富营养水体中2种水生植物的根际微生物群落特征

选取宁波市城区内河2个营养类型水体日湖(中-富营养类型)和卧彩江(重富营养类型),于2008年8~11月,利用MIDI Sherlock MIS系统和其他传统方法,跟踪监测了2个水体内2种常见水生净化植物粉绿狐尾藻(Myriophyllum aquaticum)、喜旱莲子草(Alternanthera philoxeroides)根际微生物的种类、数量及其季节变化,分析了水体主要水质参数、水体微生物与植物根际微生物之间的相关性.结果表明,水生植物根际效应显著,不同月份植物根际微生物数量均要显著高于水体环境;植物种类对植物根际微生物影响显著,在日湖水体,狐尾藻根际微生物数量要显著高于喜旱莲子草;在卧彩江,2种植物根际细菌数量无显著差异,放线菌、真菌数量差异显著,植物根际微生物数量与水体环境因子之间具有一定的相关性,调查期间,日湖水温、TN、TP、Chla与植物根际微生物数量间均无显著相关,仅COD与喜旱莲子草根际细菌数量显著负相关;在卧彩江,TP与粉绿狐尾藻、喜旱莲子草根际放线菌数量显著负相关,其余水质参数与根际微生物数量均无显著相关.植物根际优势菌种以假单胞菌属(Pseudomonas)、微球菌属(Micrococcus)、黄杆菌属(Chryseobacterium)、不动杆菌属(Acinetobacter)等有机物降解微生物为主,环境因素的变化和植物种类的不同也导致了葡萄球菌属(Staphylococcus),食酸菌属(Acidovorax)、节杆菌属(Arthrobacter)等特有菌种的出现.对植物根际微生物群落结构进行聚类分析表明,除日湖喜旱莲子草根际微生物群落结构在夏、秋两个季节相似性较高外,其余几个处理的根际微生物群落结构相似性在21.60%~51.57%.日湖植物根际微生物多样性夏季高于秋季,而卧彩江中夏季低于秋季;日湖中2种植物之间无论夏秋均无显著差异,而在卧彩江,夏季喜旱莲子草要显著高于粉绿狐尾藻,秋季则完全相反,据此说明植物根际微生物多样性受水体富营养化程度和植物种类等多重因素的影响.

Characteristics of rhizosphere microbial community structure of two aquatic plants in eutrophic waters

Rhizosphere microorganisms in Myriophyllum aquaticum and Alternanthera philoxeroides were identified and enumerated using Sherlock Microbial Identification System (Sherlock MIS), followed by correlation analyses with environmental factors in Lake Rihu (medium-eutrophic) and River Wocaijiang (high-eutrophic) in Ningbo from August to November 2008. Effects of plant rhizosphere on microbial community composition were significant. The abundance of microbes in the rhizosphere of macrophytes was significantly higher than that in the water column in each month. Community composition of rhizosphere microorganism differed significantly between plant species. In Lake Rihu, the number of microbes in the rhizosphere of M. aquaticum was significantly higher than that of A. philoxeroides. There was no significant difference between the abundances of bacteria in the rhizosphere of two plants, while the abundances of rhizosphere actinomyces and fungi differed significantly between two plant species in River Wocaijiang. Correlations between population size of rhizosphere microbe and environmental factors varied greatly among plant species or sampling sites. Abundance of microbes in the rhizosphere of A. philoxeroides was negatively correlated to chemical oxygen demand (COD), while there was no significant correlation with water temperature, total nitrogen (TN), total phosphate (TP) and Chl.a in Lake Rihu. The number of rhizosphere microbes showed a negative correlation with TP and no significant correlation with other environmental factors in River Wocaijiang. The dominant microbial genera in the rhizosphere of the two macrophytes were Pseudomonas, Micrococcus, Chryseobacterium, Acinetobacter etc. Some other specific functionalmicrobes, e.g. Staphylococcus, Acidovorax, Arthrobacter, were also found in the rhizospheres due to the heterogeneity of environmental conditions and plants. Cluster analyses using Primer 5.0 showed that the similarity of the community structure between summer and autumn was significantly higher than those between the rest seasons where similarities were more dynamic with the value of 21.60%~51.57% in the rhizosphere A. philoxeroides. Diversity of rhizosphere microorganisms was higher in summer than that in autumn in Lake Rihu. In contrast, rhizosphere microbiota was more diverse in autumn than in summer in River Wocaijiang. There was no significant difference of diversity of rhizosphere microbiota between two plants in Lake Rihu. In River Wocaijiang, the diversity of rhizosphere microorganisms of M. aquaticum was higher than that of A. philoxeroides in summer and with the opposite results in autumn. The results obtained in this study indicated that the rhizosphere microbial community structure was affected significantly by the environmental factors and plant species.