对虾生长不同阶段虾塘水体细菌和古菌的动态特征

The dynamics of bacteria and archaea in pond water associated with different growth phases of Penaeus vannamei

微生物是对虾养殖生态系统中的重要角色,与对虾的健康和品质息息相关。本研究利用荧光定量PCR和Miseq高通量测序手段对南美白对虾生长不同阶段(初期/5月、中期/6—7月、末期/8月)虾塘水体细菌和古菌的丰度、多样性及群落结构进行了调查,并分析了其对水质变化的响应。结果表明:随着投喂量的增加,水体碳和营养盐(氮、磷、硅)逐渐累积,铵氮含量在7、8月达到8.17 mg·L^-1,水体溶氧2.92 mg·L^-1,pH下降到6.66,氧化还原电位ORP低至29.10 mV;细菌丰度(1.67×10^8~3.91×10^9 copies·mL^-1)较古菌(3.08×10^5~2.77×10^7 copies·mL^-1)高出两个数量级,二者在5—7月相对平稳,8月显著增加(ANOVA test,P<0.05);Pearson相关分析显示,细菌和古菌丰度与营养盐水平呈显著正相关(P<0.05);养殖过程中微生物群落结构发生了明显演替,红杆菌科(Rhodobacteraceae)始终占优势(平均占比为27.93%),黄杆菌科(Flavobacteriaceae)、微杆菌科(Microbacteriaceae)和放线菌未定科(Actinomycetales)在养殖中期比例较高,腐败螺旋菌科(Saprospiraceae)比例先降低后升高,而肠球菌科(Enterococcaceae)比例在7、8月明显降低,从初期的5.61%降低到约1%;DHVEG-6是最优势的古菌类群(总体平均67.17%),其比例在养殖后期甚至达到90%,氨氧化古菌Candidatus Nitrosopumilus比例在养殖后期迅速下降,从5月的29%下降到8月的4.5%;水体细菌和古菌协同作用,共同维持虾塘微生态平衡。研究结果可为虾塘高密度养殖的举措优化、疾病防控及产量保障提供理论依据。

Microorganisms play an important role in the shrimp aquaculture ecosystem and are closely related to the health and quality of shrimp.Little is known about the dynamics of bacterial and archaeal community in the pond water associated with different growth phases of Penaeus vannamei.In this study,we examined the abundance,diversity and community structure of bacteria and archaea in the initial(May),middle(June-July),and late phase(August)using real-time fluorescence quantitative PCR(qPCR)and Illumina Miseq high-throughput sequencing.The responses of bacterial and archaeal community to environmental factors were analyzed.Carbon and nutrients(N,P,Si)concentrations in the water increased with increasing food consumption.NH4+concentration rose up to 8.17 mg·L^-1 in the mid-late phase,while the dissolved oxygen(DO),pH and the redox potential(ORP)decreased to 2.92 mg·L^-1,6.66 and 29.10 mV,respectively.The abundance of bacteria(1.67×10^8-3.91×10^9 copies·mL^-1)was two orders of magnitude higher than that of archaea(3.08×10^5-2.77×10^7 copies·mL^-1),and both of them were stable from May to July,but significantly higher in August(ANOVA test,P<0.05).The abundance of both bacteria and archaea positively correlated with nutrient levels(P<0.05).Bacterial and archaeal community compositions shift obviously during the growth cycle.Rhodobacteraceae always dominated in bacteria(on average 27.93%).Flavobacteriaceae,Microbacteriaceae,and Actinomycetales had higher relative abundances in the middle phase.The proportion of Saprospiraceae descended first and then increased during the whole cycle,while that of Enterococcaceae decreased from 5.61%in the initial phase to about 1%in the late phase.DHVEG-6 was the most dominant group of archaea(on average 67.17%),the relative abundance of which rose up to 90%in August.The proportion of ammonia-oxidizing archaea Candidatus Nitrosopumilus dropped rapidly in the late phase from 29%in May to 4.5%in August.In short,water bacteria and archaea cooperate to maintain the ecological balance of shrimp ponds.Our results can provide a theoretical basis for technology optimization,disease prevention,and yield guarantee of intensive shrimp aquaculture.