The importance of environmental microbes for Drosophila melanogaster during seasonal macronutrient variability.

Experiments manipulating the nutritional environment and the associated microbiome of animals have demonstrated their importance for key fitness components. However, there is little information on how macronutrient composition and bacterial communities in natural food sources vary across seasons in nature and on how these factors affect the fitness components of insects. In this study, diet samples from an orchard compost heap, which is a natural habitat for many Drosophila species and other arthropods, were collected over 9 months covering all seasons in a temperate climate. We developed D. melanogaster on diet samples and investigated stress resistance and life-history traits as well as the microbial community of flies and compost. Nutrient and microbial community analysis of the diet samples showed marked differences in macronutrient composition and microbial community across seasons. However, except for the duration of development on these diet samples and Critical Thermal maximum, fly stress resistance and life-history traits were unaffected. The resulting differences in the fly microbial community were also more stable and less diverse than the microbial community of the diet samples. Our study suggests that when D. melanogaster are exposed to a vastly varying nutritional environment with a rich, diverse microbial community, the detrimental consequences of an unfavourable macronutrient composition are offset by the complex interactions between microbes and nutrients.

Is domestic agricultural production sufficient to meet national food nutrient needs in Brazil?

Reducing the impacts of agriculture on the environment is one of the greatest challenges of this century. In Brazil, it is often argued that more land use change is needed to achieve food security. However, analyses seeking to understand the dynamics between agricultural production for exports and food intended for the Brazilian population have not approached the question if national agriculture is sufficient to provide Brazilians with the necessary nutrients, according to nutritional recommendations. In this sense, we sought to combine supply and dietary requirements for food (calories and nutrients) to assess trends in nutrient production and how future population projections and possible changes in diets would affect land necessity for nutritional security. We use sub-national data on agricultural production, population, Food Balance Sheets from FAO, and a compilation of nutritional information on the Brazilian agricultural production. Our results show that, in the last three decades, Brazil produced enough food calories to feed on average 115% of its population. We found that the agricultural land in 2017, without any expansion, is sufficient to feed, at least, 105% of projected population in 2060, considering the same productivity and dietary patterns. In a vegan diet scenario, less than 10% of the land dedicated to agricultural production in the past 30 years would be required. Despite limitations on supplying certain micro-nutrients, a vegan diet would require even less land in the future. We conclude that Brazilian agriculture could deliver enough food to meet Brazilians' nutritional needs without further land expansion. Food production is compatible with environmental conservation in Brazil, especially if meat consumption is reduced.

Global associations between macronutrient supply and age-specific mortality.

Animal experiments have demonstrated that energy intake and the balance of macronutrients determine life span and patterns of age-specific mortality (ASM). Similar effects have also been detected in epidemiological studies in humans. Using global supply data and 1,879 life tables from 103 countries, we test for these effects at a macrolevel: between the nutrient supplies of nations and their patterns of ASM. We find that macronutrient supplies are strong predictors of ASM even after correction for time and economic factors. Globally, signatures of undernutrition are evident in the effects of low supply on life expectancy at birth and high mortality across ages, even as recently as 2016. However, in wealthy countries, the effects of overnutrition are prominent, where high supplies particularly from fats and carbohydrates are predicted to lead to high levels of mortality. Energy supplied at around 3,500 kcal/cap/d minimized mortality across ages. However, we show that the macronutrient composition of energy supply that minimizes mortality varies with age. In early life, 40 to 45% energy from each of fat and carbohydrate and 16% from protein minimizes mortality. In later life, replacing fat with carbohydrates to around 65% of total energy and reducing protein to 11% is associated with the lowest level of mortality. These results, particularly those regarding fats, accord both with experimental data from animals and within-country epidemiological studies on the association between macronutrient intake and risk of age-related chronic diseases.

Vectors with autonomy: what distinguishes animal-mediated nutrient transport from abiotic vectors?

Animal movements are important drivers of nutrient redistribution that can affect primary productivity and biodiversity across various spatial scales. Recent work indicates that incorporating these movements into ecosystem models can enhance our ability to predict the spatio-temporal distribution of nutrients. However, the role of animal behaviour in animal-mediated nutrient transport (i.e. active subsidies) remains under-explored. Here we review the current literature on active subsidies to show how the behaviour of active subsidy agents makes them both ecologically important and qualitatively distinct from abiotic processes (i.e. passive subsidies). We first propose that animal movement patterns can create similar ecological effects (i.e. press and pulse disturbances) in recipient ecosystems, which can be equal in magnitude to or greater than those of passive subsidies. We then highlight three key behavioural features distinguishing active subsidies. First, organisms can transport nutrients counter-directionally to abiotic forces and potential energy gradients (e.g. upstream). Second, unlike passive subsidies, organisms respond to the patterns of nutrients that they generate. Third, animal agents interact with each other. The latter two features can form positive- or negative-feedback loops, creating patterns in space or time that can reinforce nutrient hotspots in places of mass aggregations and/or create lasting impacts within ecosystems. Because human-driven changes can affect both the space-use of active subsidy species and their composition at both population (i.e. individual variation) and community levels (i.e. species interactions), predicting patterns in nutrient flows under future modified environmental conditions depends on understanding the behavioural mechanisms that underlie active subsidies and variation among agents' contributions. We conclude by advocating for the integration of animal behaviour, animal movement data, and individual variation into future conservation efforts in order to provide more accurate and realistic assessments of changing ecosystem function.

