Department of Biochemistry, Faculty of Science, Auckland Park Campus, University of Johannesburg, Johannesburg 2092, South Africa.
DST-NRF Centre of Excellence for Biomedical Tuberculosis Research, South African Medical Research Council Centre for Tuberculosis Research, Division of Molecular Biology and Human Genetics, Faculty of Medicine and Health Sciences, Tygerberg Campus, Stellenbosch University, Cape Town 7505, South Africa.
Int J Environ Res Public Health. 2021 Jan 23;18(3):997. doi: 10.3390/ijerph18030997.
is an indigenous southern African tree species, a metal hyperaccumulator that has been used as a phytoextraction option for tailing dams in Johannesburg, South Africa. In hyperaccumulators, metal detoxification has also been linked or attributed to the activities of endophytes, and, in this regard, metal detoxification can be considered a form of endophytic behavior. Therefore, we report herein on the identification of proteins that confer heavy metal resistance, the in vitro characterization of heavy metal resistance, and the production of plant growth-promoting (PGP) volatiles by MAMP 4754. Multigenome comparative analyses of MAMP 4754 against eight other endophytic strains led to the identification of zinc, copper, and nickel resistance proteins in the genome of this endophyte. The maximum tolerance concentration (MTC) of this strain towards these metals was also investigated. The metal-exposed cells were analyzed by transmission electron microscopy (TEM). The ethyl acetate and chloroform extracts (1:1 /) of heavy metal untreated MAMP 4754 were also screened for the production of PGP compounds by Gas Chromatography-Mass Spectroscopy (GC/MS). The MTC was recorded at 15 mM, 4 mM, and 12 mM for zinc, copper, and nickel, respectively. The TEM analysis showed the accumulation of metals in the intracellular environment of MAMP 4754, while the GC/MS analysis revealed several plant growth-promoting compounds, including alcohols, phthalate esters, alkenes, ketones, sulfide derivatives, phenols, and thiazoles. Our findings suggest that the genetic makeup of MAMP 4754 encodes heavy metal resistant proteins that indicate hyperaccumulator-specific endophytic behavior and the potential for application in bioremediation. The production of plant growth-promoting volatiles in pure culture by MAMP 4754 is a characteristic feature for plant growth-promoting bacteria.
是一种土生土长的南非树种，是一种金属超富集植物，已被用作南非约翰内斯堡尾矿坝的植物提取选项。在超富集植物中，金属解毒也与内生菌的活动有关或归因于内生菌的活动，在这方面，金属解毒可以被认为是一种内生行为。因此，我们在此报告了鉴定赋予重金属抗性的蛋白质、体外表征重金属抗性以及由 MAMP 4754 产生植物生长促进（PGP）挥发物的情况。MAMP 4754 与其他八种内生菌株的多基因组比较分析导致在该内生菌的基因组中鉴定出锌、铜和镍抗性蛋白。还研究了该菌株对这些金属的最大耐受浓度（MTC）。用透射电子显微镜（TEM）分析了暴露于金属的细胞。还通过气相色谱-质谱联用（GC/MS）筛选未经金属处理的 MAMP 4754 的乙酸乙酯和氯仿提取物（1:1/）是否产生 PGP 化合物。MTC 分别记录为锌、铜和镍的 15 mM、4 mM 和 12 mM。TEM 分析显示金属在 MAMP 4754 的细胞内环境中积累，而 GC/MS 分析显示出几种植物生长促进化合物，包括醇、邻苯二甲酸酯、烯烃、酮、硫化物衍生物、酚和噻唑。我们的研究结果表明，MAMP 4754 的遗传组成编码了重金属抗性蛋白，表明超富集植物的特定内生行为和在生物修复中的应用潜力。MAMP 4754 在纯培养中产生植物生长促进挥发物是植物生长促进细菌的特征。
