两种浮萍根系分泌物对荧光假单胞菌脱氮影响的差异及其剂量效应研究

本研究对太湖地区高效除氮紫背浮萍Spirodela polyrrhiza(HZ1)和低效除氮青萍Lemna minor(WX3)的根系分泌物进行了连续收集和分离,并考察了根系分泌物剂量与成分对反硝化细菌荧光假单胞菌Pseudomonas fluorescens脱氮效率的影响。结果发现,两种浮萍根系分泌物总组分均能显著促进P.fluorescens的脱氮效率,但对P.fluorescens的生长无影响。HZ1根系分泌物总组分(HO)促进作用显著高于WX3根系分泌物总组分(WO),这与HZ1对水体的除氮效率高于WX3的结果一致。两种浮萍根系分泌物各组分也有不同的效果,其中仅WX3根系分泌物酸性组分(WA)显著抑制了P.fluorescens的脱氮效率,HZ1根系分泌物不同组分是促进或无作用。总体上,P.fluorescens的脱氮效率随浮萍根系分泌物及其各组分添加剂量的增加呈先上升后下降的趋势,而WA组分先下降后基本不变,各组分在剂量为1.0%(v/v)时起最大效果。总之,根系分泌物与浮萍–微生物耦合系统的除氮效率密切相关,酸性组分是两种浮萍根系分泌物促进P.fluorescens脱氮效果差异的主要原因。

Different Effect of Root Exudates of Two Duckweed Species on Nitrogen Removal of Pseudomonas fluorescens and Their Dose-relationships

In this study, the root exudates of nitrogen-removal efficient Spirodela polyrrhiza(HZ1) and nitrogen-removal inefficient Lemna minor (WX3) from Tai Lake region were collected continuously and separated, and the effects of dose and composition of root exudates on the nitrogen removal efficiency of the denitrifying bacterium Pseudomonas fluorescens were also investigated. The results showed that the nitrogen removal efficiency of P. fluorescens was significantly stimulated by the crude root exudates of two duckweed species, which exhibited no effect on the growth of the P. fluorescens. The stimulation of the crude root exudates of HZ1 (HO) was significantly higher than that of WX3 (WO), which was consistent with the earlier research that the nitrogen removal abilities of HZ1 was higher than WX3 in treating the polluted water. An effect of different fractions of two duckweed root exudates was also observed. Among these fractions, only the acidic fraction of root exudates of WX3 (WA) inhibited the nitrogen removal efficiency of P. fluorescens, while all the fractions of root exudates of HZ1 displayed a stimulatory effect or no effect. Overall, the nitrogen removal efficiency of P. fluorescens firstly increased and then decreased with doses of duckweed root exudates and their fractions increase, with the exception of WA, where the efficiency remained unchanged after the initial decrease. When the dose was 1.0% (v/v), all of the fractions had the maximum effect. Therefore, these results indicated a close relationship between the root exudates and the nitrogen removal abilities of coupled duckweed-microbe systems, and the acidic faction was mainly responsible for the different effects of root exudates from two duckweed species on the nitrogen removal efficiency of P. fluorescens.