金霉素添加对有机培肥土壤中磷循环微生物介导的磷素转化和有效性的影响

Effects of chlortetracycline addition on phosphorus transformation and availability mediated by phosphorus cycling microorganisms in soil applied with organic fertilizer

摘要:

【目的】探究不同浓度金霉素的添加对有机培肥土壤中参与无机磷溶解和有机磷矿化微生物群落特征及其介导的土壤磷素转化和有效性机制的影响。【方法】选取重庆市潼南区紫色土为基质土进行盆栽试验，外源添加有机肥(鸡粪)，设置3个浓度的金霉素处理：不添加金霉素(0.0 mg/kg,No-CTC)，低浓度金霉素(0.1 mg/kg,Low-CTC)，高浓度金霉素(4.0 mg/kg,High-CTC)处理，在辣椒(‘辛香8号’)种植后第7天和第30天采集土样，利用Real-time qPCR、Illumina Miseq高通量测序技术，结合基于生物有效性磷组分(biologically based phosphorus,BBP)的磷分级等方法，探究不同浓度金霉素添加对无机磷溶解和有机磷矿化关键基因(分别为pqqC和phoD基因)细菌的群落特征及其介导的土壤磷素转化机制的影响。【结果】在第7天仅高浓度金霉素处理增加了土壤Citrate-P和Enzyme-P含量，相对于未添加金霉素分别增加了8.2%和44.0%；高、低浓度金霉素处理在第30天均增加了Enzyme-P含量，相较于未添加金霉素处理分别增加了65.6%和44.0%。金霉素抑制了土壤碱性磷酸酶(alkaline phosphatase,ALP)活性，显著影响了含pqqC和phoD基因细菌的群落结构。基于Mantel检验结果表明，第7天Citrate-P与含pqqC基因的优势物种假单胞菌属(Pseudomonas)、地嗜皮菌属(Geodermatophilus)和糖丝菌属(Saccharothrix)显著相关，而含phoD基因的优势物种慢生根瘤菌属(Bradyrhizobium)、剑菌属(Ensifer)和斯克尔曼氏菌属(Skermanella)与Enzyme-P显著相关，随着处理时间的增加，其相关性均减弱。含pqqC基因细菌群落的网络平均度(average degree)在第7天低浓度金霉素处理时增加，高浓度时则降低，在第30天高、低浓度金霉素处理下其网络平均度均降低；然而，含phoD基因细菌群落的网络平均度在第7天随金霉素浓度增加而减弱，而第30天呈相反趋势。【结论】金霉素添加通过调控含pqqC和phoD基因细菌群落结构，以及酸、碱性磷酸酶活性，显著影响了土壤Enzyme-P，进而影响了土壤中磷素的形态和有效性。本研究加深了金霉素污染对土壤-植物系统中磷循环相关微生物群落变化的认识，对抗生素施用下土壤中养分的高效利用提供科学依据。

关键词:金霉素;有机培肥;pqqC基因;phoD基因;网络特征;有机磷矿化;无机磷溶解

Abstract:

[Objective] To explore the effects of different concentrations of chlortetracycline on the characteristics of microbial communities involved in inorganic phosphorus (Pi) dissolution and organic phosphorus (Po) mineralization in the soil applied with organic fertilizer,focusing on soil P transformation and availability.[Methods] The purple soil collected from Tongnan District of Chongqing was used for a pot experiment with the addition of chicken manure as the organic fertilizer.Three chlortetracycline treatments (No-CTC,Low-CTC,and High-CTC) were designed with the addition levels of 0.0,0.1,and 4.0 mg/kg,respectively.The soil samples were collected on days 7(D7) and 30(D30) after pepper (‘Xinxiang 8’) was planted.Real-time qPCR and Illumina MiSeq high-throughput sequencing were employed to analyze the community characteristics of the bacteria carrying the key genes (pqqC and phoD) of Pi dissolution and Po mineralization,respectively.Furthermore,the sequencing results and biologically based P (BBP) fractionation were employed to examine the effects of CTC addition on soil P transformation.[Results] High-CTC increased the content of Citrate-P and Enzyme-P by 8.2% and 44.0%,respectively,compared with No-CTC on D7.Low-CTC and High-CTC increased the content of Enzyme-P by 44.0% and 65.6%,respectively,compared with No-CTC on D30.The addition of CTC suppressed alkaline phosphatase (ALP) activity and affected the community structures of pqqC and phoD-harboring bacteria in the soil.The Mantel test results showed that Citrate-P was significantly associated with the dominant pqqC-carrying taxa Pseudomonas,Geodermatophilus,and Saccharothrix on D7.The dominant phoD-carrying taxa Bradyrhizobium,Ensifer,and Skermanella exhibited notable correlations with Enzyme-P on D7,and such correlations weakened over time.The average degree of the community network of the bacteria carrying pqqC increased in the Low-CTC treatment and decreased in the High-CTC treatment on D7.The average degree of this network decreased in High-CTC and Low-CTC treatments on D30.The average degree of the community network of the bacteria carrying phoD decreased with the increase in CTC addition on D7,while this trend was opposite on D30.[Conclusion] The addition of CTC significantly affected soil Enzyme-P by regulating the community structure ofpqqC- and phoD-carrying bacteria as well as acid phosphatase (ACP) and ALP activities,thereby affecting the P forms and availability in the soil.This study contributes to a deeper understanding of alterations in microbial communities associated with P cycling in the soil-plant system contaminated by CTC.Moreover,it lays a scientific foundation for enhancing nutrient utilization efficiency in the soil applied with antibiotics.

Key words:chlortetracycline;application with organic fertilizer;pqqC;phoD;network characteristics;organic phosphorus mineralization;inorganic phosphorus dissolution