Consumption of Traditional and Indigenous Foods and Their Contribution to Nutrient Intake among Children and Women in Botswana.

In Botswana, traditional diets are gradually being replaced by westernized diets high in energy-dense and nutrient- poor, while micro nutrient deficiencies among the population remain. We determined the consumption of traditional and indigenous foods (TIF) and their contribution to nutrient intake among children and women in Botswana. TIF accounted for relatively high percentages of energy intake in children (41%) and women (36%) respectively. The mean intake of vitamin A in children and vitamin A and zinc in women was high from TIF compared to non-TIF. Research attention to determining the full potential of TIF in contributing to nutrition and health is warranted.

How leaking and overproducing resources affect the evolutionary robustness of cooperative cross-feeding.

Cooperative cross-feeding, a resource-exchange mutualism between microbes, is ubiquitous; however, models suggest it should be susceptible to cheating. Recent work suggested two novel mechanisms that could allow cross-feeders to exclude cheaters, even in the absence of tight coupling between cooperative organisms. The first is pattern formation, where cross-feeders form regular patterns so that their resources are separated and cheaters cannot obtain both. The second mechanism is neighbor uncertainty, where demographic stochasticity separates resources so cheaters cannot obtain both. Here we use a stochastic spatial model to test whether those mechanisms are evolutionarily stable, or whether they will collapse under gradual evolution towards reduced resource production. The answer depends on whether a microbe can make the resource for itself without sharing it. If it cannot (i.e. if producing more of a resource means sharing more of a resource), then both mechanisms continue to function. In this case, resource production directly benefits the individual, and cooperation is a byproduct. If microbes can make the resource without sharing it (i.e. if production is an altruistic trait), then neighbor uncertainty completely fails, and pattern formation is weakened. In this case, the costly trait has no direct benefit to the individual, and can only persist if cooperative organisms become associated with their partner. Thus, the novel mechanisms, which operate without tight associations, falter. These results have implications for synthetic ecology, as they suggest that how cross-feeding is engineered will impact its evolutionary stability.

Transient alleviation of tumor hypoxia during first days of antiangiogenic therapy as a result of therapy-induced alterations in nutrient supply and tumor metabolism - Analysis by mathematical modeling.

A number of experiments on mouse tumor models, as well as certain clinical data, have demonstrated, that antiangiogenic therapy can lead to transient improvement in tumor oxygenation, that allows to increase efficiency of following radiotherapy. In the majority of works, this phenomenon has been explained by enhanced tumor perfusion due to normalization of capillaries' structure, that results in elevated oxygen inflow in tumor. However, changes in tumor perfusion often haven't been directly measured in relevant works, moreover, antiangiogenic therapy has been proven to have ambiguous effect on tumor perfusion both in mouse tumor models and in clinics. Herein, we suggest that elevation of blood perfusion may be not the only reason for transient alleviation of tumor hypoxia, and that it may manifest itself even under unchanged tumor blood flow. We propose that it may be as well caused by the decrease in tumor oxygen consumption rate (OCR) due to the reduction of tumor proliferation level, caused by nutrient shortage in result of antiangiogenic treatment. We provide detailed explanation of this hypothesis and visualize it using a specially developed mathematical model, which takes into account basic features of tumor growth and antiangiogenic therapy. We investigate the influence of the model parameters on oxygen dynamics; demonstrate, that transient alleviation of tumor hypoxia occurs in a fairly wide range of physiologically justified values of parameters; and point out the major factors, that determine oxygen dynamics during antiangiogenic therapy.

How Temperature, Pond-Drying, and Nutrients Influence Parasite Infection and Pathology.

The rapid pace of environmental change is driving multi-faceted shifts in abiotic factors that influence parasite transmission. However, cumulative effects of these factors on wildlife diseases remain poorly understood. Here we used an information-theoretic approach to compare the relative influence of abiotic factors (temperature, diurnal temperature range, nutrients and pond-drying), on infection of snail and amphibian hosts by two trematode parasites (Ribeiroia ondatrae and Echinostoma spp.). A temperature shift from 20 to 25 °C was associated with an increase in infected snail prevalence of 10-20%, while overall snail densities declined by a factor of 6. Trematode infection abundance in frogs was best predicted by infected snail density, while Ribeiroia infection specifically also declined by half for each 10% reduction in pond perimeter, despite no effect of perimeter on the per snail release rate of cercariae. Both nutrient concentrations and Ribeiroia infection positively predicted amphibian deformities, potentially owing to reduced host tolerance or increased parasite virulence in more productive environments. For both parasites, temperature, pond-drying, and nutrients were influential at different points in the transmission cycle, highlighting the importance of detailed seasonal field studies that capture the importance of multiple drivers of infection dynamics and the mechanisms through which they operate.