Molecular level insight of thiocyanate degradation by Pseudomonas putida TDB-1 under a high arsenic and alkaline condition.

It is a big challenge to bioremediate thiocyanate pollution in the gold extraction heap leaching tailings and surrounding soils with high contents of arsenic and alkali. Here, a novel thiocyanate-degrading bacterium Pseudomonas putida TDB-1 was successfully applied to completely degrade 1000 mg/L thiocyanate under a high arsenic (400 mg/L) and alkaline condition (pH = 10). It also leached the contents of thiocyanate from 1302.16 to 269.72 mg/kg in the gold extraction heap leaching tailings after 50 h. The maximum transformation rates of S and N in thiocyanate to the two finial products of SO42- and NO3- were 88.98 % and 92.71 %, respectively. Moreover, the genome sequencing confirmed that the biomarker gene of thiocyanate-degrading bacterium, CynS was identified in the strain TDB-1. The bacterial transcriptome revealed that critical genes, such as CynS, CcoNOQP, SoxY, tst, gltBD, arsRBCH and NhaC, etc. in the thiocyanate degradation, S and N metabolisms, and As and alkali resistance were significantly up-regulated in the groups with 300 mg/L SCN- (T300) and with 300 mg/L SCN- and 200 mg/L As (TA300). In addition, the protein-protein interaction network showed that the glutamate synthase encoding by gltB and gltD served as central node to integrate the S and N metabolism pathways with thiocyanate as substrate. The results of our study provide a novel molecular level insight for the dynamic gene expression regulation of thiocyanate degradation by the strain TDB-1 with a severe arsenic and alkaline stress.

Simultaneous immobilization of Pb, Cd and As in soil by hybrid iron-, sulfate- and phosphate-based bio-nanocomposite: Effectiveness, long-term stability and bioavailablity/bioaccessibility evaluation.

Here, the bio-nanocomposite (n-HFP + n-HFS)@An was developed to simultaneously immobilize Pb, Cd and As in the severely contaminated soil. The immobilization rates of diethylenetriaminepentaacetic acid (DTPA)/decarbonate-extracted bioavailable Pb, Cd and As were 59.87%, 31.28% and 62.30%, and the immobilization rates of their water-soluble forms were 63.12%, 60.02% and 89.39%, respectively. Moreover, the ten-year acid rain simulated leaching assay showed that the maximum cumulative release contents of Pb, Cd and As in the treated soil samples were decreased by 2.94, 2.46 and 40.60 times, comparing to the un-treated ones. Additionally, the results of SBRC (Solubility Bioaccessibility Research Consortium) revealed that the bioaccessible rates of the three metals in intestinal phase were lower than in gastric phase, and both of them decreased with increasing the immobilization time. The gastric bioaccessibility of Pb, Cd and As had a higher correlation with the contents of water-soluble forms, while the intestinal bioaccessibility was more strongly positively associated with the bioavailable forms.

Dynamic proteome responses to sequential reduction of Cr(VI) and adsorption of Pb(II) by Pannonibacter phragmitetus BB.

Here, the microbial responses to Cr(VI) and Pb(II) with bio-removal of the metals in water by Pannonibacter phragmitetus BB were explored. The comparative bacterial proteomics showed that the intracellular and extracellular Cr(VI) reduction proteins, Pb(II) adsorption by the lipoprotein and sugar-related bacterial proteins, as well as Pb(II) precipitation by phosphate and OH- were vital to the bio-removal of Cr(VI) and Pb(II). Moreover, the influx and efflux channels of Cr(VI) and Cr(III), Pb(II) transporters, extracellular siderophores for Pb(II) complexation and antioxidant proteins enabled the strain BB to resist the toxicity of Cr(VI) and Pb(II). In addition, the dynamic expression levels of the proteins related to reduction and transportation of Cr(VI), and adsorption, transportation and complexation of Pb(II) were dependent on the corresponding metal, respectively. The anti-oxidative stress system, such as superoxide dismutase, and Na+/H+ antiporters played central roles in the protein-protein interaction network to resist and detoxify Cr(VI) and Pb(II). The results of our study provide a novel insight for the physiological responses of the strain BB to the combined stresses of Pb(II) and Cr(VI).

Simultaneous adsorption of As(III), Cd(II) and Pb(II) by hybrid bio-nanocomposites of nano hydroxy ferric phosphate and hydroxy ferric sulfate particles coating on Aspergillus niger.

To develop an efficient, convenient and cost-effective method to simultaneously remove pollution of As(III), Cd(II) and Pb(II) in wastewater, a strategy to fabricate hybrid bio-nanocomposites ((n-HFP + n-HFS)@An) of nano hydroxy ferric phosphate (n-HFP) and hydroxy ferric sulfate (n-HFS) particles coating on Aspergillus niger was applied. The scanning electron microscope and energy dispersive spectrum analyses showed that (n-HFP + n-HFS)@An composites had been successfully developed which well solved the self-agglomeration problem of the nano particles. Comparing to the bulk nanoparticles, the adsorption rates of the (n-HFP + n-HFS)@An composites for the three metals were promoted 145.34, 28.98 and 25.18% and reached 76.84, 73.62 and 94.31%, respectively. Similarly, the adsorption capacities for As(III), Cd(II), and Pb(II) were 162.00, 205.83 and 730.79 mg/g, respectively. Moreover, the pseudo-second-order kinetic model was more relevant to the adsorption on the three metals by (n-HFP + n-HFS)@An, and adsorbing As(III) was fitted to the Freundlich isotherm model, while the adsorption on Cd(II) or Pb(II) was related to the Langmuir isotherm model. In addition, the adsorption of Cd(II) and Pb(II) was associated with transformation of hydroxyl groups and precipitation with phosphate. As(III) was adsorbed through exchange between AsO2- and SO42- in the (n-HFP + n-HFS)@An composites.