Jiaokun Li

Lead (Pb) contamination poses a serious threat to soil ecosystems, crop productivity, and food safety. The use of Pb-resistant plant growth-promoting bacteria (PGPB) offers a sustainable and eco-friendly strategy for soil bioremediation. In this study, a novel Pb-tolerant PGPB strain, Pseudomonas mendocina L1, was isolated from phosphate rock-contaminated soil. Strain L1 exhibited high Pb resistance (MIC = 1000 mg/L) and multiple plant growth-promoting traits, including phosphate solubilization, indole-3-acetic acid (IAA) and siderophore production, as well as ACC deaminase activity. Whole-genome sequencing (WGS) revealed that strain P. mendocina L1 harbors a 5.54 Mb circular chromosome with a GC content of 62.39% and 5136 predicted coding sequences. Genomic analysis identified key genes involved in plant-beneficial functions, such as phosphate transport (pstA, pstB, pstC, pstS), siderophore-mediated iron uptake (fhuB, fhuC, fhuD), and IAA biosynthesis (trpEDCBA operon, trpF). Furthermore, a soil–pakchoi (Brassica chinensis L.) system was employed to evaluate its bioremediation potential, demonstrating that inoculation with P. mendocina L1 significantly improved plant growth while reducing Pb accumulation in edible tissues. These findings highlight P. mendocina L1 as a promising candidate for the bioremediation of Pb-contaminated soils, offering an eco-friendly and cost-effective strategy for sustainable agriculture and environmental restoration. Graphical abstract

Sulfides should be removed before the recovery of cassiterite from tin-rich minerals due to their similarity in flotation properties. However, the traditional methods used have low selectivity. Therefore, moderately thermophilic microorganisms were used to desulfurize tin ore in this study, and the success of the microbial community was investigated. The bio-desulfurization rate reached 90% on the 10th day using the mixed culture of Leptospirillum ferriphilum (L. ferriphilum), Sulfobacillus thermosulfidooxidans (S. thermosulfidooxidans), and Acidithiobacillus caldus (A. caldus), while the pure culture needs at least 14 days. The results of X-ray Diffraction (XRD) and Inductively Coupled Plasma show that the sulfides were nearly fully solubilized. XRD results showed no pyrite in the residue, indicating that pyrite was almost fully removed while cassiterite was enriched compared with the original minerals. The high-throughput sequencing analysis showed that S. thermosulfidooxidans were the predominant species during the early bioleaching period, and L. ferriphilum were the predominant species in the following period. A. caldus is consistently detected and accounts for 30–50% of the different growth stages. This study supplied a potentially practical application for the desulfurization in tin ore.