title: Nitrate decreases methane production also by increasing methane oxidation through stimulating NC10 population in ruminal culture.
abstract: 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 NaNO3, 4 mM NH4Cl, 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.
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Lihui
authors.initials: L
authors.lastname: Liu
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China. 244205036@qq.com.
authors.forename: Xiurong
authors.identifier: http://orcid.org/0000-0001-8395-793X
authors.initials: X
authors.lastname: Xu
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Yangchun
authors.initials: Y
authors.lastname: Cao
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Chuanjiang
authors.initials: C
authors.lastname: Cai
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Hongxiao
authors.initials: H
authors.lastname: Cui
authors.affiliation: College of Animal Science and Technology, Northwest A&F University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Junhu
authors.initials: J
authors.lastname: Yao
keywords: Ammonium salt; Denitrifying anaerobic methane oxidizing; NC10; Nitrate; Ruminal methane emission