过量氮输入对寡营养海水细菌群落代谢潜力的影响

细菌在海洋氮循环中起关键作用,而过量氮输入对细菌群落代谢潜力的影响还未被充分阐明.本研究通过构建3组寡营养海水生态微宇宙,包括对照组、一次性输入组(一次性输入硝酸盐使体系中硝氮浓度为1.0 mg·L-1)和连续性输入组(每隔2 d输入一次硝酸盐,使体系中硝氮浓度每次增加0.125 mg·L-1,直至与一次性输入组达到相同水平),利用Biolog-Eco板技术和16S rDNA PICRUSt(Phylogenetic investigation of communities by reconstruction of unobserved states)功能基因预测,研究过量氮输入下细菌群落代谢潜力的动态变化.结果表明,实验第16 d,氮的连续性输入提高了细菌群落的碳源利用能力,对照和连续性输入组中碳源利用特征随采样时间发生了显著变化.此外,预测到的功能基因家族组成随时间明显变化,并与亚硝酸盐、铵盐、磷酸盐、化学需氧量、溶解氧、pH和总磷密切相关,固氮、异化硝酸盐还原、反硝化、异化硝酸盐还原到铵和同化硝酸盐还原相关基因的相对丰度受到了氮输入的影响,而氮连续输入导致的氮代谢相关基因变化较一次性输入更为普遍.本研究初步揭示了过量氮输入对寡营养海水细菌群落代谢潜力的影响,为探明近岸海域过量氮输入的微生态效应提供了基础数据.

Effect of excess nitrogen loading on the metabolic potential of the bacterial community in oligotrophic coastal water

Bacteria play a key role in the marine nitrogen (N)cycle.However,the effect of excess N loading on metabolic potential of bacterial communities has not been fully elucidated. In this study, we constructed three groups of oligotrophic coastal water microcosms including the control, one-of floading (one-off loading of nitrate to 1.0 mg·L^-1 in the system) and periodic loading (once every two days, and the concentration of nitrate in the system increased by 0.125 mg·L^-1 until to the same level of nitrate as one-off loading group).Biolog-Eco plates and 16S rDNA PICRUSt (Phylogenetic investigation of communities by reconstruction of unobserved states) pipeline were used to investigate the dynamics in metabolic potential of bacterial communities under excess N loading. The results show that the periodic N loading promoted the carbon source utilization ability of bacterial communities at day 16 of the experiment. The utilization patterns of bacterial communities for six carbon sources were significantly affected by sampling time in control and periodic loading groups.In addition, the composition of predicted functional gene families showed temporal variation, which was significantly correlated with nitrite, ammonium, phosphate, chemical oxygen demand, dissolved oxygen, pH and total phosphorous. The relative abundances of genes relevant with N fixation, dissimilatory nitrate reduction, denitrification, dissimilatory nitrate reduction to ammonium and assimilatory nitrate reduction were significantly affected by N loading.The changes of the relative abundances of genes mediating N metabolism induced by periodic N loading were more extensive compared with one-off loading. This study preliminarily reveals the impact of excess N loading on the metabolic potential of bacterial community in the oligotrophic coastal water, and provided the basic data for evaluating the micro-ecological effects of excess N loading in coastal water.