芘降解菌Pseudomonas sp.PR3的植物促生特性及其对芘胁迫下水稻生长的影响

Effects of Pseudomonas sp.PR3,a Pyrene-degrading Bacterium with Plant Growth-promoting Properties,on Rice Growth Under Pyrene Stress

农田中不断积累的多环芳烃不仅严重影响作物生长,同时增加粮食安全风险。筛选兼具促进植物生长特性和降解污染物功能的微生物菌株是解决上述问题的一种有效手段。从油田附近生长的植物根表分离得到一株具有芘降解能力,同时还具有溶磷、产吲哚乙酸和铁载体等植物促生特性的菌株PR3,经16S rDNA序列同源性分析确定为假单胞菌(Pseudomonas sp.)。菌株PR3在无机盐培养液中生长14 d后,对芘(20 mg/L)的降解率可达94%,对萘(50 mg/L)、菲(50 mg/L)、苯并(a)芘(10 mg/L)的降解率也分别达到92%,84%和47%。同时,该菌株7 d内最大溶磷量为756.25 mg/L,2 d内IAA合成量可达14.46 mg/L,4 d内生成铁载体的活性单位可达58.53%。在不同芘污染浓度处理下的盆栽实验表明,接种PR3可有效促进水稻生长并提高根际土壤中芘的降解,去除率可达72.02%-86.22%,同时显著降低水稻根及地上部中的芘含量,分别为21.81%-53.01%和49.81%-57.17%。因此,菌株PR3有助于实现芘污染土壤的生态修复以及降低作物芘暴露的风险。

The accumulation of polycyclic aromatic hydrocarbons(PAHs)in farmland not only seriously hinder crop growth,but also increase food security risks.Screening the microorganisms with both the functions of promoting plant growth and degrading pollutants is an effective means to solving the above problems.Strain PR3 was isolated from the root surface of plants growing near the oil field,which had the ability of degrading pyrene,and also showed the properties of promoting plant growth like phosphorus dissolution,indole acetic acid and siderophore production.The results of 16S rDNA sequence analysis showed that the strain was classified as Pseudomonas sp.After growing in PMM medium containing 20 mg/L pyrene for 14 d,the degradation rate of pyrene by strain PR3 reached 94%.The degradation rates of naphthalene(50 mg/L),phenanthrene(50 mg/L)and benzo(a)pyrene(10 mg/L)at 14 d were 92%,84% and 47%,respectively.Furthermore,the maximum dissolved phosphorus amount of strain PR3 was 756.25 mg/L in 7 d,the synthesis amount of IAA in 2 d was up to 14.46 mg/L,and the synthetic siderophore activity unit in 4 d reached 58.53%.Greenhouse pot experiments under different pyrene contamination concentration demonstrated that the inoculation of strain PR3 significantly improved the growth of rice and increased the degradation of pyrene near rhizosphere,and the removal rate reached 72.02%-86.22%.Meanwhile,the pyrene contents in the roots and shoots decreased by 21.81%-53.01% and 49.81%-57.17%,respectively.These results indicated that strain PR3 could contribute to the ecological remediation of pyrene-contaminated soil and reduce the risk of pyrene exposure to crops.