接种混合功能细菌降低黑麦草体内菲和芘污染的机理初探

本研究通过批量降解试验,探讨了功能菌株Massilia sp. Pn2和Mycobacterium flavescens 033降解菲和芘的基本动力学过程和规律;重点采用温室盆栽试验,研究了接种混合菌株对黑麦草体内PAHs含量及多酚氧化酶(PPO)和过氧化物酶(POD)活性的影响.结果表明,菌株Pn2和033可以分别利用菲和芘作为碳源和能源进行生长;在30℃、pH=7.0条件下,菌株Pn2和033对100 mg·L~(-1)菲和50 mg·L~(-1)芘的降解率分别高达99.7%和98.3%,降解半衰期分别为0.34 d和0.95 d(R~20.98).与接种灭活混合菌株对比,接种混合菌株Pn2和033显著地降低了黑麦草体内菲和芘的含量和积累量(p0.05),并阻控菲和芘由黑麦草根向茎叶转移.同时,接种混合菌株Pn2和033显著地提高了黑麦草根和茎叶中POD(p0.05)活性,该酶能够促进黑麦草体内超氧自由基的清除,并保护细胞免受PAHs损伤,进而影响PAHs在黑麦草体内的代谢过程.研究结果为阐明接种混合功能菌降低植物体内PAHs污染的作用机理提供了一定的参考价值.

Inoculation with mixed PAH-degrading bacteria mitigates the contamination of phenanthrene and pyrene in ryegrass (Lolium multiflorum Lam) using greenhouse pot experiments

Polycyclic aromatic hydrocarbons (PAHs) are a category of persistent organic contaminants extensively found in soil environments. PAHs can be taken up, accumulated, and translocated by plants, which pose a significant risk worldwide to food safety and hence human health due to their high bio-accumulation, carcinogenicity, toxicity, and biodegradation-resistant. It is well documented that inoculation of PAH-degrading bacterium is a simple and effective strategy for mitigating the contamination of PAHs in plants. However, microscopic information is available on inoculation with mixed PAH-degrading bacteria to regulate plant PAH contamination and the activities of related to metabolic enzymes in plants. In this study, the biodegradation kinetics and regularity of phenanthrene and pyrene were respectively investigated using Massilia sp. Pn2 and Mycobacterium flavescens 033 in in vitro. In particular, greenhouse pot experiments of inoculated two PAH-degrading bacteria were conducted to reduce PAHs residues in ryegrass (Lolium multiflorum Lam), and the effect of strains Pn2 and 033 on the activities of polyphenol oxidase (PPO) and peroxidase (POD) was also explored in in vivo. Results indicated that both strains Pn2 and 033 could use phenanthrene and pyrene as the sources of carbon and energy for growth of tested strains. They were effective in biodegrading PAHs in in vitro, and the biodegradation rates of phenanthrene and pyrene were respectively 99.7% and 98.3%, the half-life values were respectively 0.34 d and 0.95 d (R²>0.98). Compared with the mixed dead bacteria control (CRD), inoculation with mixed PAH-degrading strains altered the migration and transformation of PAHs in soil-ryegrass systems, and reduced the concentration and accumulation of PAHs into ryegrass roots and shoots (p<0.05). In addition, inoculation with mixed PAH-degrading bacteria also impacted the activities of PPO (p>0.05) and POD (p<0.05) in plants. Thus, strains Pn2 and 033 could be a useful bacterial resource for reducing PAHs contents via regulating the activity of POD inside plants. These findings provide a novel perspective in utilizing plant-bacteria partnerships to reduce plan PAH residues and regulate the activities of enzymes in plants, with ultimate goal of protecting agricultural products safety and human health.