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The central carbon (C) metabolic network harvests energy to power the cell and feed biosynthesis for growth. In pure cultures, bacteria use some but not all of the network's major pathways, such as glycolysis and pentose phosphate and Entner-Doudoroff pathways. However, how these pathways are used in microorganisms in intact soil communities is unknown. Here, we analyzed the incorporation of 13 C from glucose isotopomers into phospholipid fatty acids. We showed that groups of Gram-positive and Gram-negative bacteria in an intact agricultural soil used different pathways to metabolize glucose. They also differed in C use efficiency (CUE), the efficiency with which a substrate is used for biosynthesis. Our results provide experimental evidence for diversity among microbes in the organization of their central carbon metabolic network and CUE under in situ conditions. These results have important implications for our understanding of how community composition affects soil C cycling and organic matter formation.

Agricultural and industrial activities have increased atmospheric nitrogen (N) deposition to ecosystems worldwide. N deposition can stimulate plant growth and soil carbon (C) input, enhancing soil C storage. Changes in microbial decomposition could also influence soil C storage, yet this influence has been difficult to discern, partly because of the variable effects of added N on the microbial enzymes involved. We show, using meta-analysis, that added N reduced the activity of lignin-modifying enzymes (LMEs), and that this N-induced enzyme suppression was associated with increases in soil C. In contrast, N-induced changes in cellulase activity were unrelated to changes in soil C. Moreover, the effects of added soil N on LME activity accounted for more of the variation in responses of soil C than a wide range of other environmental and experimental factors. Our results suggest that, through responses of a single enzyme system to added N, soil microorganisms drive long-term changes in soil C accumulation. Incorporating this microbial influence on ecosystem biogeochemistry into Earth system models could improve predictions of ecosystem C dynamics.

Carbon storage by ecosystems is valuable for climate protection. Biodiversity conservation may help increase carbon storage, but the value of this influence has been difficult to assess. We use plant, soil, and ecosystem carbon storage data from two grassland biodiversity experiments to show that greater species richness increases economic value: Increasing species richness from 1 to 10 had twice the economic value of increasing species richness from 1 to 2. The marginal value of each additional species declined as species accumulated, reflecting the nonlinear relationship between species richness and plant biomass production. Our demonstration of the economic value of biodiversity for enhancing carbon storage provides a foundation for assessing the value of biodiversity for decisions about land management. Combining carbon storage with other ecosystem services affected by biodiversity may well enhance the economic arguments for conservation even further.

Norby et al center their critique on the design of the data set and the response variable used. We address these criticisms and reinforce the conclusion that plants that associate with ectomycorrhizal fungi exhibit larger biomass and growth responses to elevated CO 2 compared with plants that associate with arbuscular mycorrhizae., (Copyright © 2017, American Association for the Advancement of Science.)

Plants buffer increasing atmospheric carbon dioxide (CO2) concentrations through enhanced growth, but the question whether nitrogen availability constrains the magnitude of this ecosystem service remains unresolved. Synthesizing experiments from around the world, we show that CO2 fertilization is best explained by a simple interaction between nitrogen availability and mycorrhizal association. Plant species that associate with ectomycorrhizal fungi show a strong biomass increase (30 ± 3%, P < 0.001) in response to elevated CO2 regardless of nitrogen availability, whereas low nitrogen availability limits CO2 fertilization (0 ± 5%, P = 0.946) in plants that associate with arbuscular mycorrhizal fungi. The incorporation of mycorrhizae in global carbon cycle models is feasible, and crucial if we are to accurately project ecosystem responses and feedbacks to climate change., (Copyright © 2016, American Association for the Advancement of Science.)

The human microbiome can play a key role in host susceptibility to pathogens, including in the nasal cavity, a site favored by Staphylococcus aureus. However, what determines our resident nasal microbiota-the host or the environment-and can interactions among nasal bacteria determine S. aureus colonization? Our study of 46 monozygotic and 43 dizygotic twin pairs revealed that nasal microbiota is an environmentally derived trait, but the host's sex and genetics significantly influence nasal bacterial density. Although specific taxa, including lactic acid bacteria, can determine S. aureus colonization, their negative interactions depend on thresholds of absolute abundance. These findings demonstrate that nasal microbiota is not fixed by host genetics and opens the possibility that nasal microbiota may be manipulated to prevent or eliminate S. aureus colonization.

Soils contain the largest pool of terrestrial organic carbon (C) and are a major source of atmospheric carbon dioxide (CO2). Thus, they may play a key role in modulating climate change. Rising atmospheric CO2 is expected to stimulate plant growth and soil C input but may also alter microbial decomposition. The combined effect of these responses on long-term C storage is unclear. Combining meta-analysis with data assimilation, we show that atmospheric CO2 enrichment stimulates both the input (+19.8%) and the turnover of C in soil (+16.5%). The increase in soil C turnover with rising CO2 leads to lower equilibrium soil C stocks than expected from the rise in soil C input alone, indicating that it is a general mechanism limiting C accumulation in soil.