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Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO硝酸盐型甲烷厌氧氧化(AOM)是控制稻田甲烷排放的一种新途径,大气CO

Currently, the influence of elevated atmospheric CO

Nitrite-dependent anaerobic methane oxidation (n-damo), catalyzed by bacteria closely related to Candidatus Methylomirabilis oxyfera, links the global carbon and nitrogen cycles. Currently, the contribution of n-damo in controlling methane emissions and nitrogen removal, and the key regulatory factors of this process in Chinese paddy fields are poorly known. Here, soil samples from 20 paddy fields located in different climate zones across China were collected to examine the n-damo activity and bacterial communities. The n-damo activity and bacterial abundance varied from 1.05 to 5.97 nmol CH

Paddy fields are one of the most important methane sources, which have great impacts on climate change. The nitrite-dependent anaerobic methane oxidation, by NC10 phylum bacteria-稻田是温室气体甲烷的重要排放源之一,对全球气候变化具有重要影响。由隶属于NC10门的

Candidatus Methanoperedens-like archaea, which can use multiple electron acceptors (nitrate, iron, manganese, and sulfate) for anaerobic methane oxidation, could play an important role in reducing methane emissions from freshwater wetlands. Currently, very little is known about the distribution and community composition of Methanoperedens-like archaea in freshwater wetlands, particularly based on their alpha subunit of methyl-coenzyme M reductase (mcrA) genes. Here, the community composition, diversity, and abundance of Methanoperedens-like archaea were investigated in a freshwater wetland through high-throughput sequencing and quantitative PCR on their mcrA genes. A large number of Methanoperedens-like mcrA gene sequences (119,250) were recovered, and a total of 31 operational taxonomic units (OTUs) were generated based on 95% sequence similarity cut-off. The majority of Methanoperedens-like sequences can be grouped into three distinct clusters that were closely associated with the known Methanoperedens species which can couple anaerobic methane oxidation to nitrate or iron reduction. The community composition of Methanoperedens-like archaea differed significantly among different sampling sites, and their mcrA gene abundance was 1.49 × 10

Nitrite-dependent anaerobic methane oxidation (n-damo) catalyzed by Candidatus Methylomirabilis oxyfera (M. oxyfera)-like bacteria is a new pathway for the regulation of methane emissions from paddy fields. Elevated atmospheric CO

The elevated atmospheric CO

Nitrite (NO2−)- and nitrate (NO3−)-dependent anaerobic oxidation of methane (AOM) are two new additions in microbial methane cycle, which potentially act as important methane sinks in freshwater aquatic systems. Here, we investigated spatial variations of community composition, abundance and potential activity of NO2−- and NO3−-dependent anaerobic methanotrophs in the sediment of Jiulonghu Reservoir (Zhejiang Province, China), a freshwater reservoir having a gradient of increasing nitrogen loading from upstream to downstream regions. High-throughput sequencing of total bacterial and archaeal 16S rRNA genes showed the cooccurrence of Candidatus Methylomirabilis oxyfera (M. oxyfera)-like and Candidatus Methanoperedens nitroreducens (M. nitroreducens)-like anaerobic methanotrophs in the examined reservoir sediments. The community structures of these methanotrophs differed substantially between the sediments of upstream and downstream regions. Quantitative PCR suggested higher M. oxyfera-like bacterial abundance in the downstream (8.6 × 107 to 2.8 × 108 copies g−1 dry sediment) than upstream sediments (2.4 × 107 to 3.5 × 107 copies g−1 dry sediment), but there was no obvious difference in M. nitroreducens-like archaeal abundance between these sediments (3.7 × 105 to 4.8 × 105 copies g−1 dry sediment). The 13CH4 tracer experiments suggested the occurrence of NO2−- and NO3−-dependent AOM activities, and their rates were 4.7–14.1 and 0.8–2.6 nmol CO2 g−1 (dry sediment) d−1, respectively. Further, the rates of NO2−-dependent AOM in downstream sediment were significantly higher than those in upstream sediment. The NO3− concentration was the key factor affecting the spatial variations of abundance and activity of NO2−-dependent anaerobic methanotrophs. Overall, our results showed different responses of NO2−- and NO3−-dependent anaerobic methanotrophs to increasing nitrogen loading in a freshwater reservoir.

