Subsurface lithoautotrophic microbial ecosystems (SLiMEs) under oligotrophic conditions are typically supported by H 2 . Methanogens and sulfate reducers, and the respective energy processes, are thought to be the dominant players and have been the research foci. Recent investigations showed that, in some deep, fluid-filled fractures in the Witwatersrand Basin, South Africa, methanogens contribute <5% of the total DNA and appear to produce sufficient CH 4 to support the rest of the diverse community. This paradoxical situation reflects our lack of knowledge about the in situ metabolic diversity and the overall ecological trophic structure of SLiMEs. Here, we show the active metabolic processes and interactions in one of these communities by combining metatranscriptomic assemblies, metaproteomic and stable isotopic data, and thermodynamic modeling. Dominating the active community are four autotrophic β-proteobacterial genera that are capable of oxidizing sulfur by denitrification, a process that was previously unnoticed in the deep subsurface. They co-occur with sulfate reducers, anaerobic methane oxidizers, and methanogens, which each comprise <5% of the total community. Syntrophic interactions between these microbial groups remove thermodynamic bottlenecks and enable diverse metabolic reactions to occur under the oligotrophic conditions that dominate in the subsurface. The dominance of sulfur oxidizers is explained by the availability of electron donors and acceptors to these microorganisms and the ability of sulfur-oxidizing denitrifiers to gain energy through concomitant S and H 2 oxidation. We demonstrate that SLiMEs support taxonomically and metabolically diverse microorganisms, which, through developing syntrophic partnerships, overcome thermodynamic barriers imposed by the environmental conditions in the deep subsurface.active subsurface environment | metabolic interactions | sulfur-driven autotrophic denitrifiers | syntrophy | inverted biomass pyramid M icroorganisms living in deep-subsurface ecosystems acquire energy through chemosynthesis and carbon from organic or inorganic sources. Whereas heterotrophs use dissolved organic carbon (DOC) transported from the surface and/or produced in situ, detrital organic deposits buried along with the sediments, and hydrocarbons migrating into petroleum reservoirs, chemolithoautotrophs fix dissolved inorganic carbon (DIC). In oligotrophic systems, subsurface lithoautotrophic microbial ecosystems (SLiMEs) (1) that are fueled by H 2 support the occurrence of autotrophic methanogens, acetogens, and sulfate reducers (2-5). These environments can host highly diverse communities, consisting mostly of prokaryotes, but also multicellular microeukaryotes and viral particles (6-13). Due to the limitation of available nutrients and energy substrates in the oligotrophic subsurface, it is reasonable to hypothesize that subsurface inhabitants with diverse functional traits cooperate syntrophically to maximize energy yield SignificanceMicroorganisms are known to live in the deep ...

Abstract-Optimal scheduling of real-time tasks on multiprocessor systems is known to be computationally intractable for large task sets. Any practical scheduling algorithm for assigning realtime tasks to a multiprocessor system presents a trade-off between its computational complexity and its performance. In this study, new schedulability conditions are presented for homogeneous multiprocessor systems where individual processors execute the rate-monotonic scheduling algorithm. The conditions are used to develop new strategies for assigning real-time tasks to processors. The performance of the new strategies is shown to be significantly better than suggested by the existing literature. Under the realistic assumption that the load of each real-time task is small compared to the processing speed of each processor, it is shown that the processors can be almost fully utilized.

Atmospheric CH 4 is the greenhouse gas responsible for the second largest increase in direct radiative forcing since 1750 (https://www.esrl.noaa.gov/gmd/aggi/; Forster et al., 2007). Globally distributed long-term observations show that the atmospheric burden of CH 4 has been increasing since 2007 after a relatively stable period from 1999 to 2006 (Figure 1). Around the same time that the increase started, the ratio of stable carbon isotopes of CH 4 ( 13 C/ 12 C), denoted by δ 13 C-CH 4 , started to decrease after two centuries of increase (Ferretti et al., 2005;Michel et al., 2021) (Figure 1). Atmospheric CH 4 abundance and its associated δ 13 C-CH 4 result from the combined effect of emission and sink processes, including emissions from fossil sources, wetlands (WLs), rice, waste/landfills, ruminants, and biomass/biofuel burning (BB), and sinks from soil bacteria consumption, reactions with hydroxyl radicals (OH), chlorine radical (Cl), etc. (Saunois et al., 2020). Different CH 4 sources have distinct δ 13 C-CH 4 signatures over large spatial scales (Schwietzke et al., 2016) and different CH 4 sinks have different preference for oxidation of 12

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