Laboratoire d'Ecologie Microbienne, Faculté des Sciences de la Nature et de la Vie, Université de Bejaia, 06000 Bejaia, Algeria.
Laboratoire d'Ecologie Microbienne, Faculté des Sciences de la Nature et de la Vie, Université de Bejaia, 06000 Bejaia, Algeria.
J Environ Manage. 2021 Jul 1;289:112547. doi: 10.1016/j.jenvman.2021.112547. Epub 2021 Apr 8.
Heavy metals accumulation in the environment has led to a decrease in the capacity of ecosystems to sustain life as human, animal and plant health is threatened. To remedy this problem, rhizoremediation has been suggested as a solution. Legumes and rhizobia symbiotic association has captivated attention due to its involvement in the restoration of heavy-metal-contaminated sites. Thus, the aim of this study was to isolate and characterize the strains nodulating Calicotome spinosa plant that naturally occurred in two Algerian mercury mines. Fifty-four bacterial strains were isolated, then grouped into sixteen distinct BOX-PCR patterns and were genetically identified as belonging to the Bradyrhizobium genus. The studied strains were able to induce nodules on Retama monosperma, R. reatam, Lupinus albus, while no nodulation was observed in Glycine max, their symbiotic capacity was confirmed by amplifying the nodC gene. The phylogenetic analysis based on the nodC has grouped this Bradyrhizobium strains to either symbiovar genistearum or retamae. The isolates revealed diversity in terms of NaCl; pH tolerance, and phosphate solubilization. Production of siderophores was negative for these strains. All the isolated Bradyrhizobium were tolerant to both Zn and Pb in contrast they were sensitive to Cu and Cd. Interestingly, 43% of strains were tolerant to high Hg levels. Hence, some strains displayed multiple tolerances to heavy metals. Therefore, this is the first time we identify Bradyrhizobium strains originating from a North African mercury mine. This study could help to select mercury and other heavy metal-tolerant rhizobia showing an interesting potential to be used as inoculants to remediate the heavy metal soil accumulation.
重金属在环境中的积累导致生态系统维持生命的能力下降，因为人类、动物和植物的健康受到威胁。为了解决这个问题，根际修复被认为是一种解决方案。由于豆科植物与根瘤菌的共生关系参与了受重金属污染场地的修复，因此引起了人们的关注。因此，本研究的目的是从自然存在于阿尔及利亚两个汞矿的 Calicotome spinosa 植物中分离和鉴定能够结瘤的菌株。从 Calicotome spinosa 植物中分离出 54 株细菌，然后根据 BOX-PCR 聚类分析将其分为 16 个不同的聚类，通过 16S rRNA 基因序列分析，这些菌株被鉴定为 Bradyrhizobium 属。研究菌株能够在 Retama monosperma、R. reatam 和 Lupinus albus 上诱导结瘤，但在 Glycine max 上没有观察到结瘤，通过扩增 nodC 基因证实了它们的共生能力。基于 nodC 基因的系统发育分析将这些 Bradyrhizobium 菌株分为 genistearum 或 retamae 共生型。这些分离株在 NaCl、pH 耐受和磷酸盐溶解方面表现出多样性。这些菌株的铁载体合成均为阴性。所有分离的 Bradyrhizobium 对 Zn 和 Pb 均具有耐受性，而对 Cu 和 Cd 则敏感。有趣的是，43%的菌株对高 Hg 水平具有耐受性。因此，一些菌株表现出对多种重金属的耐受性。因此，这是首次从北非汞矿中鉴定出 Bradyrhizobium 菌株。本研究有助于筛选对汞和其他重金属具有耐受性的根瘤菌，这些菌株具有作为接种剂修复重金属土壤积累的潜在用途。
