Bioenergetic mapping of 'healthy microbiomes' via compound processing potential imprinted in gut and soil metagenomes.

Despite mounting evidence of their importance in human health and ecosystem functioning, the definition and measurement of 'healthy microbiomes' remain unclear. More advanced knowledge exists on health associations for compounds used or produced by microbes. Environmental microbiome exposures (especially via soils) also help shape, and may supplement, the functional capacity of human microbiomes. Given the synchronous interaction between microbes, their feedstocks, and micro-environments, with functional genes facilitating chemical transformations, our objective was to examine microbiomes in terms of their capacity to process compounds relevant to human health. Here we integrate functional genomics and biochemistry frameworks to derive new quantitative measures of in silico potential for human gut and environmental soil metagenomes to process a panel of major compound classes (e.g., lipids, carbohydrates) and selected biomolecules (e.g., vitamins, short-chain fatty acids) linked to human health. Metagenome functional potential profile data were translated into a universal compound mapping 'landscape' based on bioenergetic van Krevelen mapping of function-level meta-compounds and corresponding functional relative abundances, reflecting imprinted genetic capacity of microbiomes to metabolize an array of different compounds. We show that measures of 'compound processing potential' associated with human health and disease (examining atherosclerotic cardiovascular disease, colorectal cancer, type 2 diabetes and anxious-depressive behavior case studies), and displayed seemingly predictable shifts along gradients of ecological disturbance in plant-soil ecosystems (three case studies). Ecosystem quality explained 60-92 % of variation in soil metagenome compound processing potential measures in a post-mining restoration case study dataset. With growing knowledge of the varying proficiency of environmental microbiota to process human health associated compounds, we might design environmental interventions or nature prescriptions to modulate our exposures, thereby advancing microbiota-oriented approaches to human health. Compound processing potential offers a simplified, integrative approach for applying metagenomics in ongoing efforts to understand and quantify the role of microbiota in environmental- and human-health.

Chronic dryness and wetness and especially pulsed drought threaten a generalist arthropod herbivore.

Under climate change, both wetter and drier conditions, as well as an increase in extreme events like floods or droughts are projected for many areas. So far, studies only investigate the impact of drier or wetter conditions at a single stress severity level but do not consider how different intensities and types of changes affect insect herbivores feeding on stressed plants. Further, how effects of acute stress pulses differ from milder, chronic soil moisture stress is unclear. We investigated how changing soil moisture conditions affect a generalist insect herbivore feeding on grassland plants. We transplanted multi-species sections of grassland into pots and subjected them to different intensities and durations of flooding and drying stress. We compared effects of short, extreme drought and flooding pulses against the effects of milder, but chronic stress. Constantly drier conditions decreased plant and herbivore performance at all levels of stress severity. Severe permanent wetness did not affect plant growth, but decreased pupal weight (- 23%) and survival of larvae (- 34%). Extreme pulsed drought exacerbated negative effects of chronic drying, as most larvae died before they could benefit from rewetting plants after the drought (94% mortality). Pulsed flooding did not affect plants or larval development more than chronic severe wetness. Our findings imply that plant stress negatively affects generalist chewing herbivores, even with mixed diets. Both drier and severely wet, but not mildly wetter conditions, will reduce survival of some species. Especially, extreme droughts appear to have strong negative effects on generalist grassland herbivores.