Microbially enhanced methane uptake under warming enlarges ecosystem carbon sink in a Tibetan alpine grassland.

The alpine grasslands of the Tibetan Plateau store 23.2 Pg soil organic carbon, which becomes susceptible to microbial degradation with climate warming. However, accurate prediction of how the soil carbon stock changes under future climate warming is hampered by our limited understanding of belowground complex microbial communities. Here, we show that 4 years of warming strongly stimulated methane (CH4 ) uptake by 93.8% and aerobic respiration (CO2 ) by 11.3% in the soils of alpine grassland ecosystem. Due to no significant effects of warming on net ecosystem CO2 exchange (NEE), the warming-stimulated CH4 uptake enlarged the carbon sink capacity of whole ecosystem. Furthermore, precipitation alternation did not alter such warming effects, despite the significant effects of precipitation on NEE and soil CH4 fluxes were observed. Metagenomic sequencing revealed that warming led to significant shifts in the overall microbial community structure and the abundances of functional genes, which contrasted to no detectable changes after 2 years of warming. Carbohydrate utilization genes were significantly increased by warming, corresponding with significant increases in soil aerobic respiration. Increased methanotrophic genes and decreased methanogenic genes were observed under warming, which significantly (R2  = .59, p < .001) correlated with warming-enhanced CH4 uptakes. Furthermore, 212 metagenome-assembled genomes were recovered, including many populations involved in the degradation of various organic matter and a highly abundant methylotrophic population of the Methyloceanibacter genus. Collectively, our results provide compelling evidence that specific microbial functional traits for CH4 and CO2 cycling processes respond to climate warming with differential effects on soil greenhouse gas emissions. Alpine grasslands may play huge roles in mitigating climate warming through such microbially enhanced CH4 uptake.

Nitrogen addition and warming rapidly alter microbial community compositions in the mangrove sediment.

The mangrove ecosystem is an important CO2 sink with an extraordinarily high primary productivity. However, it is vulnerable to the impact of climate warming and eutrophication. While there has been extensive research on plant growth and greenhouse gas emission in mangrove ecosystems, microbial communities, the primary biogeochemical cycling drivers, are much less understood. Here, we examined whether short-term experimental treatments: (1) eutrophication with a supplement of 185 g N m-2·year-1 (N), (2) 3°C warming (W), and (3) the dual treatment of N and W (NW) were sufficient to alter microbial communities in the sediment. After 4 months of experiments, most environmental factors remained unchanged. However, N had significant, strong effects on bacterial, fungal, and functional community compositions, while the effects of W on microbial communities were weaker. N increased bacterial richness, phylogenetic diversity, and evenness, owing to stronger stochastic processes induced by eutrophication. There were no interactive effects of N and W on bacterial, fungal, and functional community compositions, suggesting that joint effects of N and W were additive. Concomitant with higher N2O efflux induced by N, the relative abundances of most bacterial nitrogen cycling genes were increased or remained changed by N. In contrast, N decreased or did not change those of most bacterial carbon degradation genes, while W increased or did not change the relative abundances of most of bacterial and fungal carbon degradation genes, implying higher carbon degradation potentials. As the most abundant inorganic nitrogenous species in mangrove sediment, ammonium was a key factor in shaping microbial functional communities. Collectively, our findings showed that microbial community compositions in the mangrove sediment were highly sensitive to short-term N and W treatments, giving rise to ecological consequences such as higher N2O efflux.

Microbial Functional Responses Explain Alpine Soil Carbon Fluxes under Future Climate Scenarios.

Soil microorganisms are sensitive to temperature in cold ecosystems, but it remains unclear how microbial responses are modulated by other important climate drivers, such as precipitation changes. Here, we examine the effects of six in situ warming and/or precipitation treatments in alpine grasslands on microbial communities, plants, and soil carbon fluxes. These treatments differentially affected soil carbon fluxes, gross primary production, and microbial communities. Variations of soil CO2 and CH4 fluxes across all sites significantly (r > 0.70, P < 0.050) correlated with relevant microbial functional abundances but not bacterial or fungal abundances. Given tight linkages between microbial functional traits and ecosystem functionality, we conclude that future soil carbon fluxes in alpine grasslands can be predicted by microbial carbon-degrading capacities.IMPORTANCE The warming pace in the Tibetan Plateau, which is predominantly occupied by grassland ecosystems, has been 0.2°C per decade in recent years, dwarfing the rate of global warming by a factor of 2. Many Earth system models project substantial carbon sequestration in Tibet, which has been observed. Here, we analyzed microbial communities under projected climate changes by 2100. As the soil "carbon pump," the growth and activity of microorganisms can largely influence soil carbon dynamics. However, microbial gene response to future climate scenarios is still obscure. We showed that the abundances of microbial functional genes, but not microbial taxonomy, were correlated with carbon fluxes and ecosystem multifunctionality. By identifying microbial traits linking to ecosystem functioning, our results can guide the assessment of future soil carbon fluxes in alpine grasslands, a critical step toward mitigating climate changes.

Environmental antibiotics drives the genetic functions of resistome dynamics.

