Laboratorio de Biología de Bacterias y Hongos Filamentosos, Unidad Académica de Ciencias Biológicas, Universidad Autónoma de Zacatecas, Zacatecas, Zacatecas, Mexico.
Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), Irapuato, Guanajuato, Mexico.
Microbiol Spectr. 2022 Oct 26;10(5):e0065622. doi: 10.1128/spectrum.00656-22. Epub 2022 Aug 18.
The environmental deterioration produced by heavy metals derived from anthropogenic activities has gradually increased. The worldwide dissemination of toxic metals in crop soils represents a threat for sustainability and biosafety in agriculture and requires strategies for the recovery of metal-polluted crop soils. The biorestoration of metal-polluted soils using technologies that combine plants and microorganisms has gained attention in recent decades due to the beneficial and synergistic effects produced by its biotic interactions. In this context, native and heavy metal-resistant plant growth-promoting bacteria (PGPB) play a crucial role in the development of strategies for sustainable biorestoration of metal-contaminated soils. In this study, we present a genomic analysis and characterization of the rhizospheric bacterium Bacillus megaterium HgT21 isolated from metal-polluted soil from Zacatecas, Mexico. The results reveal that this autochthonous bacterium contains an important set of genes related to a variety of operons associated with mercury, arsenic, copper, cobalt, cadmium, zinc and aluminum resistance. Additionally, halotolerance-, beta-lactam resistance-, phosphate solubilization-, and plant growth-promotion-related genes were identified. The analysis of resistance to metal ions revealed resistance to mercury (Hg), arsenate [AsO]³, cobalt (Co), zinc (Zn), and copper (Cu). Moreover, the ability of the HgT21 strain to produce indole acetic acid (a phytohormone) and promote the growth of Arabidopsis thaliana seedlings was also demonstrated. The genotype and phenotype of Bacillus megaterium HgT21 reveal its potential to be used as a model of both plant growth-promoting and metal multiresistant bacteria. Metal-polluted environments are natural sources of a wide variety of PGPB adapted to cope with toxic metal concentrations. In this work, the bacterial strain Bacillus megaterium HgT21 was isolated from metal-contaminated soil and is proposed as a model for the study of metal multiresistance in spore-forming Gram-positive bacteria due to the presence of a variety of metal resistance-associated genes similar to those encountered in the metal multiresistant Gram-negative Cupriavidus metallidurans CH34. The ability of B. megaterium HgT21 to promote the growth of plants also makes it suitable for the study of plant-bacteria interactions in metal-polluted environments, which is key for the development of techniques for the biorestoration of metal-contaminated soils used for agriculture.
人为活动产生的重金属导致的环境恶化逐渐加剧。有毒金属在作物土壤中的全球传播对农业的可持续性和生物安全构成了威胁，因此需要采取策略来修复受金属污染的农田土壤。近几十年来，利用植物和微生物相结合的技术进行金属污染土壤的生物修复引起了人们的关注，因为其生物相互作用会产生有益和协同的效果。在这种情况下，本地和耐重金属的植物促生菌（PGPB）在制定可持续修复受金属污染土壤的策略方面发挥着至关重要的作用。在本研究中，我们对从墨西哥萨卡特卡斯受金属污染土壤中分离到的根际细菌巨大芽孢杆菌 HgT21 进行了基因组分析和表征。结果表明，这种本土细菌含有一组与各种与汞、砷、铜、钴、镉、锌和铝抗性相关的操纵子有关的重要基因。此外，还鉴定出了耐盐性、β-内酰胺抗性、磷酸盐溶解和促进植物生长相关的基因。对金属离子抗性的分析表明，该菌株对汞（Hg）、砷酸盐[AsO]³、钴（Co）、锌（Zn）和铜（Cu）具有抗性。此外，HgT21 菌株还具有产生吲哚乙酸（一种植物激素）和促进拟南芥幼苗生长的能力。巨大芽孢杆菌 HgT21 的基因型和表型表明，它有可能被用作植物促生和耐多种金属细菌的模型。受金属污染的环境是各种适应于应对有毒金属浓度的 PGPB 的天然来源。在这项工作中，从受金属污染的土壤中分离到了芽孢杆菌属菌株 HgT21，并因其存在多种类似于耐金属革兰氏阴性菌 Cupriavidus metallidurans CH34 中遇到的金属抗性相关基因而被提议作为研究革兰氏阳性芽孢杆菌耐多种金属的模型。HgT21 促进植物生长的能力也使其适合用于研究受金属污染环境中的植物-细菌相互作用，这对于开发用于农业的受金属污染土壤的生物修复技术至关重要。
