Department of Biochemistry and Biotechnology, The Islamia University of Bahawalpur, Bahawalpur, Pakistan.
Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur, Pakistan.
Arch Microbiol. 2019 Dec;201(10):1369-1383. doi: 10.1007/s00203-019-01705-0. Epub 2019 Jul 22.
Tanneries are the primary source of toluene pollution in the environment and toluene due to its hazardous effects has been categorized as persistent organic pollutant. Present study was initiated to trace out metabolic fingerprints of three toluene-degrading bacteria isolated from tannery effluents of Southern Punjab. Using selective enrichment and serial dilution methods followed by biochemical, molecular and antibiotic resistance analysis, isolated bacteria were subjected to metabolomics analysis. GC-MS/LC-MS analysis of bacterial metabolites helped to identify toluene transformation products and underlying pathways. Three toluene-metabolizing bacteria identified as Bacillus paralicheniformis strain KJ-16 (IUBT4 and IUBT24) and Brevibacillus agri strain NBRC 15538 (IUBT19) were found tolerant to toluene and capable of degrading toluene. Toluene-degrading potential of these isolates was detected to be IUBT4 (10.35 ± 0.084 mg/h), IUBT19 (14.07 ± 3.14 mg/h) and IUBT24 (11.1 ± 0.282 mg/h). Results of GC-MS analysis revealed that biotransformation of toluene is accomplished not only through known metabolic routes such as toluene 3-monooxygenase (T3MO), toluene 2-monooxygenase (T2MO), toluene 4-monooxygenase (T4MO), toluene methyl monooxygenase (TOL), toluene dioxygenase (Tod), meta- and ortho-ring fission pathways. But additionally, confirmed existence of a unique metabolic pathway that involved conversion of toluene into intermediates such as cyclohexene, cyclohexane, cyclohexanone and cyclohexanol. LC-MS analysis indicated the presence of fatty acid amides, stigmine, emmotin A and 2, 2-dinitropropanol in supernatants of bacterial cultures. As the isolated bacteria transformed toluene into relatively less toxic molecules and thus can be preferably exploited for the eco-friendly remediation of toluene.
制革厂是环境中甲苯污染的主要来源，由于甲苯具有危害性，已被归类为持久性有机污染物。本研究旨在从旁遮普南部制革厂废水中分离出的三种甲苯降解细菌中追踪代谢指纹。使用选择性富集和连续稀释方法，结合生化、分子和抗生素耐药性分析，对分离出的细菌进行代谢组学分析。细菌代谢物的 GC-MS/LC-MS 分析有助于鉴定甲苯转化产物和潜在途径。鉴定出的三种甲苯代谢细菌为芽孢杆菌 paralicheniformis 菌株 KJ-16（IUBT4 和 IUBT24）和 Brevibacillus agri 菌株 NBRC 15538（IUBT19），它们对甲苯具有耐受性，并能降解甲苯。这些分离株的甲苯降解能力分别为 IUBT4（10.35±0.084mg/h）、IUBT19（14.07±3.14mg/h）和 IUBT24（11.1±0.282mg/h）。GC-MS 分析结果表明，甲苯的生物转化不仅通过已知的代谢途径如甲苯 3-单加氧酶（T3MO）、甲苯 2-单加氧酶（T2MO）、甲苯 4-单加氧酶（T4MO）、甲苯甲基单加氧酶（TOL）、甲苯双加氧酶（Tod）、间位和邻位环裂途径来完成。但除此之外，还证实了一种独特的代谢途径的存在，该途径涉及将甲苯转化为环己烯、环己烷、环己酮和环己醇等中间体。LC-MS 分析表明，在细菌培养物的上清液中存在脂肪酸酰胺、豆甾醇、emmotin A 和 2,2-二硝基丙醇。由于分离出的细菌将甲苯转化为相对毒性较小的分子，因此可以更好地用于甲苯的环保修复。
