In this study, a total 30 rhizobacterial isolates were screened out based on resistance against different concentrations of mercuric chloride (HgCl₂), growth on nitrogen-free mannitol (NFM) and production of indole-3-acetic acid (IAA). The biochemical and plant growth promoting characterization of selected isolates was performed by different biochemical tests. Out of 30, six isolates, UM-3, AZ-5, UM-7, UM-11, UM-26, and UM-28 showed resistance at 30 µg/ml HgCl₂, pronounced growth on NFM and high production of IAA as 18.6, 16.7, 16, 18.7, 14, and 16 µg/ml, respectively (P < 0.05). The 16S rDNA ribotyping and phylogenetic analysis of selected bacterial isolates were performed and characterized as Exiguobacterium sp. UM-3 (KJ736011), Bacillus thuringiensis AZ-5 (KJ675627), Bacillus subtilis UM-7 (KJ736013), Enterobacter cloacae UM-11 (KJ736014), Pseudomonas aeruginosa UM-26 (KJ736016), P. aeruginosa UM-28 (KJ736017) and Bacillus pumilus UM-16 (KJ736015) used as negative control. B. thuringiensis AZ-5 showed high resistance against 30 µg/ml of HgCl₂ due to the presence of merB gene. The structural determination of MerB protein was carried out using bioinformatics tools, i.e., Protparam, Pfam, InterProScan, STRING, Jpred4, PSIPRED, I-TASSER, COACH server and ERRAT. These tools predicted the structural based functional homology of MerB protein (organomercuric lyase) in association with MerA (mercuric reductase) in bacterial Hg-detoxification system.

在本研究中，根据对不同浓度氯化汞 (HgCl ₂ ) 的抗性、对无氮甘露醇 (NFM) 的生长和吲哚-3-乙酸 (IAA) 的产生，共筛选出 30 株根际细菌分离株。所选分离株的生化和植物生长促进特性通过不同的生化测试进行。在 30 个分离株中，UM-3、AZ-5、UM-7、UM-11、UM-26 和 UM-28 六个分离株在 30 µg/ml HgCl _{2 下}显示出抗性，在 NFM 上显着生长和高产 IAA分别为 18.6、16.7、16、18.7、14 和 16 µg/ml ( P  < 0.05)。对选定的细菌分离株进行了 16S rDNA 核糖体分型和系统发育分析，并将其表征为Exiguobacterium sp。UM-3 (KJ736011),苏云金芽孢杆菌AZ-5（KJ675627），枯草芽孢杆菌UM-7（KJ736013），阴沟肠杆菌UM-11（KJ736014），铜绿假单胞菌UM-26（KJ736016），铜绿假单胞菌UM-28（KJ736017）和短小芽孢杆菌UM- 16 (KJ736015) 用作阴性对照。由于mer的存在，苏云金芽孢杆菌AZ-5 对 30 µg/ml HgCl ₂表现出高抗性B基因。MerB 蛋白的结构测定使用生物信息学工具进行，即 Protparam、Pfam、InterProScan、STRING、Jpred4、PSIPRED、I-TASSER、COACH 服务器和 ERRAT。这些工具预测了细菌汞解毒系统中 MerB 蛋白（有机汞裂解酶）与 MerA（汞还原酶）相关的基于结构的功能同源性。