Genome-driven evolutionary game theory helps understand the rise of metabolic interdependencies in microbial communities

Metabolite exchanges in microbial communities give rise to ecological interactions that govern ecosystem diversity and stability. It is unclear, however, how the rise of these interactions varies across metabolites and organisms. Here we address this question by integrating genome-scale models of metabolism with evolutionary game theory. Specifically, we use microbial fitness values estimated by metabolic models to infer evolutionarily stable interactions in multi-species microbial “games”. We first validate our approach using a well-characterized yeast cheater-cooperator system. We next perform over 80,000 in silico experiments to infer how metabolic interdependencies mediated by amino acid leakage in Escherichia coli vary across 189 amino acid pairs. While most pairs display shared patterns of inter-species interactions, multiple deviations are caused by pleiotropy and epistasis in metabolism. Furthermore, simulated invasion experiments reveal possible paths to obligate cross-feeding. Our study provides genomically driven insight into the rise of ecological interactions, with implications for microbiome research and synthetic ecology.We gratefully acknowledge funding from the Defense Advanced Research Projects Agency (Purchase Request No. HR0011515303, Contract No. HR0011-15-C-0091), the U.S. Department of Energy (Grants DE-SC0004962 and DE-SC0012627), the NIH (Grants 5R01DE024468 and R01GM121950), the national Science Foundation (Grants 1457695 and NSFOCE-BSF 1635070), MURI Grant W911NF-12-1-0390, the Human Frontiers Science Program (grant RGP0020/2016), and the Boston University Interdisciplinary Biomedical Research Office ARC grant on Systems Biology Approaches to Microbiome Research. We also thank Dr Kirill Korolev and members of the Segre Lab for their invaluable feedback on this work. (HR0011515303 - Defense Advanced Research Projects Agency; HR0011-15-C-0091 - Defense Advanced Research Projects Agency; DE-SC0004962 - U.S. Department of Energy; DE-SC0012627 - U.S. Department of Energy; 5R01DE024468 - NIH; R01GM121950 - NIH; 1457695 - national Science Foundation; NSFOCE-BSF 1635070 - national Science Foundation; W911NF-12-1-0390 - MURI; RGP0020/2016 - Human Frontiers Science Program; Boston University Interdisciplinary Biomedical Research Office ARC)Published versio

Do overlapping property rights reduce agricultural investment ? evidence from Uganda

The need for land-related investment to ensure sustainable land management and increase productivity of land use is widely recognized. However, there is little rigorous evidence on the effects of property rights for increasing agricultural productivity and contributing toward poverty reduction in Africa. Whether and by how much overlapping property rights reduce investment incentives, and the scope for policies to counter such disincentives, are thus important policy issues. Using information on parcels under ownership and usufruct by the same household from a nationally representative survey in Uganda, the authors find significant disincentives associated with overlapping property rights on short and long-term investments. The paper combines this result with information on crop productivity to obtain a rough estimate of the magnitudes involved. The authors make suggestions on ways to eliminate such inefficiencies.Wetlands,Labor Policies,Common Property Resource Development,,Municipal Housing and Land

Environmental and Gender Impacts of Land Tenure Regularization in Africa

Although recent developments greatly increased interest in African land tenure, few models to address these issues at the required scale have been identified or evaluated. Rwanda.s nation-wide land tenure regularization programme is of great interest. A discontinuity design with spatial fixed effects that is used to evaluate the pilot for this programme points to three main effects; namely, (i) improved land access for legally married women and better recordation of inheritance rights; (ii) significant and large investment impacts that are particularly pronounced for women; and (iii) a reduction in land market activity rather than distress sales. Implications for programme design and policy are discussed.gender, agricultural investment, land administration, Rwanda

Topological Superconductivity and Majorana Fermions in RKKY Systems

We consider quasi one-dimensional RKKY systems in proximity to an s-wave superconductor. We show that a $2k_F$-peak in the spin susceptibility of the superconductor in the one-dimensional limit supports helical order of localized magnetic moments via RKKY interaction, where $k_F$ is the Fermi wavevector. The magnetic helix is equivalent to a uniform magnetic field and very strong spin-orbit interaction (SOI) with an effective SOI length $1/2k_F$. We find the conditions to establish such a magnetic state in atomic chains and semiconducting nanowires with magnetic atoms or nuclear spins. Generically, these systems are in a topological phase with Majorana fermions. The inherent self-tuning of the helix to $2k_F$ eliminates the need to tune the chemical potential

Calidad de Vida: An Exploratory Investigation of Latino Breast Cancer Survivors and Intimate Partners

Advances in addressing psychosocial issues related to cancer treatment and prevention are not reaching all survivors equally. Latina breast cancer survivors and intimate partners are underrepresented in psychosocial interventions, and there is a scarcity of research on the influence of cancer on Latino couples’ quality of life. The purpose of this manuscript is to present findings from a trans-linguistic, dyadic qualitative research study aimed at exploring the influence of cancer on quality of life for Latina breast cancer survivors and their intimate partners. Results highlight several areas that are helpful and hindering to supporting survivorship

Productivity effects of land rental markets in Ethiopia : Evidence from a matched tenant-landlord sample

As countries increasingly strive to transform their economies from agriculture-based into a diversified one, land rental will become of greater importance. It will thus be critical to complement research on the efficiency of specific land rental arrangements -- such as sharecropping -- with an inquiry into the broader productivity impacts of the land rental market. Plot-level data for a matched landlord-tenant sample in an environment where sharecropping dominates allows this paper to explore both issues. The authors find that pure output sharing leads to significantly lower levels of efficiency that can be attenuated by monitoring while the inefficiency disappears if inputs are shared as well. Rentals transfer land to more productive producers but realization of this productivity advantage is prevented by the inefficiency of contractual arrangements, suggesting changes that would prompt adoption of different contractual arrangements could have significant benefits.Labor Policies,Municipal Housing and Land,Economic Theory&Research,Land and Real Estate Development,Real Estate Development