Evolutionary transitions in bacterial symbiosis.

Diverse bacterial lineages form beneficial infections with eukaryotic hosts. The origins, evolution, and breakdown of these mutualisms represent important evolutionary transitions. To examine these key events, we synthesize data from diverse interactions between bacteria and eukaryote hosts.

Amphipols from A to Z.

Amphipols (APols) are short amphipathic polymers that can substitute for detergents to keep integral membrane proteins (MPs) water soluble. In this review, we discuss their structure and solution behavior; the way they associate with MPs; and the structure, dynamics, and solution properties of the resulting complexes. All MPs tested to date form water-soluble complexes with APols, and their biochemical stability is in general greatly improved compared with MPs in detergent solutions.

Determination of electron density profiles and area from simulations of undulating membranes.

The traditional method for extracting electron density and other transmembrane profiles from molecular dynamics simulations of lipid bilayers fails for large bilayer systems, because it assumes a flat reference surface that does not take into account long wavelength undulations. We have developed what we believe to be a novel set of methods to characterize these undulations and extract the underlying profiles in the large systems. Our approach first obtains an undulation reference surface for each frame in the simulation and subsequently isolates the long-wavelength undulations by filtering out the intrinsic short wavelength modes.

Interpretation of fluctuation spectra in lipid bilayer simulations.

Atomic resolution and coarse-grained simulations of dimyristoylphosphatidylcholine lipid bilayers were analyzed for fluctuations perpendicular to the bilayer using a completely Fourier-based method. We find that the fluctuation spectrum of motions perpendicular to the bilayer can be decomposed into just two parts: 1), a pure undulation spectrum proportional to q(-4) that dominates in the small-q regime; and 2), a molecular density structure factor contribution that dominates in the large-q regime. There is no need for a term proportional to q(-2) that has been postulated for protrusion fluctuations and that appeared to have been necessary to fit the spectrum for intermediate q.

Interleaflet interaction and asymmetry in phase separated lipid bilayers: molecular dynamics simulations.

In order to investigate experimentally inaccessible, molecular-level detail regarding interleaflet interaction in membranes, we have run an extensive series of coarse-grained molecular dynamics simulations of phase separated lipid bilayers. The simulations are motivated by differences in lipid and cholesterol composition in the inner and outer leaflets of biological membranes. Over the past several years, this phenomenon has inspired a series of experiments in model membrane systems which have explored the effects of lipid compositional asymmetry in the two leaflets.

Inclusive fitness theory and eusociality.

Arising from M. A. Nowak, C.

New paradigms for the evolution of beneficial infections.

A longstanding paradigm predicts that microbial parasites and mutualists exhibit disparate evolutionary patterns. Parasites are predicted to promote arms races with hosts, rapid evolution and sexual recombination. By contrast, mutualists have been linked with beneficial coadaptation, evolutionary stasis and asexuality.

Climate for evidence-informed health systems: A print media analysis in 44 low- and middle-income countries that host knowledge-translation platforms.

Background: We conducted a print media analysis in 44 countries in Africa, the Americas, Asia, and the Eastern Mediterranean in order to understand one dimension of the climate for evidence-informed health systems and to provide a baseline for an evaluation of knowledge-translation platforms. Our focus was whether and how policymakers, stakeholders, and researchers talk in the media about three topics: policy priorities in the health sector, health research evidence, and policy dialogues regarding health issues.

Methods: We developed a search strategy consisting of three progressively more delimited phases.

Expansion of cancer care and control in countries of low and middle income: a call to action.

Substantial inequalities exist in cancer survival rates across countries. In addition to prevention of new cancers by reduction of risk factors, strategies are needed to close the gap between developed and developing countries in cancer survival and the effects of the disease on human suffering. We challenge the public health community's assumption that cancers will remain untreated in poor countries, and note the analogy to similarly unfounded arguments from more than a decade ago against provision of HIV treatment.

Monitoring the world's agriculture.

To feed the world without further damaging the planet, Jeffrey Sachs and 24 foodsystem experts call for a global data collection and dissemination network to track the myriad impacts of different farming practices.

Host control over infection and proliferation of a cheater symbiont.

Host control mechanisms are thought to be critical for selecting against cheater mutants in symbiont populations. Here, we provide the first experimental test of a legume host's ability to constrain the infection and proliferation of a native-occurring rhizobial cheater. Lotus strigosus hosts were experimentally inoculated with pairs of Bradyrhizobium strains that naturally vary in symbiotic benefit, including a cheater strain that proliferates in the roots of singly infected hosts, yet provides zero growth benefits.

Origins of cheating and loss of symbiosis in wild Bradyrhizobium.

Rhizobial bacteria nodulate legume roots and fix nitrogen in exchange for photosynthates. These symbionts are infectiously acquired from the environment and in such cases selection models predict evolutionary spread of uncooperative mutants. Uncooperative rhizobia - including nonfixing and non-nodulating strains - appear common in agriculture, yet their population biology and origins remain unknown in natural soils.