一株酚酸类物质高效降解细菌BX29的筛选鉴定及其对人参连作土壤中苯甲酸降解效果

Screening and identification of a highly efficient phenolic acid-degrading bacterium BX29 and evaluation of its degradation effect on benzoic acid in the continuous cropping soil of ginseng

摘要:

背景 人参种植过程中根系分泌的化感自毒物质是造成人参连作障碍的重要因子之一，其中苯甲酸是人参连作土壤里普遍存在的一种主要酚酸类自毒物质，利用微生物降解菌降解土壤中的酚酸类物质进而缓解人参连作障碍是有效途径。目的 通过筛选能有效降解人参连作土壤中酚酸类物质的细菌，为缓解人参连作障碍提供新的菌种资源。方法 研究采用富集驯化再分离法，从98份人参连作土壤样品中分离降解菌株，利用高效液相色谱法检测菌株对苯甲酸及其他酚酸类物质的降解能力，结合形态学特征观察、生理生化指标测定和16S rRNA基因序列分析确定高效降解菌株分类地位，并通过田间试验评价其对人参连作土壤中苯甲酸的降解能力。结果 通过富集驯化再分离法共分离获得132株细菌，经过初筛和复筛试验最终筛选获得1株对苯甲酸及肉桂酸这2种酚酸类物质均具有高效降解能力的细菌BX29，室内条件下72 h对200 mg/L苯甲酸和肉桂酸的降解率均达到90%以上，经鉴定其为1株短稳杆菌(Empedobacter brevis)。田间应用效果评价试验表明，在连作人参3年的土壤中施用8.0×10⁷-8.0×10⁹ CFU/mL的菌株BX29发酵液750 mL/m²，施用30 d和120 d后对土壤中苯甲酸的降解率分别达到42.88%-47.43%和39.51%-58.84%，人参增产率达到26.61%-47.88%，并且对人参根部农艺性状、土壤酶活性均有一定促进作用。结论 研究结果丰富了酚酸类物质降解菌的微生物资源库，在短稳杆菌BX29的开发利用及缓解人参连作障碍方面具有潜在的利用价值，对人参产业可持续发展具有重要意义。

Abstract:

Background During ginseng cultivation, allelopathic autotoxins secreted by the root system are one of the key factors contributing to the continuous cropping obstacles of ginseng. Benzoic acid (BA) is a common phenolic acid autotoxin in the continuous cropping soil of ginseng. It is an effective way to use bacteria to degrade phenolic acids in the soil and then alleviate the continuous cropping obstacles of ginseng.Objective To provide new strain resources for alleviating the continuous cropping obstacles by screening the bacteria that can effectively degrade phenolic acids in the continuous cropping soil of ginseng.Methods Ninety-eight rhizosphere soil samples were collected from the areas with continuous cropping of ginseng for the enrichment, domestication, and isolation of strains. High performance liquid chromatography (HPLC) was employed to assess the degradation efficiency of each strain for BA and other phenolic acids. The taxonomic status of a highly efficient degrading strain was determined by combining the observation of morphological characteristics, physiological-biochemical profiling, and the analysis of 16S rRNA gene sequences. Meanwhile, the field degradation efficacy of this strain was evaluated.Results A total of 132 bacterial isolates were obtained, among which strain BX29 was ultimately screened out as a highly efficient degrader of both BA and cinnamic acid through preliminary and secondary screening. Under indoor conditions, the degradation rates of strain BX29 for both BA and cinnamic acid (200 mg/L) exceeded 90% after 72 h, and this strain was identified as Empedobacter brevis (GenBank accession number: PQ892129). Field application trials demonstrated that in the soils with three-year continuous cropping of ginseng, the degradation rates of the fermentation broth of strain BX29 (8.0×10⁷-8.0×10⁹ CFU/mL) at 750 mL/m² for BA were 42.88%-47.43% on day 30 and 39.51%-58.84% on day 120 post-application. Additionally, the application increased the ginseng yield by 26.61%-47.88%, while improving the root agronomic traits and soil enzyme activities.Conclusion The results enrich the microbial resource pool of phenolic acid-degrading bacteria. This study has potential value in the development and utilization of E. brevis BX29 and alleviation of the continuous cropping obstacles of ginseng and is of great significance to the sustainable development of the ginseng industry.