Dual function of OmpM as outer membrane tether and nutrient uptake channel in diderm Firmicutes.

The outer membrane (OM) in diderm, or Gram-negative, bacteria must be tethered to peptidoglycan for mechanical stability and to maintain cell morphology. Most diderm phyla from the Terrabacteria group have recently been shown to lack well-characterised OM attachment systems, but instead have OmpM, which could represent an ancestral tethering system in bacteria. Here, we have determined the structure of the most abundant OmpM protein from Veillonella parvula (diderm Firmicutes) by single particle cryogenic electron microscopy.

Total synthesis and mechanism of action of the antibiotic armeniaspirol A.

Emerging antimicrobial resistance urges the discovery of antibiotics with unexplored, resistance-breaking mechanisms. Armeniaspirols represent a novel class of antibiotics with a unique spiro[4.4]non-8-ene scaffold and potent activities against Gram-positive pathogens.

Acquisition of ionic copper by the bacterial outer membrane protein OprC through a novel binding site.

Copper, while toxic in excess, is an essential micronutrient in all kingdoms of life due to its essential role in the structure and function of many proteins. Proteins mediating ionic copper import have been characterised in detail for eukaryotes, but much less so for prokaryotes. In particular, it is still unclear whether and how gram-negative bacteria acquire ionic copper.

The 2018 correlative microscopy techniques roadmap.

Developments in microscopy have been instrumental to progress in the life sciences, and many new techniques have been introduced and led to new discoveries throughout the last century. A wide and diverse range of methodologies is now available, including electron microscopy, atomic force microscopy, magnetic resonance imaging, small-angle x-ray scattering and multiple super-resolution fluorescence techniques, and each of these methods provides valuable read-outs to meet the demands set by the samples under study. Yet, the investigation of cell development requires a multi-parametric approach to address both the structure and spatio-temporal organization of organelles, and also the transduction of chemical signals and forces involved in cell-cell interactions.

Small-Molecule Permeation across Membrane Channels: Chemical Modification to Quantify Transport across OmpF.

Biological channels facilitate the exchange of molecules across membranes, but general tools to quantify transport are missing. Electrophysiology is the method of choice to study the functional properties of channels. However, analyzing the current fluctuation of channels typically does not identify successful transport, that is, distinguishing translocation from binding.

Mechanistic aspects of maltotriose-conjugate translocation to the Gram-negative bacteria cytoplasm.

Small molecule accumulation in Gram-negative bacteria is a key challenge to discover novel antibiotics, because of their two membranes and efflux pumps expelling toxic molecules. An approach to overcome this challenge is to hijack uptake pathways so that bacterial transporters shuttle the antibiotic to the cytoplasm. Here, we have characterized maltodextrin-fluorophore conjugates that can pass through both the outer and inner membranes mediated by components of the maltose regulon.

A Multidisciplinary Approach toward Identification of Antibiotic Scaffolds for Acinetobacter baumannii.

Research efforts to discover potential new antibiotics for Gram-negative bacteria suffer from high attrition rates due to the synergistic action of efflux systems and the limited permeability of the outer membrane (OM). One strategy to overcome the OM permeability barrier is to identify small molecules that are natural substrates for abundant OM channels and use such compounds as scaffolds for the design of efficiently permeating antibacterials. Here we present a multidisciplinary approach to identify such potential small-molecule scaffolds.

Unusual Constriction Zones in the Major Porins OmpU and OmpT from Vibrio cholerae.

The outer membranes (OM) of many Gram-negative bacteria contain general porins, which form nonspecific, large-diameter channels for the diffusional uptake of small molecules required for cell growth and function. While the porins of Enterobacteriaceae (e.g.

Understanding Carbapenem Translocation through OccD3 (OpdP) of Pseudomonas aeruginosa.

Pseudomonas aeruginosa utilizes a plethora of substrate specific channels for the uptake of small nutrients. OccD3 (OpdP or PA4501) is an OprD-like arginine uptake channel of P. aeruginosa whose role has been implicated in carbapenem uptake.

Structural basis for nutrient acquisition by dominant members of the human gut microbiota.

The human large intestine is populated by a high density of microorganisms, collectively termed the colonic microbiota, which has an important role in human health and nutrition. The survival of microbiota members from the dominant Gram-negative phylum Bacteroidetes depends on their ability to degrade dietary glycans that cannot be metabolized by the host. The genes encoding proteins involved in the degradation of specific glycans are organized into co-regulated polysaccharide utilization loci, with the archetypal locus sus (for starch utilisation system) encoding seven proteins, SusA-SusG.

Large-Conductance Transmembrane Porin Made from DNA Origami.

DNA nanotechnology allows for the creation of three-dimensional structures at nanometer scale. Here, we use DNA to build the largest synthetic pore in a lipid membrane to date, approaching the dimensions of the nuclear pore complex and increasing the pore-area and the conductance 10-fold compared to previous man-made channels. In our design, 19 cholesterol tags anchor a megadalton funnel-shaped DNA origami porin in a lipid bilayer membrane.

Ion Channels Made from a Single Membrane-Spanning DNA Duplex.

Because of their hollow interior, transmembrane channels are capable of opening up pathways for ions across lipid membranes of living cells. Here, we demonstrate ion conduction induced by a single DNA duplex that lacks a hollow central channel. Decorated with six porpyrin-tags, our duplex is designed to span lipid membranes.

Role of Electroosmosis in the Permeation of Neutral Molecules: CymA and Cyclodextrin as an Example.

To quantify the flow of small uncharged molecules into and across nanopores, one often uses ion currents. The respective ion-current fluctuations caused by the presence of the analyte make it possible to draw some conclusions about the direction and magnitude of the analyte flow. However, often this flow appears to be asymmetric with respect to the applied voltage.

Structural Insights into Outer Membrane Permeability of Acinetobacter baumannii.

Bacterial resistance against antibiotics is an increasing global health problem. In Gram-negative bacteria the low permeability of the outer membrane (OM) is a major factor contributing to resistance, making it important to understand channel-mediated small-molecule passage of the OM. Acinetobacter baumannii has five Occ (OM carboxylate channel) proteins, which collectively are of major importance for the entry of small molecules.

Crystal structure of a COG4313 outer membrane channel.

COG4313 proteins form a large and widespread family of outer membrane channels and have been implicated in the uptake of a variety of hydrophobic molecules. Structure-function studies of this protein family have so far been hampered by a lack of structural information. Here we present the X-ray crystal structure of Pput2725 from the biodegrader Pseudomonas putida F1, a COG4313 channel of unknown function, using data to 2.