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Net emissions of the potent GHG methane from ecosystems represent the balance between microbial methane production (methanogenesis) and oxidation (methanotrophy), each with different sensitivities to temperature. How this balance will be altered by long-term global warming, especially in freshwaters that are major methane sources, remains unknown. Here we show that the experimental warming of artificial ponds over 11 years drives a disproportionate increase in methanogenesis over methanotrophy that increases the warming potential of the gases they emit. The increased methane emissions far exceed temperature-based predictions, driven by shifts in the methanogen community under warming, while the methanotroph community was conserved. Our experimentally induced increase in methane emissions from artificial ponds is, in part, reflected globally as a disproportionate increase in the capacity of naturally warmer ecosystems to emit more methane. Our findings indicate that as Earth warms, natural ecosystems will emit disproportionately more methane in a positive feedback warming loop.Methane emissions are determined by the balance of microbial methane production relative to consumption. Warming drives larger increases in methane production than consumption in experimental ponds, suggesting that natural ecosystems may represent a positive feedback under climate change.

Surgery is the most important treatment for perianal abscesses. However, the gut microbiota of patients with perianal abscess and the effects of perianal abscess on the gut microbiota after surgery are unknown. In this study, significant changes in interleukin 6 and tumor necrosis factor-α in the blood of healthy subjects, patients with perianal abscesses, and patients after perianal abscess surgery were identified. 16S rRNA gene sequencing technology was used to detect the changes in the gut microbiota among 30 healthy individuals and 30 patients with perianal abscess before and after surgery. Venn diagrams and alpha diversity analyses indicated differences in the abundance and uniformity of gut microbiota between the healthy individuals and patients with perianal abscesses before and after surgery. Beta diversity analysis indicated that the grouping effects among the control, abscess, and surgery groups were good. The classification and compositional analysis showed significant differences in the gut microbiota between healthy individuals and patients with perianal abscesses before and after surgery. LEfSe analysis, random forest analysis, and ROC curve analysis showed that Klebsiella (AUC=0.7467) and Bilophila (AUC=0.72) could be potential biomarkers for the diagnosis of perianal abscess. The functional prediction results showed that the differential microbiota is significantly enriched in the pathways related to nutrition and drug metabolism. This study may have important implications for the clinical management and prognostic assessment of patients with perianal abscesses.

Nitrite-dependent anaerobic methane oxidation (n-damo) is a newly discovered biological process that couples anaerobic oxidation of methane (AOM) to nitrite reduction. In this study, three different inocula, methanogenic sludge, paddy soil, and freshwater sediment were used to enrich n-damo bacteria in three sequencing batch reactors (SBRs), and three n-damo enrichment cultures, C1, C2 and C3, were obtained, respectively. After 500 days of incubation, Methylomirabilis oxyfera-like bacteria and n-damo activities were observed in cultures C1, C2, and C3, and the specific activities were 0.8 ± 0.1, 1.4 ± 0.1, and 1.0 ± 0.1 μmol CH₄ h⁻¹ g⁻¹VSS, respectively. The copy numbers of 16S rRNA genes from cultures C1, C2, and C3 were 5.0 ± 0.4 × 10⁸, 6.1 ± 0.1 × 10⁹, and 1.0 ± 0.2 × 10⁹copies g⁻¹dry weight, respectively. The results indicated that paddy soil is an excellent inoculum for n-damo bacterial enrichment. This work expanded the alternative source of n-damo inoculum and benefited the further research of n-damo process.

Continuous chemical pollution is one of the most serious environmental problems in the Jiaojiang Estuary of the East Sea (China). This chemical pollution has significantly changed the estuarine environmental conditions and may have profoundly influenced the distribution of anammox bacterial communities in this estuary. Here, we investigated the influence of chemical pollution on the community composition, diversity and abundance of anammox bacteria in Jiaojiang estuarine sediments. Phylogenetic analysis of 16S rRNA genes showed that the majority of anammox bacterial sequences retrieved from the estuarine intertidal sediments were associated with Kuenenia. In contrast, different anammox communities composed of Brocadia, Kuenenia, Scalindua and Jettenia were found in the estuarine subtidal sediments. Redundancy analysis (RDA) indicated that the sediment nitrobenzene and organic content had significant impacts on the distribution of anammox communities in the intertidal sediments. Pearson correlation analysis showed that the diversity of anammox bacteria in the intertidal sediments was positively correlated with the organic content. In contrast, RDA results showed that the nitrobenzene content, NO(3)(-) concentration and salinity significantly influenced the distribution of anammox communities in the subtidal sediments. The diversity and relative abundance of anammox bacteria in the subtidal sediments were positively correlated with NO(3)(-) concentration.

