DataSheet_1_Unraveling the potential of bacteria isolated from the equatorial region of Indian Ocean in mercury detoxification.docx

The marine environment is most vital and flexible with continual variations in salinity, temperature, and pressure. As a result, bacteria living in such an environment maintain the adaption mechanisms that are inherent in unstable environmental conditions. The harboring of metal-resistant genes in marine bacteria contributes to their effectiveness in metal remediation relative to their terrestrial counterparts. A total of four mercury-resistant bacteria (MRB) i.e. NIOT-EQR_J7 (Alcanivorax xenomutans); NIOT-EQR_J248 and NIOT-EQR_J251 (Halomonas sp.); and NIOT-EQR_J258 (Marinobacter hydrocarbonoclasticus) were isolated from the equatorial region of the Indian Ocean (ERIO) and identified by analyzing the 16S rDNA sequence. The MRBs can reduce up to 70% of Hg(II). The mercuric reductase (merA) gene was amplified and the mercury (Hg) volatilization was confirmed by the X-ray film method. The outcomes obtained from ICP-MS validated that the Halomonas sp. NIOT-EQR_J251 was more proficient in removing the Hg from culture media than other isolates. Fourier transform infrared (FT-IR) spectroscopy results revealed alteration in several functional groups attributing to the Hg tolerance and reduction. The Gas Chromatography-Mass Spectrometry (GC-MS) analysis confirmed that strain Halomonas sp. (NIOT-EQR_J248 and NIOT-EQR_J251) released Isooctyl thioglycolate (IOTG) compound under mercury stress. The molecular docking results suggested that IOTG can efficiently bind with the glutathione S-transferase (GST) enzyme. A pathway has been hypothesized based on the GC-MS metabolic profile and molecular docking results, suggesting that the compound IOTG may mediate mercuric reduction via merA-GST related detoxification pathway.

海洋环境因盐度、温度与压力持续变化，是至关重要且动态可变的生境。栖息于此环境的细菌演化出适应不稳定环境条件的固有适应机制。相较于陆生同类细菌，海洋细菌携带的抗金属基因使其在重金属修复方面更具效能。本研究从印度洋赤道区域（ERIO）共分离得到4株耐汞细菌（mercury-resistant bacteria, MRB），分别为NIOT-EQR_J7（异种食烷菌 *Alcanivorax xenomutans*）、NIOT-EQR_J248与NIOT-EQR_J251（盐单胞菌属未定种 *Halomonas* sp.）以及NIOT-EQR_J258（解烃海杆菌 *Marinobacter hydrocarbonoclasticus*），并通过16S rDNA序列分析完成物种鉴定。这些耐汞细菌可还原高达70%的二价汞（Hg(II)）。研究扩增得到汞还原酶（merA）基因，并通过X光胶片法验证了汞（Hg）的挥发过程。电感耦合等离子体质谱（ICP-MS）的检测结果证实，盐单胞菌属未定种NIOT-EQR_J251相较于其他分离菌株，对培养基中汞的去除能力更为高效。傅里叶变换红外光谱（FT-IR）分析结果显示，多个官能团发生了变化，这与菌株的汞耐受及还原能力相关。气相色谱-质谱联用（GC-MS）分析证实，盐单胞菌属未定种菌株NIOT-EQR_J248与NIOT-EQR_J251在汞胁迫下会分泌巯基乙酸异辛酯（Isooctyl thioglycolate, IOTG）。分子对接结果表明，IOTG可与谷胱甘肽S-转移酶（GST）高效结合。本研究基于GC-MS代谢组学分析结果与分子对接数据，提出了一条假说途径：IOTG可通过merA-GST相关解毒通路介导二价汞的还原过程。