Study on the performance of carbonate-mineralized bacteria combined with eggshell for immobilizing Pb and Cd in water and soil

Microbially induced carbonate precipitation (MICP) is an advanced bioremediation approach to remediate heavy metal (HM)-contaminated water and soil. In this study, metal-tolerant urease-producing bacterial isolates, namely, UR1, UR16, UR20, and UR21, were selected based on their urease activity. The efficiency of these isolates in water for Pb and Cd immobilizations was explored. Our results revealed that UR21 had the highest removal rates of Pb (81.9%) and Cd (65.0%) in solution within 72 h through MICP. The scanning electron microscopy-energy-dispersive x-ray and x-ray diffraction analysis confirmed the structure and the existence of PbCO₃ and CdCO₃ crystals in the precipitates. In addition, the strain UR21, in combination with urea/eggshell waste (EGS) or both, was further employed to investigate the effect of MICP on soil enzymatic activity, chemical fractions, and bioavailability of Pb and Cd. The outcomes indicated that the applied treatments reduced the proportion of soluble-exchangeable-Pb and -Cd, which resulted in an increment in carbonate-bound Pb and Cd in the soil. The DTPA-extractable Pb and Cd were reduced by 29.2% and 25.2% with the treatment of UR21+urea+EGS as compared to the control. Besides, the application of UR21 and EGS significantly increased the soil pH, cation exchange capacity, and enzyme activities. Our findings may provide a novel perceptive for an eco-friendly and sustainable approach to remediate heavy metal-contaminated environment through a combination of metal-resistant ureolytic bacterial strain and EGS.

Subtractive proteomics to identify targets for vaccine development against vancomycin-resistant Enterococcus faecalis

Aim: Due to the increased level of vancomycin resistance in Enterococci species, an aggressive treatment involving targeted antibiotics is required to manage this frequently occurring infection. Materials & methods: Here, subtractive proteomics and reverse vaccinology approaches were employed to identify potential target and for the prediction of B cell and T cell epitopes against vancomycin-resistant Enterococcus faecalis (VRE V583). Results: The results exhibited the presence of 73 out of 805 non-homologous protein sequences in the proteome which can be employed as unique targets to develop the novel drugs and vaccine to counter the deadly infections caused by this microbe. Conclusion: The identified novel target in VRE V583 will equip our knowledge to design effective vaccine against probable protease EEP proteins.