Isolation and Identification of Uranium Tolerant Phosphate-Solubilizing Bacillus spp. and Their Synergistic Strategies to U(VI) Immobilization

Abstract

The remediation of uranium (U) through phosphate-solubilizing bacteria (PSB) is an emerging technique as well as an interesting phenomenon for transforming mobile U into stable minerals in the environment. While studies are well needed for in-depth understanding of the mechanism of U(VI) immobilization by PSB. In this study, two PSB were isolated from a U-tailing repository site. These bacterial strains (ZJ-1 and ZJ-3) were identified as Bacillus spp. by the sequence analysis of 16S ribosomal RNA (rRNA) genes. Incubation of PSB in liquid medium showed that the isolate ZJ-3 could solubilize more than 230 mg L–1 P from glycerol-3-phosphate and simultaneously removed over 70% of 50 mg L–1 U(VI) within 1 h. During this process, the rapid appearance of yellow precipitates was observed. The microscopic and spectroscopic analysis demonstrated that the precipitates were associated with U-phosphate compound in the form of saleeite-like substances. Besides, scanning electron microscopy coupled with energy-dispersive X-ray (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR) analysis of the precipitates confirmed that the extracellular polymeric substances (EPS) might also play a key role in U sequestration. Furthermore, SEM and FTIR analysis revealed that part of U(VI) was adsorbed on the bacterial surface through cellular phosphate, hydroxy, carboxyl, and amide groups. This study provides new insights into the synergistic strategies enhancing U immobilization rates by Bacillus spp. that uses glycerol-3-phosphate as the phosphorus source, the process of which contributes to harmful pollutant biodegradation.

Response and Dynamic Change of Microbial Community during Bioremediation of Uranium Tailings by Bacillus sp.

“…The pH decreased with time; Bacillus sp. decreased the pH of the system, as we found in our previous research [18]. However, pH was stabilized during days 7-28.…”

“…This strain identified as Bacillus sp. (preserved in Wuhan University M2019958) was initially isolated and purified from the uranium tailings pile in southern of China, and preserved in National Engineering Laboratory of Biohydrometallurgy, GRINM Group Corporation Limited [18].…”

Plant Growth-Promoting Activity of Bacillus sp. PG-8 Isolated From Fermented Panchagavya and Its Effect on the Growth of Arachis hypogea

“…Rhizospheric isolate Bacillus cereus was able to solubilize 140 µg/ml phosphate after 3 days (Abdelmoteleb and Gonzalez-Mendoza, 2020). Bacillus xijun isolated from rhizospheric soil solubilized 130 µg/ml phosphate after 15 days showing pH drop from 7.0 to 4.7 (Zhong et al, 2021). The Bacillus sp.…”

Optimization of Environmental Conditions for Microbial Stabilization of Uranium Tailings, and the Microbial Community Response

“…At present, research on the control treatment of uranium pollution has developed from efficient removal to stabilization, but it is mostly focused on the treatment of uranium pollution in water and soil ( Kim et al, 2013 ; Khan, 2020 ; Zhong et al, 2021 ), and there are few reports about the stabilization of tailings. Many studies have shown that pH, temperature, inoculation volume, and other environmental factors can change the functional expression of microorganisms by affecting their growth and metabolism ( Ji and Wei, 2006 ; Senko et al, 2007 ; Zhao, 2014 ).…”

“…However, bioremediation is exactly suitable for uranium-contaminated sites with large polluted area and low pollution degree and has received great attention in recent years (Jing et al, 2020), wherein microbial remediation technology has the outstanding advantages of low cost, easy operation, and small disturbance to the environment, providing a greener, economic, and stable way for the remediation of uraniumcontaminated sites and is considered to have great research value and broad application prospects (Lakaniemi et al, 2019). In the field of uranium pollution control, many studies have shown that sulfate-reducing bacteria (Hu et al, 2011;He et al, 2021) and phosphate-solubilizing bacteria (Zhong et al, 2021) can significantly alleviate the toxicity of uranium in the environment through bio-reduction (Zhong et al, 2019), bio-precipitation (Yao, 2017), bio-adsorption (Yong and Macaskie, 2010), and other approaches. However, there is limited information on the combined effect of the two functional strains.…”