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The discovery of denitrifying anaerobic methane oxidation with nitrite as electron acceptor mediated by ' C andidatus Methylomirabilis oxyfera' connected the biogeochemical carbon and nitrogen cycle in a new way. However, it is important to have a comprehensive understanding about the distribution of M . oxyfera-like bacteria in the terrestrial realm, especially the wetland ecosystems that are known as the largest natural source of atmospheric methane. Here, our molecular evidence demonstrated that a wide geographical distribution of M . oxyfera-like bacteria at oxic/anoxic interfaces of various wetlands ( n = 91) over the Chinese territory. Intriguingly, the M . oxyfera-like bacteria were detected in some extreme environments, indicating that M . oxyfera-like bacteria occupied a wide range of habitats. Quantitative polymerase chain reaction estimated that the abundance of M . oxyfera-like bacteria ranged from 2.2 × 103 to 2.3 × 107 copies g−1 dry soil, and up to around 0.62% of the total number of bacteria. Moreover, the M . oxyfera-like bacteria showed high biodiversity in wetland ecosystems based on the analysis of 462 pmoA and 287 16S rRNA gene sequences. The current study revealed the widespread distribution and biogeography of M . oxyfera-like bacteria in the terrestrial system. [ABSTRACT FROM AUTHOR]

Manure fertilizers are widely used in agriculture and highly impacted the soil microbial communities such as ammonia oxidizers. However, the knowledge on the communities of archaeal versus bacterial ammonia oxidizers in paddy soil affected by manure fertilization remains largely unknown, especially for a long-term influence. In present work, the impact of manure fertilization on the population of ammonia oxidizers, related potential nitrification rates (PNRs) and the key factors manipulating the impact were investigated through studying two composite soil cores (long-term fed with manure fertilization versus undisturbed). Moreover, soil incubated with NH4+ for 5 weeks was designed to verify the field research. The results showed that the copy numbers of bacterial amoA gene in the manure fed soil were significant higher than those in the unfed soil ( p < 0.05), suggesting a clear stimulating effect of long-term manure fertilization on the population of ammonia-oxidizing bacteria (AOB). The detected PNRs in the manure fed soil core (14-218 nmol L−1 N g−1 h−1) were significant higher than those in the unfed soil core (5-72 nmol L−1 N g−1 h−1; p < 0.05). Highly correlations between the PNRs and the bacterial amoA gene copies rather than archaeal amoA gene were observed, indicating strong nitrification capacity related to bacterial ammonia oxidizers. The NH4+-N significantly correlated to the abundance of AOB ( p < 0.01) and explained 96.1% of the environmental variation, showing the NH4+-N was the main factor impacting the population of AOB. The incubation experiment demonstrated a clear increase of the bacterial amoA gene abundance (2.0 × 106 to 8.4 × 106 g−1 d.w.s. and 1.6 × 104 to 4.8 × 105 g−1 d.w.s.) in both soil but not for the archaeal amoA gene, in agreement with the field observation. Overall, our results suggested that manure fertilization promoted the population size of bacterial ammonia oxidizers rather than their archaeal counterparts whether in long-term or short-term usage and the NH4+-N was the key impact factor. [ABSTRACT FROM AUTHOR]