长江下游厌氧氨氧化细菌标记基因相对丰度及影响因素

为探索河流系统中厌氧氨氧化细菌的分布情况, 于2014年春秋两季采集长江下游6个断面的水体和沉积物样品, 通过宏基因组测序方法, 根据优化序列与自建厌氧氨氧化细菌标记基因hzsA, hzsB, hzsC, hdh数据集的比对结果, 计算各基因相对丰度。结果表明, 水体溶解氧浓度较高导致厌氧氨氧化细菌标记基因丰度极低, 而沉积物中各基因相对丰度较高, 平均值分别为4.540×10^-10, 4.939×10^-10, 4.333×10^-10和2.859×10^-10。随着温度升高, 秋季沉积物中各基因相对丰度显著高于春季。大通、南京和徐六泾沉积物中各基因相对丰度较高, 这与人类活动扰动的增强以及入海口盐度升高有关。物种分类鉴定结果表明, 长江下游沉积物中厌氧氨氧化细菌在属水平上以Candidatus Brocadia和Candidatus Jettenia为主。厌氧氨氧化细菌标记基因相对丰度与NO₂^--N,NO₃^--N和NH₄⁺-N等理化因子相关, 并且, 由于NO₂^--N浓度远远低于NH₄⁺-N, 因此NO₂^--N浓度是长江下游沉积物中厌氧氨氧化细菌生长的限制性因子。

Relative Abundance of Anammox Bacterial Marker Genes in theLower Yangtze River and Their Affecting Factors

In order to investigate the distribution of anammox bacteria in river ecosystems, water and sedimentsamples were collected at 6 sites along the lower Yangtze River in spring and autumn in 2014. Clean reads ofmetagenomic sequencing were BLAST against self-constructed datasets of anammox bacterial marker genes hzsA,hzsB, hzsC and hdh, and valid hits were used to calculate their relative abundances. As results, average relativeabundances of hzsA, hzsB, hzsC and hdh genes in water were extremely low due to the excess dissolved oxygenwhich was not suitable for anammox bacteria. Whereas, the average relative abundances in sediments were muchhigher, i.e., 4.540×10^-10, 4.939×10^-10, 4.333×10^-10 and 2.859×10^-10, respectively. Due to the temperature rise,average relative abundances of hzsA, hzsB, hzsC and hdh genes in sediment samples in autumn were higher thanthose in spring. From the changes alongside the river, average relative abundances of hzsA,hzsB,hzsCandhdhgenes at Datong, Nanjing and Xuliujing were relatively higher, which was due to anthropogenic activity andsalinity increase in the estuary. Based on the results of taxonomic identification, anammox bacteria in the lowerYangtze River mainly consisted of Candidatus Brocadia and Candidatus Jettenia at genus level. Relativeabundances of hzsA,hzsB,hzsCandhdhgenes were related to NO₂^--N, NO₃^--N and NH₄⁺-N concentration, ofwhich NO₂^--N concentration was the restrictive factor as it was much lower than NH₄⁺-N concentration.