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Abstract Aerobic methanotrophs are a specialized microbial group, catalyzing the oxidation of methane. Disturbance-induced loss of methanotroph diversity/abundance, thus results in the loss of this biological methane sink. Here, we synthesized and conceptualized the resilience of the methanotrophs to sporadic, recurring, and compounded disturbances in soils. The methanotrophs showed remarkable resilience to sporadic disturbances, recovering in activity and population size. However, activity was severely compromised when disturbance persisted or reoccurred at increasing frequency, and was significantly impaired following change in land use. Next, we consolidated the impact of agricultural practices after land conversion on the soil methane sink. The effects of key interventions (tillage, organic matter input, and cover cropping) where much knowledge has been gathered were considered. Pairwise comparisons of these interventions to nontreated agricultural soils indicate that the agriculture-induced impact on the methane sink depends on the cropping system, which can be associated to the physiology of the methanotrophs. The impact of agriculture is more evident in upland soils, where the methanotrophs play a more prominent role than the methanogens in modulating overall methane flux. Although resilient to sporadic disturbances, the methanotrophs are vulnerable to compounded disturbances induced by anthropogenic activities, significantly affecting the methane sink function. Synthesis and conceptualization of the response of aerobic methanotrophs to sporadic (one-off), recurring, and compounded disturbances, and their role as a methane sink in soils under agriculture management.

Abstract A viral shunt can occur when phages going through a lytic cycle, including lysogenic phages triggered by inducing agents (e.g. mitomycin C), results in host lysis and the release of cell constituents and virions. The impact of a viral shunt on the carbon, including methane cycle in soil systems is poorly understood. Here, we determined the effects of mitomycin C on the aerobic methanotrophs in a landfill cover soil. To an extent, our results support a mitomycin C-induced viral shunt, as indicated by the significantly higher viral-like particle (VLP) counts relative to bacteria, elevated nutrient concentrations (ammonium, succinate), and initially impaired microbial activities (methane uptake and microbial respiration) after mitomycin C addition. The trend in microbial activities at <2 days largely corresponded to the expression of the pmoA and 16S rRNA genes. Thereafter (>11 days), the active bacterial community composition significantly diverged in the mitomycin C-supplemented incubations, suggesting the differential impact of mitomycin C on the bacterial community. Collectively, we provide insight on the effects of mitomycin C, and potentially a viral shunt, on the bacteria in the soil environment. Mitomycin C can potentially induce a viral shunt, impacting soil microbial respiration and methane uptake, and modifies the active bacterial community composition, including the methanotrophs.

In the global effort to reduce anthropogenic methane emissions, millions of abandoned oil and gas wells are suspected to be prominent, although thus far often overlooked, methane sources. Recent studies have highlighted the hundreds of thousands of undocumented abandoned wells in North America as major methane sources, sometimes emitting up to several tons of methane per year. In Germany, approximately 25 000 abandoned wells have been described; these wells have been well documented, and the data are publicly available. Here, we present a methodological approach to assess emissions, particularly methane, from cut and buried abandoned wells, which are typical of wells in Germany. We sampled eight oil wells in a peat-rich environment, with four wells in a forest (referred to as Forest), three wells at an active peat extraction site (referred to as Peat), and one well in a meadow (referred to as Meadow). All three areas are underlain by peat. At each site, we sampled a 30 m x 30 m grid and a corresponding 20 m x 20 m reference grid. Three of the eight wells and reference sites exhibited net methane emissions. In each case, the reference sites emitted more methane than the respective well site, with the highest net emission (â¼ 110 nmol CH.sub.4 m.sup.-2 s.sup.-1) observed at one of these reference sites. All methane-emitting sites were located within the active peat extraction area. Detailed soil gas characterization revealed no methane-to-ethane or methane-to-propane ratios typical of reservoir gas; instead, it showed a typical biogenic composition and isotopic signature (mean [delta].sup.13 C-CH.sub.4 of -63 0/00). Thus, the escaping methane did not originate from the abandoned wells nor the associated oil reservoir. Furthermore, isotopic signatures of methane and carbon dioxide suggest that the methane from the peat extraction site was produced by acetoclastic methanogens, whereas the methane at the Meadow site was produced by hydrogenotrophic methanogens. However, our genetic analysis showed that both types of methanogens were present at both sites, suggesting that other factors control the dominant methane production pathway. Subsequent molecular biological studies confirmed that aerobic methanotrophic bacteria were also important and that their relative abundance was highest at the peat extraction site. Furthermore, the composition of the methanotrophic community varied between sites and depths. The aerobic methane oxidation rates were highest at the peat extraction site, potentially oxidizing a multiple of the emitted methane and, thus, likely providing an effective microbial methane filter.

Porcellio scaber (woodlice) are (sub-)surface-dwelling isopods, widely recognized as “soil bioengineers”, modifying the edaphic properties of their habitat, and affecting carbon and nitrogen mineralization that leads to greenhouse gas emissions. Yet, the impact of soil isopods on methane-cycling processes remains unknown. Using P. scaber as a model macroinvertebrate in a microcosm study, we determined how the isopod influences methane uptake and the associated interaction network in an agricultural soil. Stable isotope probing (SIP) with 13C-methane was combined to a co-occurrence network analysis to directly link activity to the methane-oxidizing community (bacteria and fungus) involved in the trophic interaction. Compared to microcosms without the isopod, P. scaber significantly induced methane uptake, associated to a more complex bacteria-bacteria and bacteria-fungi interaction, and modified the soil nutritional status. Interestingly, 13C was transferred via the methanotrophs into the fungi, concomitant to significantly higher fungal abundance in the P. scaber-impacted soil, indicating that the fungal community utilized methane-derived substrates in the food web along with bacteria. Taken together, results showed the relevance of P. scaber in modulating methanotrophic activity with implications for bacteria-fungus interaction.

The Munich ENU Mouse Mutagenesis Project within the German Human Genome Project is a phenotype-driven approach to produce, identify, and characterize new mouse mutants (Hrabe de Angelis and Balling 1998). The focus of the clinical-chemical screen is on laboratory diagnostic procedures (mainly bloodbased) suitable to detect hematological changes, defects of various organ systems, and changes in metabolic pathways and electrolyte homeostasis. The methods used are appropriate routine procedures, allowing the screening of large numbers of mice for a broad spectrum of clinical-chemical and hematological parameters. Since most inherited metabolic disorders in humans are known to lead directly or indirectly via altered organ function to changes in the parameters investigated (Fernandes et al. 1995; Saudubray and Charpentier 1995), this screen provides a comprehensive investigation of clinical phenotypes with known counterparts in humans.