Flores-Gallegos Fanny A, García-Guevara Fernando, Vega-Alvarado Leticia, Lara Paloma, Jiménez-Jacinto Verónica, Juárez Katy
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México.
Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de Mexico, México.
Environ Sci Pollut Res Int. 2025 Jul;32(33):19885-19899. doi: 10.1007/s11356-025-36804-7. Epub 2025 Aug 11.
Excess industrial Cr(VI) waste and its improper disposal have resulted in the contamination of diverse environments, including soils and aquifers. To contend with high concentration of Cr(VI), a dangerous mutagen and oxidizing agent, diverse bacteria have developed a broad spectrum of metabolic strategies, mainly through chromate efflux pumps and reduction of Cr(VI) to Cr(III), which is less toxic and unable to cross biological membranes. In this study, we performed an in situ biostimulation assay in a highly alkaline and saline soil from a long-term contaminated site in Guanajuato, México. Four percent molasses was an effective treatment in promoting the Cr(VI) reduction by indigenous microorganisms. Initial Cr(VI) concentration was 5.6 to 12.4 g per kg of soil; After biostimulation assay (20 days), Cr(VI) was reduced from 0.75 to 3.02 g per kg of soil. DNA and RNA extraction from biostimulated samples was performed to carry out metagenomic and metatranscriptomic studies. Furthermore, 16S rDNA V3 and V4 amplicons were sequenced using illumina MiSeq technology complementing the study. The results showed an enrichment at Class level of Gammaproteobacteria, Alphaproteobacteria, Actinobacteria, Nitriliruptoria and Bacilli. The enrichment of Halomonas spp. during the biostimulation assay was remarkable, reaching 92% of the population and becoming the most dominant genus. On the other hand, comparative metagenomic and metatranscriptomic analysis was carried out in order to know the whole microbial population and the genes expressed during the reduction of Cr(VI) to Cr(III). We identified reductase genes associated with various bacterial groups. Interestingly, all the expressed reductase genes were exclusively from the genus Halomonas, which are related with our taxonomic assignment analysis. This study improves our understanding of the response of bacterial communities to high exposure to chromate and offers an alternative to the restoration of environments severely contaminated with this powerful toxic agent.
工业六价铬废弃物过量及其不当处置导致了包括土壤和含水层在内的多种环境受到污染。为了应对高浓度的六价铬（一种危险的诱变剂和氧化剂），多种细菌已开发出广泛的代谢策略，主要是通过铬酸盐外排泵以及将六价铬还原为毒性较小且无法穿过生物膜的三价铬。在本研究中，我们在墨西哥瓜纳华托一个长期受污染场地的高碱性和高盐土壤中进行了原位生物刺激试验。4%的糖蜜是促进本地微生物还原六价铬的有效处理方法。初始六价铬浓度为每千克土壤5.6至12.4克；生物刺激试验（20天）后，六价铬从每千克土壤0.75克降至3.02克。对生物刺激后的样品进行DNA和RNA提取，以开展宏基因组学和宏转录组学研究。此外，使用Illumina MiSeq技术对16S rDNA V3和V4扩增子进行测序，以补充该研究。结果显示，γ-变形菌纲、α-变形菌纲、放线菌纲、腈裂解菌目和芽孢杆菌纲在类水平上富集。在生物刺激试验期间，嗜盐单胞菌属的富集显著，占种群的92%，成为最主要的属。另一方面，进行了比较宏基因组学和宏转录组学分析，以了解整个微生物群落以及六价铬还原为三价铬过程中表达的基因。我们鉴定出与各种细菌类群相关的还原酶基因。有趣的是，所有表达的还原酶基因都仅来自嗜盐单胞菌属，这与我们的分类分配分析结果相符。本研究增进了我们对细菌群落对高暴露铬酸盐的反应的理解，并为修复受这种强效有毒物质严重污染的环境提供了一种替代方法。