Coastal wetlands are critical in the global carbon budget while vulnerable to plant invasion. Spartina alterniflora (S. alterniflora), a typical invasive plant species, has rapidly expanded in China’s coastal area since 1979, which disturbed the carbon cycle of the coastal wetland ecosystems. However, until now, the effect and underlying mechanisms of S. alterniflora invasion on methanotrophs are poorly known in coastal wetlands. Here, a large-scale investigation of the activity, abundance and community structure of methanotrophs was conducted in seven wetlands under both native (dominated by Phragmites australis, Kandelia candel or Avicennia marina) and invasive plants (dominated by S. alterniflora) across the southeast coast of China. Compared with the native community, S. alterniflora invasion led to a significant (p

The elevated atmospheric CO2 concentration (eCO2) has a great impact on soil microbial communities and their functions; however, how the activity and communities of methanotrophs respond to eCO2 in paddy ecosystem is poorly known. Here, we examined the effects of a 4-year exposure to eCO2 (EC; ambient + 200 ppm) in open top chambers on the potential activity, abundance and community composition of methanotrophs in paddy fields in Nanjing City, China. The potential activity was measured in a slurry incubation under aerobic condition, and the community composition and abundance of methanotrophs were analyzed through Illumina Miseq sequencing and quantitative PCR of pmoA genes. The results demonstrated that EC significantly increased (p

Nitrite-dependent anaerobic methane oxidation (n-damo) catalyzed by Candidatus Methylomirabilis oxyfera (M. oxyfera)-like bacteria is a new pathway for the regulation of methane emissions from paddy fields. Elevated atmospheric CO2 concentrations (e[CO2]) can indirectly affect the structure and function of microbial communities. However, the response of M. oxyfera-like bacteria to e[CO2] is currently unknown. Here, we investigated the effect of e[CO2] (ambient CO2 + 200 ppm) on community composition, abundance, and activity of M. oxyfera-like bacteria at different depths (0–5, 5–10, and 10–20 cm) in paddy fields across multiple rice growth stages (tillering, jointing, and flowering). High-throughput sequencing showed that e[CO2] had no significant effect on the community composition of M. oxyfera-like bacteria. However, quantitative PCR suggested that the 16S rRNA gene abundance of M. oxyfera-like bacteria increased significantly in soil under e[CO2], particularly at the tillering stage. Furthermore, 13CH4 tracer experiments showed potential n-damo activity of 0.31–8.91 nmol CO2 g−1 (dry soil) d−1. E[CO2] significantly stimulated n-damo activity, especially at the jointing and flowering stages. The n-damo activity and abundance of M. oxyfera-like bacteria increased by an average of 90.9% and 50.0%, respectively, under e[CO2]. Correlation analysis showed that the increase in soil dissolved organic carbon content caused by e[CO2] had significant effects on the activity and abundance of M. oxyfera-like bacteria. Overall, this study provides the first evidence for a positive response of M. oxyfera-like bacteria to e[CO2], which may help reduce methane emissions from paddy fields under future climate change conditions.

The elevated atmospheric CO2 concentration is well known to have an important effect on soil nutrient cycling. Ammonia oxidation, mediated by ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), is the rate-limiting step in soil nitrification, which controls the availability of two key soil nutrients (ammonium and nitrate) for crops. Until now, how the AOA and AOB communities in paddy soils respond to elevated CO2 remains largely unknown. Here, we examined the communities of AOA and AOB and nitrification potential at both surface (0–5 cm) and subsurface (5–10 cm) soil layers of paddy fields under three different CO2 treatments, including CK (ambient CO2 concentration), LT (CK + 160 ppm of CO2) and HT (CK + 200 ppm of CO2). The elevated CO2 was found to have a greater impact on the community structure of AOB than that of AOA in surface soils as revealed by high-throughput sequencing of their amoA genes. However, no obvious variation of AOA or AOB communities was observed in subsurface soils among different CO2 treatments. The abundance of AOA and AOB, and nitrification potential were significantly increased in surface soils under elevated CO2. The variation of AOB abundance correlated well with the variation of nitrification potential. The soil water content and dissolved organic carbon content had important impacts on the dynamic of AOB communities and nitrification potential. Overall, our results showed different responses of AOA and AOB communities to elevated CO2 in paddy ecosystems, and AOB were more sensitive to the rising CO2 concentration.

