一株嗜松青霉JP-NJ4的解磷特性

【目的】土壤中磷素供应不足是造成马尾松林地力衰退的原因之一。本研究对前期从马尾松根际土样中分离筛选出的一株解磷能力较强的嗜松青霉JP-NJ4的解无机磷及解有机磷能力进行探讨。【方法】探究嗜松青霉JP-NJ4对4种无机磷源及2种有机磷源的降解能力,并对其分泌的有机酸和酶类进行测定,对其解磷特性进行初步分析。【结果】表明JP-NJ4菌株可在4种不同无机磷源的培养基中生长,其中对磷酸钙[Ca3(PO4)2]的解磷效果最好,对4种磷源的解磷能力大小为:磷酸钙磷酸铝磷酸氢钙磷酸铁;其分泌的有机酸种类主要为葡萄糖酸、草酸及丙二酸;JP-NJ4菌株的磷酸酶活性较高,并具有一定的植酸酶活性;同时对草甘膦具有较好的生物降解功能,降解率达49.6%。【结论】嗜松青霉JP-NJ4解磷能力受磷源的结构组成影响,且解磷能力与发酵液pH值呈负相关关系;该菌株分泌的葡萄糖酸和草酸对磷酸钙及磷酸铝的溶解效果较明显。本研究供试菌株嗜松青霉JP-NJ4具有良好的解磷功能,在作为林业生物菌肥方面具有极大的应用潜力。     

Nutrient enrichment increased species richness of leaf litter fungal assemblages in a tropical forest

Microbial communities play a major role in terrestrial ecosystem functioning, but the determinates of their diversity and functional interactions are not well known. In this study, we explored leaf litter fungal diversity in a diverse Panama lowland tropical forest in which a replicated factorial N, P, K and micronutrient fertilization experiment of 40 × 40 m plots had been ongoing for nine years. We extracted DNA from leaf litter samples and used fungal‐specific amplification and a 454 pyrosequencing approach to sequence two loci, the nuclear ribosomal internal transcribed spacer (ITS) region and the nuclear ribosomal large subunit (LSU) D1 region. Using a 95% sequence similarity threshold for ITS1 spacer recovered a total of 2523 OTUs, and the number of unique ITS1 OTUs per 0.5–1.0 g leaf litter sample ranged from 55 to 177. Ascomycota were the dominant phylum among the leaf litter fungi (71% of the OTUs), followed by Basidiomycota (26% of the OTUs). In contrast to our expectations based on temperate ecosystems, long‐term addition of nutrients increased, rather than decreased, species richness relative to controls. Effect of individual nutrients was more subtle and seen primarily as changes in community compositions especially at lower taxonomic levels, rather than as significant changes in species richness. For example, plots receiving P tended to show a greater similarity in community composition compared to the other nutrient treatments, the +PK, +NK and +NPK plots appeared to be more dominated by the Nectriaceae than other treatments, and indicator species for particular nutrient combinations were identified.     

分根培养系统中AM真菌抑制大豆胞囊线虫病的效应

在分根培养系统中将大豆(Glycine max Merrill)幼苗接种丛枝菌根(Arbuscular mycorrhiza,AM)真菌摩西球囊霉(Glomus mosseae)、幼套球囊霉(G.etunicatum)或/和大豆胞囊线虫(SCN,Heterodera glycines)后,定期测定大豆根系中AM真菌及线虫侵染率、病情指数、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)、β-1,3-葡聚糖酶及几丁质酶活性的动态变化。结果表明,将大豆胞囊线虫与AM真菌接种于分根培养系统同一室或分别接种于不同室,AM真菌均能显著降低大豆病情指数和线虫侵染速率,且将二者接种同一室处理的效果大于不同室处理;与只接种SCN的处理相比,接种摩西球囊霉和幼套球囊霉3周后在同室接种SCN处理的根围土壤中胞囊数、根上胞囊数和根内线虫数分别降低了47.4%、58.9%、46.6%和50.5%、67.0%、57.5%,表明AM真菌能显著抑制线虫的发育;摩西球囊霉和幼套球囊霉在一定时间段内诱导了大豆根系过氧化物酶、苯丙氨酸解氨酶、β-1,3-葡聚糖酶及几丁质酶的活性。摩西球囊霉和幼套球囊霉能够诱导大豆植株抵抗大豆胞囊线虫的侵染,既能在同一室的根围局部与SCN竞争侵染位点,又能对不同室的根系诱导产生防御性酶,推测摩西球囊霉和幼套球囊霉拮抗SCN的效应既是局部的,也是系统性的。     

Preconditioning of leaves by solar radiation and anoxia affects microbial colonisation and rate of leaf mass loss in an intermittent stream

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