三七皂苷类自毒物质降解细菌分离及其降解特性

Isolation and characterization of saponins-degrading bacterial strains from Panax notoginseng

关键词:  三七, 自毒作用, 自毒物质, 皂苷, 生物降解

Key words:  Panax notoginseng, autotoxicity, allelochemical, saponins, biodegradation

摘要:

三七是我国的名贵药材,但由于连作障碍发生严重,因此土壤中自毒物质的积累成为导致三七连作障碍发生的主要原因之一。生物降解土壤中的自毒物质是缓解连作障碍的有效措施,为筛选并利用降解菌使土壤中皂苷类自毒物质快速消减,该研究以皂苷类自毒物质为筛选靶标,采用富集和驯化策略,从连作三七根际土壤中分离、筛选三七皂苷类自毒物质降解细菌,结合16S rRNA基因测序对高活性菌株进行分类鉴定,并对筛选得到的高活性菌株SC3的降解特性进行了研究。结果表明:(1)从三七根际土壤中成功分离出8株潜在自毒物质降解细菌,初筛评价结果显示SC3菌株对三七总皂苷的降解率最高,达87.42%。(2)通过16S rRNA基因序列分析,编号SC3的高活性菌株被鉴定为寡养单胞菌属(Stenotrophomonas)细菌。(3)在相同培养条件下,菌株SC3对单体皂苷Rb₁的降解效果强于对Rg₁的降解。(4)在液体培养条件下,底物浓度、接种量和培养温度均会显著影响SC3菌株对单体皂苷Rb₁的降解效果。综上表明,采用富集和驯化策略可以有效筛选自毒物质降解细菌,SC3菌株具有消除连作土壤中皂苷类自毒物质的潜力。该研究结果为连作土壤修复提供了生物资源,并为今后深入研究皂苷降解机制提供了理论依据。

Abstract:

Panax notoginseng is a valuable Chinese herb in China, and the root should be harvested between three and seven years after planting it. However, the growth of P. notoginseng is frequently hindered due to replanting failure. There have been numerous studies proving that the accumulation of allelochemicals in the soil is considered to be one of the reasons for the replanting failure of P. notoginseng. Biodegradation of allelochemical in soil has been shown to be an effective measure to alleviate continuous cropping obstacles, so screening allelochemical-degrading bacteria could provide biological resources for soil remediation. Based on this, this study adopted a research strategy of enrichment and domestication to isolate and screen saponin-degrading bacteria from the rhizosphere soil of P. notoginseng, which had been grown continuously for 3 years and more. Also, the highly active strains were identified by 16S rRNA gene analysis. In addition, the effect of highly active strain SC3 on degrading allelochemicals under different conditions was studied by HPLC. The results were as follows:(1)Eight strains of potentially degrading bacteria were successfully isolated from the rhizosphere soil of P. notoginseng. The results of the initial screening evaluation showed that strain SC3 had the best biodegradation effect on total saponins with 87.42% degradation rate.(2)Strain SC3 was identified as Stenotrophomonas sp. based on 16S rRNA gene analysis coupled with physiological and biochemical analyses.(3)The biodegradation of ginsenoside Rb₁ by strain SC3 was stronger than its degradation of ginsenoside Rg₁ under the same culture conditions.(4)The degradation of ginsenoside Rb₁ by SC3 strain under liquid culture conditions was significantly affected by different factors, such as substrate concentration, inoculum amount and incubation temperature. This study shows that the enrichment and domestication strategy can effectively screen allelochemical-degrading bacteria, and a possible application of strain SC3 in the bioremediation of saponin contamination in agricultural environments.