Nitrite-dependent anaerobic oxidation of methane (AOM), which is mediated by Candidatus Methylomirabilis oxyfera (M. oxyfera)-like bacteria, has the great potential to reduce methane emissions from paddy ecosystems. Fertilization, a necessary practice for increasing crop yields, could greatly affect nitrite-dependent AOM process. Here, we investigated the abundance, community composition and activity of M. oxyfera-like bacteria at different layers (0–10, 20–30 and 40–50 cm) of paddy soils under three fertilization treatments, including unfertilized control (CK), chemical fertilization (CF) and organic fertilization (OF). The 16S rRNA gene abundance of M. oxyfera-like bacteria in soils under CF (6.1 × 106–2.2 × 107 copies g−1 dry soil) and OF (8.9 × 106–1.8 × 107 copies g−1 dry soil) treatments was higher than that under CK treatment (5.0 × 106–1.5 × 107 copies g−1 dry soil). An obvious separation of M. oxyfera-like bacterial communities was observed between different fertilization treatments, and a higher diversity of these bacteria was detected in CF and OF soils. The nitrite-dependent AOM activity was increased in soils under CF (3.6–11.5 nmol CO2 g−1 (dry soil) d−1) and OF (3.4–7.2 nmol CO2 g−1 (dry soil) d−1) treatments as compared to CK (1.6–4.4 nmol CO2 g−1 (dry soil) d−1) treatment, particularly at the layer of 20–30 cm. Overall, our results demonstrated that the communities and activity of M. oxyfera-like bacteria responded positively to both chemical and organic fertilization, which expanded our knowledge of the role of nitrite-dependent AOM in regulating methane emissions from paddy ecosystems.

Candidatus Methanoperedens nitroreducens (M. nitroreducens)-like archaea, catalyzing anaerobic methane oxidation coupled with nitrate reduction, could play an important role in reducing methane emissions from paddy ecosystems. Currently, the spatial and temporal variations of the communities of M. nitroreducens-like archaea and the factors regulating their distribution in paddy soils are poorly known. Here, we examined the diversity, community composition and abundance of these anaerobic methanotrophs at four representative depths (0–10, 10–20, 20–30 and 30–40 cm) of paddy soils across four rice growth stages (tillering, jointing, flowering and milky stages). High-throughput sequencing of M. nitroreducens-like archaeal mcrA genes showed that their community structure varied among different depths. In contrast, the community structure of these archaea remained relatively stable across rice growth stages. Further, both soil depth and rice growth stage had a significant impact on the abundance of mcrA genes. The gene abundance varied from 7.6 × 105 to 5.0 × 106 copies g−1 dry soil with higher values in 20–30 cm soils, and the abundance was found to be decreased from tillering to milky stages. The soil organic carbon content and ammonium content were the key factors affecting the community structure of these archaea. Our results indicated that both soil depth and crop growth stage greatly affected the abundance of M. nitroreducens-like archaea, while their community structure seemed to be more responsive to soil depth. Taken together, both space and time scales should be considered for better understanding the role of M. nitroreducens-like archaea reducing methane emissions from paddy ecosystems.

Fertilization is a necessary practice for paddy fields to achieve high crop yields, and this practice could have an important impact on soil nitrogen cycle. Anammox (anaerobic ammonium oxidation) is an important process in the nitrogen cycle of paddy ecosystems. However, until now, the influence of nitrogen fertilization on anammox, is not well understood. Here, the vertical distribution of the activity, abundance and community composition of anammox bacteria was investigated in paddy soils (0–50 cm) under three different fertilizer treatments: chemical fertilizer (CF), organic fertilizer (OF) and unfertilized control (CK). The 15N tracer experiments confirmed anammox activity in different depths of paddy soils across all treatments, with the highest activity in the surface soil layer (0–10 cm) under OF treatment. The potential anammox rates were 0.76–1.82, 0.95–2.39 and 1.19–3.62 nmol N g−1 (dry soil) h−1, respectively, under CK, CF and OF treatments. The abundance of anammox bacterial hzsA genes in upper 30 cm layers was significantly higher under CF (3.1 × 106-6.5 × 106 copies g−1 dry soil) and OF (3.4 × 106-7.1 × 106 copies g−1 dry soil) treatments than CK treatment (2.1 × 106-3.5 × 106 copies g−1 dry soil). Similar community composition of anammox bacteria was observed in soils under different fertilizer treatments, with Candidatus Brocadia being the single dominant genus. Overall, our results demonstrated that the input of inorganic or organic fertilizers significantly increased the anammox bacterial abundance and activity in both surface and subsurface paddy soils, while the anammox community remained relatively stable.