Ammonia oxidation is performed by both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). To explore the effect of ammonia concentration on the population dynamic changes of ammonia-oxidizing microorganisms, we examined changes in the abundance and community composition of AOA and AOB in different layers. Most of the archaeal amoA sequences were Nitrosotalea-related and the proportion that Nitrosotalea cluster occupied decreased in the surface layer and increased in the deep layer during the cultivation process. Nitrosopumilus-related sequences were only detected in the deep layer in the first stage and disappeared later. Both phylogenetic and quantitative analysis showed that there were increased Nitrosomonas-related sequences appeared in the surface layer where the ammonia concentration was the highest. Both AOA and AOB OTU numbers in different layers decreased under selective pressure and then recovered. The potential nitrification rates were 25.06 µg · N · L(-1) · g(-1) dry soil · h(-1) in the mid layer which was higher than the other two layers. In general, obvious population dynamic changes were found for both AOA and AOB under the selective pressure of exogenous ammonia and the changes were different in three layers of the soil column.

Currently, little is understood about the role of different anaerobic oxidation of methane (AOM) pathways and their relative contributions in reducing CH4 emissions from rice fields. The potential rates of AOM caused by nitrate-, iron-, and sulfate-reduction, as well as the anaerobic methanotrophic (ANME-2d) archaeal absolute abundance and community composition were investigated across varying rice growth periods (tillering, jointing, flowering, and maturing) and soil layers (0–10, 10–20, 20–30, and 30–40 cm). The average potential rate of nitrate-AOM (2.73 nmol 13CO2 g-1 d-1) was significantly higher than those of iron- (1.15 nmol 13CO2 g-1 d-1) and sulfate-AOM (0.42 nmol 13CO2 g-1 d-1) across growth periods and soil layers. The AOM rates in surface soils (0–20 cm) and earlier periods (tillering and jointing) were significantly higher than those in deep soils (20–40 cm) and later periods (flowering and maturing), respectively. Differently, ANME-2d archaeal absolute abundance and community compositions were only significantly affected by soil layers, with the highest absolute abundance in the 10–20 cm layer. The organic carbon content and availability of electron acceptor were the primary factors governing the rates of different AOM pathways and community of ANME-2d archaea. Overall, this study provided the variation in AOM rates driven via multiple electron acceptors and ANME-2d archaeal community across rice growth periods and soil layers, and provided an important scientific basis for precise quantification of AOM as a potential CH4 sink in rice fields.

Candidatus Methylomirabilis-related bacteria conduct anaerobic oxidation of methane (AOM) coupling with NO 2 − reduction, and Candidatus Methanoperedens-related archaea perform AOM coupling with reduction of diverse electron acceptors, including NO 3 − , Fe (III), Mn (IV) and SO 4 2− . Application of nitrogen fertilization favors the growth of these methanotrophs in agricultural fields. Here, we explored the vertical variations in community structure and abundance of the two groups of methanotrophs in a nitrogen-rich vegetable field via using illumina MiSeq sequencing and quantitative PCR. The retrieved Methylomirabilis -related sequences had 91.12%-97.32% identity to the genomes of known Methylomirabilis species, and Methanoperedens -related sequences showed 85.49%-97.48% identity to the genomes of known Methanoperedens species which are capable of conducting AOM coupling with reduction of NO 3 − or Fe (III). The Methanoperedens -related archaeal diversity was significantly higher than Methylomirabilis- related bacteria, with totally 74 and 16 operational taxonomic units, respectively. In contrast, no significant difference in abundance between the bacteria (9.19 × 10 3 –3.83 × 10 5 copies g −1 dry soil) and the archaea (1.55 × 10 4 –3.24 × 10 5 copies g −1 dry soil) was observed. Furthermore, the abundance of both groups of methanotrophs exhibited a strong vertical variation, which peaked at 30–40 and 20–30 cm layers, respectively. Soil water content and pH were the key factors influencing Methylomirabilis -related bacterial diversity and abundance, respectively. For the Methanoperedens -related archaea, both soil pH and ammonium content contributed significantly to the changes of these archaeal diversity and abundance. Overall, we provide the first insights into the vertical distribution and regulation of Methylomirabilis -related bacteria and Methanoperedens -related archaea in vegetable soils. Key points • The archaeal diversity was significantly higher than bacterial. • There was no significant difference in the abundance between bacteria and archaea. • The abundance of bacteria and archaea peaked at 30–40 and 20–30 cm, respectively.

