【作者】 王菲；

【导师】 江荣风； 冯固； Michael A.Kertesz；

【作者基本信息】 中国农业大学 ， 植物营养学， 2014， 博士

【摘要】 AM真菌与细菌都是微生物中的重要功能组群,在土壤磷循环中发挥着至关重要的作用,而且两者之间的相互作用也有利于土壤磷的周转和植物磷养分的吸收,但其互作机理及其对土壤磷周转与利用的生态功能的研究还很薄弱。本论文以AM真菌与解磷细菌两种功能微生物互作机制为切入点,利用分室隔网培养体系、T-RFLP、13C-DNA-SIP、454高通量测序等微生物分子生态学技术手段,分别在生理和分子水平上研究AM真菌根外菌丝及其与细菌互作对土壤有机磷矿化与周转的调控,主要结果如下：1、铵态氮诱导的菌丝际酸化促进玉米对有机磷的吸收。与硝态氮相比,铵态氮处理显著降低了菌丝际土壤的pH,增强了土壤实际的磷酸酶活性,进而加速了土壤有机磷的矿化,促进植株对有机磷的吸收。2、菌丝际解磷细菌对根外菌丝分泌物的利用和参与土壤有机磷的周转。与单接种细菌和菌根真菌相比,双接种处理显著减少了菌丝际土壤中有机磷的含量,增加了微生物量磷的含量,AM真菌与解磷细菌互作对植物磷的吸收量没有显著贡献,双接种还抑制了AM真菌在菌丝室中的生长。利用13C-DNA-SIP技术、T-RFLP和克隆文库的分析发现,菌丝际定殖的草酸杆菌科(Oxalobacteraceae)、链霉菌科(Streptomycetaceae)和假单胞菌科(Pseudomonadaceae)的细菌被13C标记,其中包括试验中加入的已知解磷功能的细菌(?)seudomonas alcaligenes。这说明菌丝际解磷功能细菌利用了通过菌丝分泌的植物光合产物,参与了土壤难溶性有机磷的活化和周转；解磷细菌活化出的磷大部分被其自身所利用,与AM真菌形成对磷资源的竞争并进而抑制了AM真菌的生长,使解磷细菌对植株磷养分的贡献没有达到显著水平。3、供应不同形态磷酸盐显著改变菌丝际细菌群落结构。以韭葱为宿主时F. mosseae菌丝际的细菌群落结构组成,在不同施磷处理之间存在显著差异。与不施磷处理相比,无机磷处理增加了厚壁菌门(Firmicutes)的相对丰度,对蓝藻门(Cyanobacteria)则没有影响,而有机磷的施入反而降低了厚壁菌门(Firmicutes)的相对丰度,增加了蓝藻门(Cyanobacteria)的相对丰度。然而,蒺藜苜蓿和黑麦草为宿主植物时,菌丝际细菌的群落结构组成并没有受到磷形态的影响。这一结果说明宿主植物与磷形态在F. mosseae的生长和分泌物的数量方面存在交互作用。4、宿主植物种类对菌丝际细菌群落结构组成没有显著影响。接种Funneliformis mosseae时,菌丝际细菌群落结构组成显著不同于非菌丝际土壤的；以韭葱、蒺藜苜蓿、黑麦草三种植物为宿主的菌丝际细菌群落结构组成却很相似。说明菌丝际细菌群落的结构组成直接受到AM真菌根外菌丝分泌物的影响,宿主植物种类可能并不改变菌丝分泌物的成分。更多还原

【Abstract】 Arbuscular mycorrhizal (AM) fungi and bacteria are significant functional groups in the soil microflora, and their interactions play an important role in the soil phosphorus cycle. Interactions between AM fungi and bacteria are beneficial for soil P turnover and enhance P availability to plants. However, the underlying mechanisms by which these associations influence soil phosphorus turnover, and their ecological function, are not very well understood. In the present study, the interaction of two functional microorganisms (AM fungi and phosphate solubilizing bacteria) and its effects on organic phosphorus mineralization and turnover were studied using a compartmented cultivation system and molecular microbial ecology techniques (T-RFLP,13C-DNA-SIP,454high-throughput sequencing) at both physiological and molecular levels. The main results are listed below point by point:1. Ammonium-induced acidification in the presence of AM fungal hyphae in the hyphosphere improved maize uptake of P from phytin. NH4+treatment in the combined presence of phytin and AM fungal mycelium led to a decrease in hyphosphere pH, enhanced phosphatase activity in the hyphosphere and accelerated mineralization of phytin compared to the NO3-treatment, and improved maize uptake of P from phytin.2. Phosphate solubilizing bacteria (PSB) are involved in the mineralization and turnover of phytate in the hyphosphere, and these organisms assimilated carbon from13C-labeled maize. Co-inoculation of AM fungi and PSB into the hyphosphere chamber caused a marked decline in organic P concentration and an increase in microbial biomass phosphorus concentration in hyphosphere soil, compared to inoculation with AM fungi or PSB alone. The dual inoculation did not contribute to P uptake for maize, and hyphal growth of AM fungi was significantly inhibited under these conditions. Comparison between T-RFLP fingerprints and clone library indicated that Oxalobacteraceae, Streptomycetaceae and Pseudomonadaceae (including the inoculated PSB Pseudomonas alcaligenes strain) were labeled with13C derived from maize assimilates. These results suggest that PSB can utilize the photosynthate from plants via the mycelia of AM fungi, and are involved in soil organic phosphorus mineralization and turnover. The results suggest that PSB competed for available P with the AM hyphae in the hyphosphere, and that mycelial growth was suppressed because phytin was mineralized by PSB primarily for direct assimilation, and not for uptake by AMF and consequent promotion of both mycelial and plant growth..3. The composition of the bacterial community associated with extraradical Funneliformis mossaea mycelia was significantly changed by different forms of phosphorus supplied in the hyphosphere.16S T-RFLP analysis combined with NPMANOVA showed that different phosphorus forms significantly affected the bacterial community in the leek hyphosphere. The predominant phyla in those communities were Firmicutes and Cyanobacteria, as determined by454sequencing. Inorganic P treatment increased the relative abundance of Firmicutes, compared with the control with no added P, but no difference was seen for Cyanobacteria. However, the relative abundances of Firmicutes and Cyanobacteria were respectively decreased and increased after organic P supplementation. The bacterial community composition in the hyphospheres of Medicago truncatula and Lolium rigidum were not affected by the P forms. The results indicated the interactive effects of host plant and P form in determining F. mosseae growth and quantity of hyphal exudates.4. The bacterial community composition in the bulk soil was significantly different from that found in the F. mosseae hyphosphere. However, use of different plant species(Medicago truncatula, Allium porrum and Lolium rigidum) did not change the bacterial community composition associated with extraradical F. mosseae mycelia. These results suggest that the bacterial community composition in the hyphosphere is directly affected by mycelial exudates, but that host plant species do not significantly influence the composition of these exudates.更多还原