NaCl胁迫对滨梅根际细菌群落多样性及优势菌群的影响

【目的】研究盐胁迫下耐盐植物根际微生物群落变化情况。【方法】基于温室盆栽试验,结合植株生长测定、土壤理化性质分析、PCR-DGGE图谱技术、香农多样性分析、主成分分析等方法,研究NaCl(0、2.9、8.8 g/L)溶液胁迫下,耐盐果树滨梅根际和非根际土壤细菌多样性变化情况及变化规律,以及滨梅生长及土壤理化性质变化。【结果】盐胁迫60 d后, 高浓度NaCl(8.8 g/L)溶液处理下滨梅根际土壤细菌16s rDNA序列变性梯度凝胶电泳(DGGE)图谱中的条带亮度、多样性指数、均匀度指数和丰富度指数最高, 非根际土壤中的条带数明显减少, 条带亮度变暗, 丰富度指数最低。对DGGE谱带进行聚类分析发现, 不同谱带间具有较高的相似性(>62%), 其中根际盐处理试验组和根际对照组可聚为一类, 非根际盐处理试验组可聚为一类, 非根际对照组单独聚为一类。选择9条主要优势条带克隆测序, 其中细菌类群为变形菌门、拟杆菌门、酸杆菌门和放线菌门。这些优势菌中除放线菌Candidatus属外,其他均对植物生长具有促进作用。对主要优势菌的变性梯度凝胶电泳(DGGE)图谱进行主成分(PCA)分析发现, 非根际细菌与根际细菌在第一主成分上完全分离, 非根际细菌均聚为一类, 而根际细菌则按亲缘关系聚类。【结论】在耐盐果树滨梅正常生长时,一定程度的盐胁迫不但未能对根际土壤微生物群落造成伤害, 反而起到一定的促进作用, 这种促进作用体现为植株根系对有益细菌生长的保护和促进, 以及对群落多样性的维持, 而非根际土壤细菌的生长和群落多样性则受到了较为严重的伤害。

Effect of NaCl stress on bacterial community diversity and core microbiome in rhizosphere and bulk soil of beach plum (Prunus maritima Marshall)

Objective] The environmental impacts of salinity are receiving increasing attention.However,the effects of soil salt concentrations on the structure and function of the soil microbial communities remain poorly understood.Method] In the present study,using plant growth measurement,soil physicochemical property analysis,PCR-DGGE technology,Shannon index and principle component analysis,a pot experiment was conducted to investigate the effects of salinity (i.e.,irrigation with 0,2.9,and 8.8 g/L NaCl solutions) on soil properties,the diversity of soil bacterial communities,and the growth of beach plum (Prunus maritima Marshall) cutting seedlings.Result] Neither sprout length or leaf area was significantly affected by the irrigation treatments,whereas the chlorophyll contents first increased then decreased with increasingly salt stress.The rhizosphere contained much more organic matter and total nitrogen than the bulk soil but possessed a significant lower pH.Furthermore,the cation exchange capacity of the rhizosphere soil increased significantly with increasing salinity,and the rhizosphere soil treated with 8.8 g/L NaCl yielded the greatest number of DGGE bands and band grayscales,as well as the highest diversity,richness and evenness indices.Meanwhile,the bulk soil yielded fewer bands and band grayscales,as well as lower diversity,richness and evenness indices.Cluster analysis revealed that the DGGE profiles from the same sampling site (rhizosphere or bulk) clustered together,except control from bulk soil.In addition,there were nine major bands,which were cloned,sequenced,and identified as members of the Proteobacteria,Bacteroidetes,Acidobacteria and Actinobacteria.Principal component analysis revealed consistent differences in the diversity patterns of the nine major rhizosphere taxa and those of the bulk soil,and the nine major rhizosphere taxa were clustered by genetic relationship.Conclusion] The results of the present study suggest that the salt stress-resistance of beach plum is at least partially mediated by its rhizosphere soil microbes,even though high salt concentrations stress the bacterial community of the bulk soil.