Uranium (U)-Tolerant Bacterial Diversity from U Ore Deposit of Domiasiat in North-East India and Its Prospective Utilisation in Bioremediation

Abstract

Uranium (U)-tolerant aerobic chemo-heterotrophic bacteria were isolated from the sub-surface soils of U-rich deposits in Domiasiat, North East India. The bacterial community explored at molecular level by amplified ribosomal DNA restriction analysis (ARDRA) resulted in 51 distinct phylotypes. Bacterial community assemblages at the U mining site with the concentration of U ranging from 20 to 100 ppm, were found to be most diverse. Representative bacteria analysed by 16S rRNA gene sequencing were affiliated to Firmicutes (51%), Gammaproteobacteria (26%), Actinobacteria (11%), Bacteroidetes (10%) and Betaproteobacteria (2%). Representative strains removed more than 90% and 53% of U from 100 μM and 2 mM uranyl nitrate solutions, respectively, at pH 3.5 within 10 min of exposure and the activity was retained until 24 h. Overall, 76% of characterized isolates possessed phosphatase enzyme and 53% had PIB-type ATPase genes. This study generated baseline information on the diverse indigenous U-tolerant bacteria which could serve as an indicator to estimate the environmental impact expected to be caused by mining in the future. Also, these natural isolates efficient in uranium binding and harbouring phosphatase enzyme and metal-transporting genes could possibly play a vital role in the bioremediation of metal-/radionuclide-contaminated environments.

Effects of long-term radionuclide and heavy metal contamination on the activity of microbial communities, inhabiting uranium mining impacted soils

“…The significance of metal phosphorylation as a survival strategy for microorganisms is confirmed by our results of increased Ac/AlPA synthesis in more contaminated soils. Our results are in line with Kumar et al (2013) who showed that 76 % of the culturable bacteria isolated from U deposits possessed constitutive phosphatase activity, and Yung and Yiao (2014), who reported that AlPA is an enzyme which was neither induced nor inhibited by U contamination. Among the most common AlPA producers are members of Gammaproteobacteria, Actinobacteria, and Bacteroidetes (Kumar et al 2013), and all of these taxa along Acidobacteria were found in Bulgarian U polluted Buhovo and Sliven (Radeva et al 2013), and Senokos (unpublished data) mining sites with increasing share in the bacterial communities along the U and HM gradient of contamination.…”

“…Our results are in line with Kumar et al (2013) who showed that 76 % of the culturable bacteria isolated from U deposits possessed constitutive phosphatase activity, and Yung and Yiao (2014), who reported that AlPA is an enzyme which was neither induced nor inhibited by U contamination. Among the most common AlPA producers are members of Gammaproteobacteria, Actinobacteria, and Bacteroidetes (Kumar et al 2013), and all of these taxa along Acidobacteria were found in Bulgarian U polluted Buhovo and Sliven (Radeva et al 2013), and Senokos (unpublished data) mining sites with increasing share in the bacterial communities along the U and HM gradient of contamination. Additionally, multi-metal (Cd, Co, Cr, Zn, and Ni (except DhA)) tolerance of AlPA and DhA is found than AcPA (Pb), determining the activities of AlPA and DhA as crucial for site cycling of OM and detoxification of metals, even in slightly acidic soils.…”

Combined use of flow cytometry and microscopy to study the interactions between the gram-negative betaproteobacterium Acidovorax facilis and uranium(VI)

“…Compared to indigenous microorganisms, the uranium tolerance of A. facilis was relatively moderate. Natural isolates from ore deposit in northeast India have displayed tolerances up to 4.0 mM [44].…”

Uranium Bioremediation: Approaches and Challenges

“…The concentrations of uranium that inhibited growth of various organisms like Deinococcus radiodurans, Escherichia coli, Pseudomonas putida, Caulobacter crescentus and Shewanella putrefaciens ranged from 500 μM to 3 mM (Hu et al 2005;Ruggiero et al 2005;Wade and DiChristina 2000). The minimum inhibitory concentration (MIC) for bacterial (aerobic, chemoheterotrophic) isolates from subsurface soils of uranium-rich deposits was found to be 4 mM (Kumar et al 2013a). The chemical toxicity studies for uranium have reported inhibition of growth of aquatic microflora including algae, cyanobacteria and other aquatic microorganisms at 4.2 μM in freshwater systems, whereas the bactericidal activity of this radionuclide is reported at a concentration of~420 μM (Driver 1994).…”

“…The gamma radiation dose was found to bẽ 11 μGy/h at a sampling site of uranium-rich deposit harbouring 5 mM of uranium (~1,200 ppm) (Acharya et al unpublished result). The strains isolated from such site showed high tolerance not only to uranium (4 mM) but also to various other heavy metals like copper, cadmium and lead (Kumar et al 2013a). …”