Systematic comparison of unilamellar vesicles reveals that archaeal core lipid membranes are more permeable than bacterial membranes

This is the final version. Available on open access from the Public Library of Science via the DOI in this recordData Availability: All relevant data are within the paper's Supporting Information files. Numerical values for Fig 4 can be found at https://doi.org/10.6084/m9.figshare.22086647One of the deepest branches in the tree of life separates the Archaea from the Bacteria. These prokaryotic groups have distinct cellular systems including fundamentally different phospholipid membrane bilayers. This dichotomy has been termed the lipid divide and possibly bestows different biophysical and biochemical characteristics on each cell type. Classic experiments suggest that bacterial membranes (formed from lipids extracted from Escherichia coli, for example) show permeability to key metabolites comparable to archaeal membranes (formed from lipids extracted from Halobacterium salinarum), yet systematic analyses based on direct measurements of membrane permeability are absent. Here, we develop a new approach for assessing the membrane permeability of approximately 10 μm unilamellar vesicles, consisting of an aqueous medium enclosed by a single lipid bilayer. Comparing the permeability of 18 metabolites demonstrates that diether glycerol-1-phosphate lipids with methyl branches, often the most abundant membrane lipids of sampled archaea, are permeable to a wide range of compounds useful for core metabolic networks, including amino acids, sugars, and nucleobases. Permeability is significantly lower in diester glycerol-3-phosphate lipids without methyl branches, the common building block of bacterial membranes. To identify the membrane characteristics that determine permeability, we use this experimental platform to test a variety of lipid forms bearing a diversity of intermediate characteristics. We found that increased membrane permeability is dependent on both the methyl branches on the lipid tails and the ether bond between the tails and the head group, both of which are present on the archaeal phospholipids. These permeability differences must have had profound effects on the cell physiology and proteome evolution of early prokaryotic forms. To explore this further, we compare the abundance and distribution of transmembrane transporter-encoding protein families present on genomes sampled from across the prokaryotic tree of life. These data demonstrate that archaea tend to have a reduced repertoire of transporter gene families, consistent with increased membrane permeation. These results demonstrate that the lipid divide demarcates a clear difference in permeability function with implications for understanding some of the earliest transitions in cell origins and evolution.Gordon and Betty and Gordon Moore FoundationBiotechnology and Biological Sciences Research Council (BBSRC)European Union Horizon 2020Volkswagen FoundationMerton College, University of Oxford (NATI

Chemical and Metabolic Aspects of Antimetabolite Toxins Produced by Pseudomonas syringae Pathovars

Pseudomonas syringae is a phytopathogenic bacterium present in a wide variety of host plants where it causes diseases with economic impact. The symptoms produced by Pseudomonas syringae include chlorosis and necrosis of plant tissues, which are caused, in part, by antimetabolite toxins. This category of toxins, which includes tabtoxin, phaseolotoxin and mangotoxin, is produced by different pathovars of Pseudomonas syringae. These toxins are small peptidic molecules that target enzymes of amino acids’ biosynthetic pathways, inhibiting their activity and interfering in the general nitrogen metabolism. A general overview of the toxins’ chemistry, biosynthesis, activity, virulence and potential applications will be reviewed in this work

Producers Responding to Environmental Turbulence in the Greek Agricultural Supply Chain:Does Buyer Type Matter?

There are many changes in the EU Agricultural Supply Chain (ASC). These changes cause environmental turbulence for supply chain entities operating in this sector. In the Greek ASC, there is a significant decline in its performance in particular at producers’ level. Based on the Contingency Theory this paper aims to identify the relevant environmental turbulence factors in Greek ASC context from the producers’ perspective and ascertain their impact on producers based on their choice of buyer type i.e. collaboration type. Twenty in-depth semi-structured interviews were conducted with Greek ASC producers. Thematic analysis was used to analyse the interviews. The findings suggest the existence of six major environmental turbulence factors at producers’ level which are: regulatory, market, competitive, weather, economic and political turbulence factors. Producers selling their products to cooperatives were found to be significantly impacted by the different environmental turbulence factors. Future research directions as well as managerial and policy implications are identified

Doubly Uniparental Inheritance of Mitochondria As a Model System for Studying Germ Line Formation

