Liu Lihui, Xu Xiurong, Cao Yangchun, Cai Chuanjiang, Cui Hongxiao, Yao Junhu
College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
AMB Express. 2017 Dec;7(1):76. doi: 10.1186/s13568-017-0377-2. Epub 2017 Apr 4.
Studies proved that addition of nitrate in rumen could lead to reduction of methane emission. The mechanism of this function was involved in the competition effect of nitrate on hydrogen consumption and the inhibitory effect of generated nitrite on methanogen proliferation. The present study investigated an alternative mechanism that denitrifying anaerobic methane oxidizing (DAMO) bacteria, DAMO archaea and anammox bacteria may co-exist in rumen, therefore, more methane can be oxidized when addition of nitrate. Ruminal batch culture model was used to test the effects of addition of 5 mM NaNO, 4 mM NHCl, or both into the culture substrate on methane production, fermentation patterns, and population of methanogens, NC10 and anaerobic methanotrophic-2d (ANME-2d). Our results showed that NC10 in the ruminal culture was detected by polymerase chain reaction (PCR) when using NC10 special primer sets, and addition of nitrate reduced methane production and the relative proportions of methanogen, whereas increased the relative proportion of NC10. A combined addition of ammonia salt and nitrate did not show further inhibitory effect on methane production but accelerated nitrate removal. We did not detect DAMO archaea in ruminal culture by real-time PCR when using ANME-2d special primer sets. The present study may encourage researchers to pay more attention to methane oxidation performed by anaerobic methanotroph when studying the strategies of inhibiting ruminal methane emission.
研究证明，在瘤胃中添加硝酸盐可导致甲烷排放减少。该功能的机制涉及硝酸盐对氢气消耗的竞争效应以及生成的亚硝酸盐对产甲烷菌增殖的抑制作用。本研究探讨了一种替代机制，即反硝化厌氧甲烷氧化（DAMO）细菌、DAMO古菌和厌氧氨氧化细菌可能在瘤胃中共存，因此，添加硝酸盐时更多的甲烷可被氧化。采用瘤胃批次培养模型来测试向培养底物中添加5 mM NaNO₃、4 mM NH₄Cl或两者对甲烷产生、发酵模式以及产甲烷菌、NC10和厌氧甲烷营养型-2d（ANME-2d）数量的影响。我们的结果表明，当使用NC10特异性引物对时，通过聚合酶链反应（PCR）在瘤胃培养物中检测到了NC10，添加硝酸盐可降低甲烷产量和产甲烷菌的相对比例，而增加了NC10的相对比例。氨盐和硝酸盐的联合添加对甲烷产生没有进一步的抑制作用，但加速了硝酸盐的去除。当使用ANME-2d特异性引物对时，我们通过实时PCR在瘤胃培养物中未检测到DAMO古菌。本研究可能会促使研究人员在研究抑制瘤胃甲烷排放的策略时，更多地关注厌氧甲烷营养菌进行的甲烷氧化作用。