The increasing prevalence of antibiotic-resistant microorganisms imposes a global threat to public health. The over reliant use of antibiotics in the food industry has contributed considerably to the dissemination of antibiotics into various environments, yet the mechanisms by which antibiotic dissemination influences the assembly of the microbial community continues to remain obscure. Here, we examine bacterial and fungal community assemblies in swine manure, compost, compost amended, and unamended agricultural soil in five suburban areas of Beijing, China. Total antibiotic concentration decreased by factors of 10-1000 from manure and compost to soils. The bacterial α-diversity was found to be low in manure and compost samples, while the fungal α-diversity was similar across all samples. We detected significantly (p < 0.05) higher relative abundances of well recognized pathogenic microbial taxa, virulence associated genes, and antibiotic resistance genes (ARGs) in manure and compost than those in agricultural soils, revealing the higher microbial capacity of pathogenicity, virulence and antibiotic resistance. Unexpectedly, the relative abundances of both bacterial and fungal taxa did not predict the antibiotic concentration. A possible explanation was that bacterial and fungal communities were mainly shaped by random assemblies. Rather, antibiotic concentration could be well predicted by relative abundances of antibiotic resistance, stress and virulence associated genes. Despite the weak interconnection between ARGs and the microbiome, we demonstrate that microbial genes should be the focal point in tracking the ecological effects of antibiotic dissemination by revealing microbial community patterns along the dissemination chain of antibiotics.

Variations of Soil Microbial Community Structures Beneath Broadleaved Forest Trees in Temperate and Subtropical Climate Zones.

Global warming has shifted climate zones poleward or upward. However, understanding the responses and mechanism of microbial community structure and functions relevant to natural climate zone succession is challenged by the high complexity of microbial communities. Here, we examined soil microbial community in three broadleaved forests located in the Wulu Mountain (WLM, temperate climate), Funiu Mountain (FNM, at the border of temperate and subtropical climate zones), or Shennongjia Mountain (SNJ, subtropical climate). Although plant species richness decreased with latitudes, the microbial taxonomic α-diversity increased with latitudes, concomitant with increases in soil total and available nitrogen and phosphorus contents. Phylogenetic NRI (Net Relatedness Index) values increased from -0.718 in temperate zone (WLM) to 1.042 in subtropical zone (SNJ), showing a shift from over dispersion to clustering likely caused by environmental filtering such as low pH and nutrients. Similarly, taxonomy-based association networks of subtropical forest samples were larger and tighter, suggesting clustering. In contrast, functional α-diversity was similar among three forests, but functional gene networks of the FNM forest significantly (P < 0.050) differed from the others. A significant correlation (R = 0.616, P < 0.001) between taxonomic and functional ß-diversity was observed only in the FNM forest, suggesting low functional redundancy at the border of climate zones. Using a strategy of space-for-time substitution, we predict that poleward climate range shift will lead to decreased microbial taxonomic α-diversities in broadleaved forest.

Macrophage migration inhibitory factor enhances lipopolysaccharide-induced fibroblast proliferation by inducing toll-like receptor 4.

BACKGROUND: Fibroblast proliferation is a common manifestation of chronic inflammatory diseases, including rheumatoid arthritis (RA), Crohn's disease and ulcerative colitis, etc. To alleviate patient suffering, the mechanism underlying fibroblast proliferation should be elucidated. METHODS: CCK-8 assay was used to assess the stimulatory effect of LPS and macrophage migration inhibitory factor (MIF) on fibroblast proliferation. Then, TLR4 expression on fibroblast cell membrane was carried out by confocal scanning microscopy. Finally, real-time fluorescent quantitative PCR and flow cytometry were applied to determine the expression of TLR4 after MIF challenge. RESULTS: LPS alone directly stimulated the fibroblast proliferation. In addition, MIF showed co-stimulatory effect on LPS-induced fibroblast proliferation. Interestingly, fibroblast overtly expressed TLR4 without stimulation. After MIF stimulation, real-time PCR showed TLR4 mRNA levels were increased by about 33% in the fibroblasts; in agreement, TLR4 expression on the fibroblast membrane was increased by about 20%, as shown by flow cytometry. CONCLUSIONS: These findings indicated MIF elevates TLR4 expression in fibroblast, enhancing LPS-induced cell proliferation.

Regulatory immune responses induced by IL-1 receptor antagonist in rheumatoid arthritis.

Anakinra, a human recombinant IL-1 receptor antagonist, is approved for the treatment of RA. In this study, 12 patients received the placebo plus MTX treatment, 38 patients received Anakinra combined with MTX treatment. Compared with the placebo plus MTX group, serum levels of IL-17, IFN-γ, IL-21 and IL-1ß significantly decreased, the percentages of Th17 cells and Th1 cells were lower and the percentage of Treg cells was higher after receiving Anakinra combined with MTX treatment. The observed regulatory immune responses collectively correlated with clinical improvement in treated patients. A substantial response, ACR 20 at 24 w were consistent with those at 12 w, 16 w and 20 w, and was accompanied by a marked improvement in RA related laboratory parameters. The study reveals that the combination of Anakinra and MTX is safe and well tolerated, which induces regulatory immune responses and significantly provides greater clinical benefit than the placebo plus MTX group.