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    望天树人工林根际溶磷细菌的筛选及溶磷特性

    Screening and characteristics of phosphorus solubilizing bacteria in the rhizosphere of Parashorea chinensis plantation

      摘要
    • 摘要:
        目的  望天树是我国特有的濒危一级保护树种，人工林栽培是扩大其种群数量的重要手段，磷素供应是林木生长发育的主要影响因子，而溶磷菌在磷转化中起到重要作用。本研究从不同林龄望天树人工林根际土壤中筛选高效溶磷细菌，探究其在不同培养条件下的溶磷特点，以期为望天树微生物肥料的开发与应用提供菌种资源和理论依据。
        方法  （1）利用无机磷固体培养基从不同林龄望天树林分根际土中分离筛选溶磷细菌，挑选4株高效溶磷菌，结合生理生化试验和16SrDNA基因序列对其进行鉴定。（2）通过检测溶磷动态，研究溶磷细菌溶磷量与菌液pH的相关关系。（3）采用单因素试验探究高效溶磷菌在不同环境因子和营养因子下的溶磷特性。
        结果  （1）共分离筛选出18株溶磷菌，其中溶磷能力较强菌株为P4、P8、P12和P30（溶磷量分别为552.87、559.78、548.53、598.89 mg/L）。（2）经过形态观察、生理生化鉴定及系统发育树分析，菌株P8鉴定为唐菖蒲伯克霍尔德菌，P4和P12鉴定为洋葱伯克霍尔德菌，P30鉴定为蜡状芽孢杆菌。（3）P4、P8、P12和P30菌株的溶磷量与培养液pH值之间均存在极显著的负相关性（P < 0.01），相关系数分别为−0.995、−0.990、−0.985和−0.997。（4）单因素试验结果显示：各溶磷菌株在温度为30 ~ 35 ℃，pH为5.5 ~ 8.5，NaCl质量分数为0 ~ 2.5%，碳（C）源为蔗糖、乳糖和葡萄糖，氮（N）源为草酸铵和硫酸铵时，表现出较好的溶磷效果；菌株P30、P12和P4最适C∶N为20∶1，P8最适合C∶N为40∶1；菌株P12最佳磷源为FePO4，P30、P8和P4最佳磷源均为Ca3(PO4)2。
        结论  不同培养条件会显著影响溶磷细菌的溶磷能力，筛选得到的4株高效溶磷菌具有良好的溶磷能力，且能够溶解多种难溶性无机磷酸盐，可用于望天树专用微生物肥料的研发，具有良好的应用潜力。

       

      Abstract:
        Objective  The Parashorea chinensis is an endemic and endangered species in China, and it is classified as a class Ⅰ protected wild plant. Plantation cultivation is an important means to expand its populations. Phosphorus (P) supply is a major influence on tree growth and development, and P dissolving bacteria plays an important role in P transformation. This research aimed to screen high-efficient phosphate-solubilizing bacteria (PSB) from the rhizosphere soil of P. chinensis plantations of different ages, and explore its P-solubilizing characteristics, so as to provide bacterial resources and culture conditions for the development of microbial fertilizer suitable of P. chinensis.
        Method  (1) PSB was isolated and screened from the rhizosphere soil of P. chinensis in different ages by inorganic P solid medium. The physiological and biochemical tests and 16S rDNA gene sequence were used to further identify 4 strains of PSB. (2) The relationship between the amount of P dissolved by PSB and the pH of the bacterial solution was studied by detecting the dynamics of P solubilization. (3) A single factor experiment was conducted to investigate the P-solubilizing characteristics of high efficiency PSB under different environmental and nutritional factors.
        Result  (1) A total of 18 strains of phosphorus solubilizing bacteria were isolated and screened, and the 4 strains with the strongest P-solubilizing capacity were P4, P8, P12 and P30 (P-solubilizing capacity was 552.87, 559.78, 548.53 and 598.89 mg/L, respectively). (2) Strain P8 was identified as Burkholderia gladioli, P4 and P12 as Burkholderia cepacia, and P30 as Bacillus cereus by physiological, biochemical identification and combined with phylogenetic tree analysis. (3) There was a highly significant (P < 0.01) negative correlation between the pH of the cultures and the amount of phosphorus dissolved by the P4, P8, P12 and P30 strains, with correlation coefficients of −0.995, −0.990, −0.985 and −0.997, respectively. (4) The results of single factor test showed that the PSBs had the preferable P-solubilizing effects at a temperature of 30−35 ℃, the pH of 5.5−8.5, the NaCl mass fraction was 0−2.5%, the carbon (C) sources were sucrose, lactose and glucose, and the nitrogen (N) sources were ammonium oxalate and ammonium sulfate. The optimal C∶N of strain P30, P12 and P4 was 20∶1, and that of P8 was 40∶1. The optimal P source for strain P12 was FePO4, and Ca3(PO4)2 for P30, P8 and P4.
        Conclusion  The P-solubilizing ability of PSBs can be significantly affected under different culture conditions. The 4 strains of high efficiency PSB have preferable P-solubilizing ability, which can dissolve a variety of insoluble inorganic phosphates. Therefore, it is expected to provide germplasm resources for the development of high-efficiency microbial phosphate fertilizers with a good application potential.

       

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