Badawy Ibrahim H, Hmed Ahmed A, Sofy Mahmoud R, Al-Mokadem Alshymaa Z
Botany and Microbiology Department, Faculty of Science, Al-Azhar University, Cairo 11884, Egypt.
Botany Department, Women's College, Ain Shams University, Cairo 11566, Egypt.
Plants (Basel). 2022 Aug 3;11(15):2018. doi: 10.3390/plants11152018.
Cadmium (Cd) and nickel (Ni) are two of the most toxic metals, wreaking havoc on human health and agricultural output. Furthermore, high levels of Cd and Ni in the soil environment, particularly in the root zone, may slow plant development, resulting in lower plant biomass. On the other hand, endophytic bacteria offer great promise for reducing Cd and Ni. Moreover, they boost plants' resistance to heavy metal stress. Different bacterium strains were isolated from tomato roots. These isolates were identified as and using 16SrDNA and were utilized to investigate their involvement in mitigating the detrimental effects of heavy metal stress. The two bacterial strains can solubilize phosphorus and create phytohormones as well as siderophores. Therefore, the objective of this study was to see how endophytic bacteria ( and ) affected the mitigation of stress from Cd and Ni in tomato plants grown in 50 μM Cd or Ni-contaminated soil. According to the findings, Cd and Ni considerably lowered growth, biomass, chlorophyll (Chl) content, and photosynthetic properties. Furthermore, the content of proline, phenol, malondialdehyde (MDA), HO, OH, O, the antioxidant defense system, and heavy metal (HM) contents were significantly raised under HM-stress conditions. However, endophytic bacteria greatly improved the resistance of tomato plants to HM stress by boosting enzymatic antioxidant defenses (i.e., catalase, peroxidase, superoxide dismutase, glutathione reductase, ascorbate peroxidase, lipoxygenase activity, and nitrate reductase), antioxidant, non-enzymatic defenses, and osmolyte substances such as proline, mineral content, and specific regulatory defense genes. Moreover, the plants treated had a higher value for bioconcentration factor (BCF) and translocation factor (TF) due to more extensive loss of Cd and Ni content from the soil. To summarize, the promotion of endophytic bacterium-induced HM resistance in tomato plants is essentially dependent on the influence of endophytic bacteria on antioxidant capacity and osmoregulation.
镉（Cd）和镍（Ni）是毒性最强的两种金属，对人类健康和农业产出造成严重破坏。此外，土壤环境中，尤其是根区的高含量镉和镍可能会减缓植物生长，导致植物生物量降低。另一方面，内生细菌在降低镉和镍含量方面具有巨大潜力。此外，它们还能增强植物对重金属胁迫的抗性。从番茄根部分离出不同的细菌菌株。利用16S rDNA将这些分离菌株鉴定为[具体菌株名称未给出]，并用于研究它们在减轻重金属胁迫不利影响方面的作用。这两种细菌菌株能够溶解磷并产生植物激素以及铁载体。因此，本研究的目的是观察内生细菌（[具体菌株名称未给出]）对生长在50 μM镉或镍污染土壤中的番茄植株镉和镍胁迫缓解的影响。研究结果表明，镉和镍显著降低了植株的生长、生物量、叶绿素（Chl）含量和光合特性。此外，在重金属胁迫条件下，脯氨酸、酚类、丙二醛（MDA）、羟基自由基（HO·）、超氧阴离子自由基（O₂·）、抗氧化防御系统和重金属（HM）含量显著升高。然而，内生细菌通过增强酶促抗氧化防御（即过氧化氢酶、过氧化物酶、超氧化物歧化酶、谷胱甘肽还原酶、抗坏血酸过氧化物酶、脂氧合酶活性和硝酸还原酶）、抗氧化非酶促防御以及脯氨酸等渗透调节物质、矿物质含量和特定的调节防御基因，极大地提高了番茄植株对重金属胁迫的抗性。此外，由于土壤中镉和镍含量的大量减少，处理后的植株生物富集系数（BCF）和转运系数（TF）值更高。总之，内生细菌诱导番茄植株对重金属抗性的提升在本质上依赖于内生细菌对抗氧化能力和渗透调节的影响。
