云南热泉中氨氧化古菌的accA基因与amoA基因丰度与环境因子NO_2^-和NO_3^-的相关性

Abundances of ammonia-oxidizing archaeal accA and amoA genes in response to NO_2^- and NO_3^- of hot springs in Yunnan province

【目的】氨氧化古菌(ammonia-oxidizing archaea,AOA)可能通过近期刚发现的3-羟基丙酸盐/4-羟基丁酸盐途径(3-hydroxypropionate/4-hydroxybutyrate cycle,HP/HB)来固定CO2,在海洋和土壤环境下进行化能自养型生长。云南热泉系统已被证明具有丰富的AOA多样性。本论文旨在调查云南不同热泉中,这种CO2固定途径的关健酶——乙酰辅酶A羧化酶基因acc A和古菌氨单加氧酶基因amo A,及原核微生物16S rRNA基因的丰度变化,以及它们与环境因子的相关性。【方法】选择20处代表性热泉沉积物样品,通过荧光定量PCR技术,获得各目的基因丰度;利用R软件包对各样点地化参数进行主成分分析(Principal Component Analysis,PCA),并通过Mantel test检验各目的基因和地化参数间的相关性。【结果】细菌和古菌16S rRNA基因的丰度范围分别在6.6×107至4.19×1011和1.27×106至1.51×1011拷贝/g沉积物;古菌acc A和amo A基因的丰度范围为8.89×103至6.49×105和7.64×103至4.36×105拷贝/g沉积物,Mantel test结果显示acc A和amo A基因丰度间具有极显著的相关性(R=0.98,P<0.001),两者又分别都与热泉内的NO2-和NO3-浓度存在显著相关,与p H值等其它环境因子没有明显统计学意义上的相关性。【结论】云南地区热泉间的细菌和古菌丰度,以及两者比例关系都存在较大差异;相关性的统计结果进一步证明了热泉环境下的氨氧化古菌是通过HP/HB途径进行CO2固定;本次研究并未发现氨氧化古菌的丰度与环境p H存在明显统计学意义上的相关性,这与常温土壤环境的相关研究结果存在不同。

[ Objective ] Yunnan hot springs have highly diverseammonia-oxidizing archaea （ AOA）, which are autotrophic and can fix CO2 using the 3-hydroxypropionate/4-hydroxybutyrate （HP/HD） pathway. In this study, we investigated the abundances of prokaryotic 16S rRNA gene and archaeal accA and amoA genes in the sediments of hot springs of Yunnan Province, and analysed the correlations between the above gene abundances and environmental factors. [ Methods] We selectedthe sediments of twenty representative hot springs, anddetected the gene abundances by quantitative polymerase chain reaction （qPCR）. The principal component analysis （PCA） and the Mantel test in the R software package were performed for the correlations of gene abundance and environmental variables. [ Results] The bacterial and archaeal 16S rRNA gene abundances were from 6.6 × 10^7 to 4. 19 × 10^11 and from 1.27 × 10^6 to 1. 51 ×10^11 copies/g sediment, respectively; Archaeal accA and amoA genes were from 8.89 × 10^to3 6. 49 × 10^5 and from 7. 64 × 10^3to 4. 36 × 10^5 copies /g sediment, respectively. The results of mantel test showed that accA gene was significantly （ R = 0.98, P 〈 0. 001 ） correlated with amoA gene; Both of them also were correlated significantly with NO2^ - and NO3^ - , but not with pH. [ Conclusion] The abundances of bacterial and archaeal 16S rRNA genes and the ratio between them varied significantly among Yunnan hot springs. The archaealaccA and amoA genes showed significant correlation with each other, validating our previous finding that AOA in terrestrial hot springs might acquire energy from ammonia oxidation coupled with CO2 fixation using the 3-hydroxypropionate/4-hydroxybutyrate pathway.