a range of pH (1-8), the maximum adsorption of [Co(III)-EDTA](-) was found to be at pH 7.0 and maximum desorption from the biomass occurred at pH 1.0, thus rendering an ion exchange property to P. aeruginosa SPB-1 biomass. P. aeruginosa SPB-1 biomass could be used as bio-resin that showed 80.4±3.27% adsorption capacity up to fourth cycle and the biomass was viable till the ninth cycle with 10.5±7.3% adsorption. Radiation tolerance potential i.e. D10 value for the strain was found to be ~300 Gy, which suggests the potential use of the bacterium in bioremediation of moderately active nuclear waste.