Nitrite-dependent anaerobic methane oxidation (N-DAMO), which couples anaerobic methane oxidation and nitrite reduction, is a recently discovered bioprocess coupling microbial nitrogen and carbon cycles. The discovery of this microbial process challenges the traditional knowledge of global methane sinks and nitrogen losses. In this study, the abundance and activity of N-DAMO bacteria were investigated and their contributions to methane sink and nitrogen loss were estimated in different seasons and different partitions of an intertidal zone of the East China Sea. The results showed that N-DAMO bacteria were extensively and continuously present in the intertidal zone, with the number of cells ranging from 5.5 × 10 4 to 2.8 × 10 5 copy g −1 soil and the potential activity ranging from 0.52 to 5.7 nmol CO 2  g −1 soil day −1 , contributing 5.0–36.6% of nitrite- and sulfate-dependent anaerobic methane oxidation in the intertidal zone. The N-DAMO activity and its contribution to the methane consumption were highest in the spring and in the low intertidal zone. These findings showed that the N-DAMO process is an important methane and nitrogen sink in the intertidal zone and varies with the seasons and the partitions of the intertidal zone.

The contribution of CH 4 emissions from paddy soils to greenhouse gas emissions is key in the evaluation of future climate change scenarios. Most studies in this field have investigated the effects of elevated CO 2 concentrations (e[CO 2 ]s) on CH 4 fluxes and methanogenic communities in paddy soils under constant CO 2 concentrations ([CO 2 ]s). However, atmospheric [CO 2 ] is gradually increasing and the relationship between future climate change and CH 4 emissions from paddy fields is poorly understood. This study explored the responses of CH 4 fluxes and methanogenic communities in paddy soils to different e[CO 2 ]s using open-top chambers. The rice biomass, CH 4 fluxes, methane production potential, and methanogenic characteristics were analyzed under CK (ambient [CO 2 ]), C 1 (e[CO 2 ] by 120 µmol mol –1 ), and C 2 (e[CO 2 ] by 200 µmol mol –1 ) treatments. The results indicated that the C 1 and C 2 treatments insignificantly increased the CH 4 flux in paddy fields. However, the C 1 treatment significantly increased the CH 4 flux/biomass at the elongation stage, while the C 2 treatment significantly increased the CH 4 flux/biomass at all of the growth stages. The C 1 and C 2 treatments had a positive effect on both methane production potential and methanogenic abundance at all of the growth stages, but this effect was not always significant. In addition, the C 1 and C 2 treatments significantly altered the methanogenic community structure at the elongation stage. Notably, there was a significant linear relationship between the CH 4 flux/biomass and [CO 2 ] at all of the growth stages; between the methane production potential and [CO 2 ] at the tillering, elongation, and milk-ripening stages; and between the mcrA g ene abundance and [CO 2 ] at the milk-ripening stage. A linear model based on rice biomass, methane production potential, and soil DOC concentration explained 72.7% of the variation in the CH 4 fluxes. Overall, the linear relationship between CH 4 fluxes and atmospheric [CO 2 ] levels was controlled by the rice biomass, soil carbon substrate, and methanogenic communities.