典型农田根际土壤伯克霍尔德氏菌群落结构及其多样性

Community Structure of Burkholderiales and Its Diversity in Typical Maize Rhizosphere Soil

在根际环境中伯克霍尔德氏菌(Burkholderiales)是一类重要的植物促生菌,其群落结构变化可能会影响植物的生长和发育。本研究针对伯克霍尔德氏菌目,采用特异性引物16S rRNA基因高通量测序技术,研究了田间条件下黑土、潮土和红壤中玉米根际伯克霍尔德氏菌群落结构及其对地上部作物生物量和产量的可能影响。结果表明:在三种土壤类型中,与未施肥相比,施肥对伯克霍尔德氏菌目的丰富度和多样性均没有显著影响。在伯克霍尔德氏菌的科水平主要检测到三类细菌,分别为草酸杆菌科(Oxalobacteraceae)、丛毛单胞菌科(Comamonadaceae)和伯克氏菌科(Burkholderiaceae),且草酸杆菌科是其中的优势菌。此外,施肥显著增加了有机质含量较低的潮土中马赛菌(Massilia spp.和Massilia sp.WG5)和伯克氏菌(Burkholderiaspp.)的相对丰度(P<0.05);增加了酸性红壤中草螺旋菌(Herbaspirillumsp.ZM319)的相对丰度,但降低了Noviherbaspirillum spp.的相对丰度(P<0.05);而在有机质含量最高的黑土中,所有检测到的伯克霍尔德氏菌均无明显地变化。进一步分析表明,土壤有效磷、速效钾含量和土壤pH是影响这几类细菌的主要因素,而马赛菌群落的变化可能会影响玉米地上部生物量和产量。本研究表明,尽管化学施肥是影响玉米地上部生物量和产量的主要原因,但是伯克霍尔德氏菌等根际微生物群落也可能是影响它们的潜在生物因素。

【Objective】Under the classβ-proteobacteria,Burkholderiales is a kind of Gram-negative bacteria,characterized physiologically as strict aerobic,facultative anaerobic and obligate anaerobic chemoheterotrophic types,and composed mainly of Burkholaceae,Oxalobacteriaceae,Alcaligenaceae,and Comamonadaceae in taxonomy.In rhizospheric environment,Burkholderiales is an important group of pro-growth bacteria that can promote growth and development of plants.It can not only promote plant growth by producing phytohormones,but also improve the environment in which plants grow via nitrogen fixation,nodulation and phosphorus solubilization.Studies,so far accomplished,have demonstrated that soil physicochemical properties,soil pH,soil type and fertilization can affect the community structure and composition of Burkholderiales,but failed to address variation of the effects with soil type and its potential relationship with crop yield.【Method】In this study,16S rRNA high-throughput sequencing of Burkholderiales was performed with a pair of specific primers.Based on the findings,responses of Burkholderiales to nitrogen,phosphorus and potassium fertilization(N,P and K)in community structure and of the maize crops in three different types of agricultural soils(phaeozem,cambisol and acrisol)in shoot biomass and yield were investigated.【Result】Results show that application of chemical fertilizer did not affect much richness and diversity of the Burkholderiales in the three types of soil,as compared to the unfertilized plot.Moreover,three taxa of bacteria,i.e.Oxalobacteraceae,Comammonadaceae,and Burkholderiaceae,were detected at the family level of Burkholderiales.And Oxalobacteraceae was the dominant group.In addition,fertilization markedly increased relative abundance of the Burkholderia(mainly Burkholderia spp.)and Massilia(mainly Massilia spp.and Massilia sp.WG5)in the cambisol low in organic matter(P<0.01),while it significantly increased relative abundance of the Herbaspirillum(mainly Herbaspirillum sp.ZM319),but decreased that of the Noviherbaspirillum(mainly Noviherbaspirillum spp.)(P<0.01)in acidic acrisol.However,it did not affect much the relative abundance of all detected groups of Burkholderiales in the phaeozem high in soil organic matter and nutrient.Pearson correlation analysis and canonical correspondence analysis(CCA)indicates that nutrient(such as AP and AK)content and soil pH are the main factors affecting the community composition and structure of these bacteria(Burkholderia,Massilia,Herbaspirillum and Noviherbaspirillum).Furthermore,linear regression analysis and Mantel test shows that only the relative abundance of Massilia is significantly correlated with the shoot biomass and yield of maize(P<0.05).All these statistical analyses demonstrate that changes in community structure of Massilia may affect shoot biomass and yield of the crop.【Conclusion】This study indicates that although chemical fertilization is the main cause of the increase in shoot biomass and yield of maize,changes in community structure of rhizosphere microbes,such as Burkholderiales,may also be potential biological factors affecting shoot biomass and yield of maize.