BACKGROUND: Doubly Uniparental Inheritance (DUI) of mitochondria occurs when both mothers and fathers are capable of transmitting mitochondria to their offspring, in contrast to the typical Strictly Maternal Inheritance (SMI). DUI was found in some bivalve molluscs, in which two mitochondrial genomes are inherited, one through eggs, the other through sperm. During male embryo development, spermatozoon mitochondria aggregate in proximity of the first cleavage furrow and end up in the primordial germ cells, while they are dispersed in female embryos. METHODOLOGY/PRINCIPAL FINDINGS: We used MitoTracker, microtubule staining and transmission electron microscopy to examine the mechanisms of this unusual distribution of sperm mitochondria in the DUI species Ruditapes philippinarum. Our results suggest that in male embryos the midbody deriving from the mitotic spindle of the first division concurs in positioning the aggregate of sperm mitochondria. Furthermore, an immunocytochemical analysis showed that the germ line determinant Vasa segregates close to the first cleavage furrow. CONCLUSIONS/SIGNIFICANCE: In DUI male embryos, spermatozoon mitochondria aggregate in a stable area on the animal-vegetal axis: in organisms with spiral segmentation this zone is not involved in cleavage, so the aggregation is maintained. Moreover, sperm mitochondria reach the same embryonic area in which also germ plasm is transferred. In 2-blastomere embryos, the segregation of sperm mitochondria in the same region with Vasa suggests their contribution in male germ line formation. In DUI male embryos, M-type mitochondria must be recognized by egg factors to be actively transferred in the germ line, where they become dominant replacing the Balbiani body mitochondria. The typical features of germ line assembly point to a common biological mechanism shared by DUI and SMI organisms. Although the molecular dynamics of the segregation of sperm mitochondria in DUI species are unknown, they could be a variation of the mechanism regulating the mitochondrial bottleneck in all metazoans

The BRIDGE HadCM3 family of climate models: HadCM3@Bristol v1.0

Understanding natural and anthropogenic climate change processes involves using computational models that represent the main components of the Earth system: the atmosphere, ocean, sea ice, and land surface. These models have become increasingly computationally expensive as resolution is increased and more complex process representations are included. However, to gain robust insight into how climate may respond to a given forcing, and to meaningfully quantify the associated uncertainty, it is often required to use either or both ensemble approaches and very long integrations. For this reason, more computationally efficient models can be very valuable tools. Here we provide a comprehensive overview of the suite of climate models based around the HadCM3 coupled general circulation model. This model was developed at the UK Met Office and has been heavily used during the last 15 years for a range of future (and past) climate change studies, but has now been largely superseded for many scientific studies by more recently developed models. However, it continues to be extensively used by various institutions, including the BRIDGE (Bristol Research Initiative for the Dynamic Global Environment) research group at the University of Bristol, who have made modest adaptations to the base HadCM3 model over time. These adaptations mean that the original documentation is not entirely representative, and several other relatively undocumented configurations are in use. We therefore describe the key features of a number of configurations of the HadCM3 climate model family, which together make up HadCM3@Bristol version 1.0. In order to differentiate variants that have undergone development at BRIDGE, we have introduced the letter B into the model nomenclature. We include descriptions of the atmosphere- only model (HadAM3B), the coupled model with a low-resolution ocean (HadCM3BL), the high-resolution atmosphere- only model (HadAM3BH), and the regional model (HadRM3B). These also include three versions of the land surface scheme. By comparing with observational datasets, we show that these models produce a good representation of many aspects of the climate system, including the land and sea surface temperatures, precipitation, ocean circulation, and vegetation. This evaluation, combined with the relatively fast computational speed (up to 1000 times faster than some CMIP6 models), motivates continued development and scientific use of the HadCM3B family of coupled climate models, predominantly for quantifying uncertainty and for long multi-millennial-scale simulations

Les lomasomes du

Les hyphes du Sporotrichum schenckii ont été étudiées en coupes ultrafines, au microscope électronique. Les articles contiennent des lomasomes typiques. A partir de ces observations faites sur l’ultrastructure, l’évolution et les fonctions de ces organites sont envisagées

Existence de structures myéliniques chez les champignons

Les auteurs ont mis en évidence, grâce au microscope électronique, des corps multilamellaires chez Sporotrichum schenckii (Hetkoen et Perkins, 1900), après une double fixation à la glutaraldéhyde et au tétroxyde d’osmium. Ces organites sont observés dans la portion distale des hyphes jeunes. Leur taille varie de 120 à 1.400 millimicrons. Leur structure est très polymorphe. Ils sont constitués d’un nombre varié de lamelles sombres, séparées par des espaces clairs. On trouve les corps myéliniques en plein hyaloplasme, à l’intérieur des vacuoles ou attenant à elles, à l’intérieur des mitochondries, au contact du noyau. Les structures multilamellaires semblent dériver de feuillets empilés du réticulum endoplasmique, perdant peu à peu leurs ribosomes. Leur présence dans les cellules jeunes pourrait témoigner d’un mode d’utilisation de matériaux lipidiques trop abondamment synthétisés