热带山地雨林木本豆科和樟科植物叶内生细菌群落:物种与功能群多样性及驱动因子

Foliar endophytic bacterial communities of woody Fabaceae and Lauraceae plants in tropical mountain rainforests:Understanding species and functional diversity and their driving factors

揭示热带木本豆科与樟科植物的叶内生细菌群落的物种与代谢功能群组成差异及其驱动因子有助于理解热带森林的植物适应性和生物多样性维持机制。本研究采用IlluminaMiseq测序平台检测海南尖峰岭热带山地雨林中豆科与樟科植物叶内生细菌,并采用FAPROTAX微生物地球化学循环代谢功能数据库注解内生细菌功能。从豆科植物的长脐红豆(Ormosia balansae)、软荚红豆(O.semicastrata)与樟科植物的厚壳桂(Cryptocarya chinensis)、硬壳桂(C.chingii)共4种植物检测到叶内生细菌可操作分类单元(operationaltaxonomicunits,OTUs)达1,123个,隶属于21门36纲51目92科160属,其中有600个OTUs被鉴定为变形菌门,72个OTUs为酸杆菌门,分别占总细菌序列数的57.17%和15.12%;噬纤维菌目的薄层菌属(Hymenobacter)及根瘤菌目的甲基杆菌属(Methylobacterium)的细菌物种最丰富,分别达37和27个OTUs。叶内生细菌物种组成在豆科与樟科植物之间存在显著差异(ANOSIM:R=0.5792,P=0.004)。基于群落非参数性检验的环境向量拟合分析(environmental vector fitting,Envfit)结果表明,对叶内生细菌群落物种组成影响最大的是叶全钾含量(leafpotassiumcontent,LKC)与比叶面积(specificleaf area,SLA)。有明确分类信息且功能已注释的叶内生细菌OTUs占总OTU数的54.63%,涉及28类代谢功能群,其中固氮功能群、好氧化能异养功能群、纤维素分解功能群、甲醇氧化功能群、甲烷氧化功能群、尿素分解功能群等6类功能群的相对多度在非豆科的厚壳桂属(Cryptocarya)显著高于豆科的红豆属(Ormosia)植物。非度量多维尺度分析(non-metricmultidimensional scaling,NMDS)结果表明,细菌代谢功能群主要受SLA和叶全磷含量(leaf phosphorus content,LPC)影响。尖峰岭热带山地雨林非豆科植物叶内生细菌群落中相对多度较高的碳、氮代谢功能群可能是其对低有效养分的土壤环境的适应性机制之一。

Aims:Revealing the differences in species and metabolic functional groups of endophytic bacterial communities between tropical woody Fabaceae and Lauraceae plants,as well as their driving factors,contributes to understanding the adaptation and biodiversity maintenance mechanisms of tropical forests.Method:In this study,Illumina Miseq sequencing platform was used to detect endophytic bacteria in Fabaceae and Lauraceae plants in the tropical mountain rainforest of Jianfengling in Hainan,and the FAPROTAX microbial geochemical cycle metabolic functional database was used to annotate the endophytic bacterial function.Results:A total of 1,123 operational taxonomic units(OTUs)of endophytic bacteria belonging to 21 phyla,36 classes,51 orders,92 families,and 160 genera were detected from four plant species,including two species(Ormosia semicastrata,O.balansae)of Fabaceae and two species(Cryptocarya chinensis,C.chingii)of Lauraceae.Among them,600 OTUs were Proteobacteria,accounting for 57.17%of the total bacterial sequences,and 72 OTUs were Acidobacteria,accounting for 15.12%.The bacterial species of the Hymenobacter of Cytophagales,and Methylobacterium of Rhizobiales were the most abundant,with 37 and 27 OTUs,respectively.There were significant differences in endophytic bacterial species composition between Fabaceae and Lauraceae plants(ANOSIM:R=0.5792,P=0.004).The results of the environmental vector fitting analysis based on community non-parametric tests showed that the leaf potassium content and specific leaf area had the greatest impact on the species composition of endophytic bacterial communities.Endophytic bacteria with clear classification information,accounting for 54.63%total number of bacterial OTUs,were annotated to 28 metabolic functional groups.Of these functional groups,nitrogen fixation,aerobic chemoheterotrophy,cellulose degradation,methanol oxidation,methane oxidation,and urea degradation showed significantly higher relative abundance in non-legume Cryptocarya plants than in legume Ormosia plants.The results of non-metric multidimensional scaling analysis showed that bacterial metabolic functional groups were mainly influenced by specific leaf area and leaf phosphorus content.Conclusion:The higher relative abundance of carbon and nitrogen metabolism functional groups in endophytic bacterial communities of non-legume plants in the Jianfengling tropical mountain rainforest may be one of their adaptive mechanisms to low effective nutrient soil environments.