Isolation and characterization of phenanthrene-degrading bacteria from urban soil

Phenanthrene (PHE) is one of the most abundant Polycyclic Aromatic Hydrocarbons (PAHs) found in urban soil. So far, majority of microbe-mediated degradation approaches have relied on microbes isolated from polluted or mined soils. These microbes, if introduced into non-native soil, may not able to establish themselves, or alter the native microbiome of soil, making their commercial use a challenge. Therefore, this study was conducted to screen and isolate bacteria, from urban soil that degrade PHE. Degradation of 50 mg/L PHE by day 4 was highest in <i>Providencia rettgeri</i> VMP5 (98.63%) followed by <i>Bacillus tropicus</i> VMP4 (89.9%), <i>Bacillus</i> sp. VMP2 (82.63%), <i>P. stuartii</i> VMP3 (39.72%) and least <i>Dellaglioa algida</i> VMP1 (3.32%). Besides, VMP5, showed the presence of several fatty acid ethyl esters that act as biosurfactants and anti-microbial agent, which may play a crucial role in increasing its adaptability and degradation potential. VMP4 and VMP2 were also found to produce more defense compounds which may be crucial for their adaptability to PAH rich environment. Thus, VMP5, VMP4 and VMP2 showed promising remediation potential that can be further explored to develop commercially viable consortia for PHE mitigation in urban soil.

菲（Phenanthrene, PHE）是城市土壤中分布最为广泛的多环芳烃（Polycyclic Aromatic Hydrocarbons, PAHs）之一。截至目前，绝大多数微生物介导的降解策略均依赖于从污染土壤或矿区土壤中分离得到的微生物。这类微生物若被引入非原生土壤中，不仅难以成功定殖，还可能改变土壤原有的微生物组，这使其商业化应用面临诸多挑战。因此，本研究旨在从城市土壤中筛选并分离可降解PHE的细菌。截至培养第4天，初始浓度为50mg/L的PHE降解率以雷氏普罗威登斯菌（*Providencia rettgeri*）VMP5最高，达98.63%；其次为热带芽孢杆菌（*Bacillus tropicus*）VMP4（89.9%）、芽孢杆菌属（*Bacillus* sp.）VMP2（82.63%）、斯图亚特普罗威登斯菌（*P. stuartii*）VMP3（39.72%），降解率最低的为寒冷戴尔格利奥菌（*Dellaglioa algida*）VMP1（3.32%）。此外，VMP5可产生多种兼具生物表面活性剂与抗菌剂功能的脂肪酸乙酯，这类物质可能在提升其环境适应性与降解潜能方面发挥关键作用。VMP4与VMP2同样可合成较多防御类化合物，这或许对它们适应富PAHs环境至关重要。综上，VMP5、VMP4与VMP2展现出良好的修复潜力，可进一步开展研究以开发可商业化应用的菌群联合体，用于城市土壤中PHE的污染修复。