Biofouling resistant materials based on micro‐structured surfaces with liquid‐repellent properties

Adhesion of contaminants on various polymer-based devices during fluid-substrate interactions is a common problem that can cause biofouling andcorrosion. In this study, hierarchical structures with submicron features onpolypropylene (PP), high-density polyethylene (HDPE), and polycarbonate (PC)are fabricated by femtosecond laser ablation. The effect of the hierarchicalstructures on surface wettability, droplet impact, and bacterial attachment hasbeen examined. Our results demonstrate that the structured polymeric sub-strates facilitate large contact angles and minimal interfacial adhesion, allowingdroplets to roll off at a low angle of inclination below 5◦. Further, rendering thehierarchicalstructureswithalow-surface-energycoatingcanenablethesurfacesto exhibit superamphiphobic properties. The low interfacial adhesion properties,as accounted by the large contact angles and small contact angle hysteresis, ofsuch surfaces prevent bacterial attachment and biofilm formation. The findingsprovide a design principle for creating affordable biofouling resistant surfaceswith a submicron topography hat can be used for engineering and biomedical devices

Membrane staining and phospholipid tracking in Pseudomonas aeruginosa PAO1 using the phosphatidylcholine mimic propargyl-choline

The use of membrane-specific dyes for in vivo fluorescent microscopy is commonplace. However, most of these reagents are non-specific and cannot track specific lipid species movement, instead often acting as non-covalent lipid associated probes or requiring uptake of whole lipids and acyl tails into the membrane. This issue has been solved in eukaryotic cell biology by use of click-chemistry liable phospholipid headgroup pulse-labels. Here we describe a method for in vivo phospholipid labelling by fluorescent imaging in Pseudomonas aeruginosa using a phosphatidylcholine (PC) mimic, “propargyl-choline”(PCho). This click-chemistry liable headgroup mimic is visible by microscopy and allows the covalent labelling of lipids. Fluorescence of the cell membranes, visible in heterogenous patches, is dependent on PCho concentration and is localised in the membrane fraction of cells, demonstrating that it is suitable for membrane labelling and cell imaging

ActS activates peptidoglycan amidases during outer membrane stress in <i>Escherichia coli</i>

The integrity of the cell envelope of E. coli relies on the concerted activity of multi-protein machineries that synthesize the peptidoglycan (PG) and the outer membrane (OM). Our previous work found that the depletion of lipopolysaccharide (LPS) export to the OM induces an essential PG remodeling process involving LD-transpeptidases (LDTs), the glycosyltransferase function of PBP1B and the carboxypeptidase PBP6a. Consequently, cells with defective OM biogenesis lyse if they lack any of these PG enzymes. Here we report that the morphological defects, and lysis associated with a ldtF mutant with impaired LPS transport, are alleviated by the loss of the predicted OM-anchored lipoprotein ActS (formerly YgeR). We show that ActS is an inactive member of LytM-type peptidoglycan endopeptidases due to a degenerated catalytic domain. ActS is capable of activating all three main periplasmic peptidoglycan amidases, AmiA, AmiB, and AmiC, which were previously reported to be activated only by EnvC and/or NlpD. Our data also suggest that in vivo ActS preferentially activates AmiC and that its function is linked to cell envelope stress

Діагностична значимість полярізаційно-оптичних властивостей рогівки ока при патології внутрішньоочного тиску

Незважаючи на прогрес в методах лікування і діагностики, глаукома останніми роками стала головною причиною невиліковної сліпоти в розвинених країнах світу. За даними ВООЗ більше 67 млн. чоловік в світі хворіють на глаукому і до 2030 року ця цифра повинна подвоїтися. Підвищення внутрішньоочного тиску (ВОТ) є одною з основних клінічних ознак глаукомного процесу, реєстрація якого лежить в основі діагностики і вибору методу адекватного лікування. Практично всі існуючи в теперішній час методи виміру ВОТ засновані на різних впливах на око (вантажами, плунжерами або струменем повітря). Як було встановлено, результати таких вимірів ВОТ суттєво залежать від біомеханічних параметрів рогівки або ока

Wettability and Bactericidal Properties of Bioinspired ZnO Nanopillar Surfaces

Nanomaterials of zinc oxide (ZnO) exhibit antibacterial activities under ambient illumination that result in cell membrane permeability and disorganization, representing an important opportunity for health-related applications. However, the development of antibiofouling surfaces incorporating ZnO nanomaterials has remained limited. In this work, we fabricate superhydrophobic surfaces based on ZnO nanopillars. Water droplets on these superhydrophobic surfaces exhibit small contact angle hysteresis (within 2-3°) and a minimal tilting angle of 1°. Further, falling droplets bounce off when impacting the superhydrophobic ZnO surfaces with a range of Weber numbers (8-46), demonstrating that the surface facilitates a robust Cassie-Baxter wetting state. In addition, the antibiofouling efficacy of the surfaces has been established against model pathogenic Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli). No viable colonies of E. coli were recoverable on the superhydrophobic surfaces of ZnO nanopillars incubated with cultured bacterial solutions for 18 h. Further, our tests demonstrate a substantial reduction in the quantity of S. aureus that attached to the superhydrophobic ZnO nanopillars. Thus, the superhydrophobic ZnO surfaces offer a viable design of antibiofouling materials that do not require additional UV illumination or antimicrobial agents.</p

A dynamic network of proteins facilitate cell envelope biogenesis in gram-negative bacteria

Bacteria must maintain the ability to modify and repair the peptidoglycan layer without jeopardising its essential functions in cell shape, cellular integrity and intermolecular interactions. A range of new experimental techniques is bringing an advanced understanding of how bacteria regulate and achieve peptidoglycan synthesis, particularly in respect of the central role played by complexes of Sporulation, Elongation or Division (SEDs) and class B penicillin-binding proteins required for cell division, growth and shape. In this review we highlight relationships implicated by a bioinformatic approach between the outer membrane, cytoskeletal components, periplasmic control proteins, and cell elongation/division proteins to provide further perspective on the interactions of these cell division, growth and shape complexes. We detail the network of protein interactions that assist in the formation of peptidoglycan and highlight the increasingly dynamic and connected set of protein machinery and macrostructures that assist in creating the cell envelope layers in Gram-negative bacteria

LI-Detector:a Method for Curating Ordered Gene-Replacement Libraries

In recent years the availability of genome sequence information has grown logarithmically resulting in the identification of a plethora of uncharacterized genes. To address this gap in functional annotation, many high-throughput screens have been devised to uncover novel gene functions. Gene-replacement libraries are one such tool that can be screened in a high-throughput way to link genotype and phenotype and are key community resources. However, for a phenotype to be attributed to a specific gene, there needs to be confidence in the genotype. Construction of large libraries can be laborious and occasionally errors will arise. Here, we present a rapid and accurate method for the validation of any ordered library where a gene has been replaced or disrupted by a uniform linear insertion (LI). We applied our method (LI-detector) to the well-known Keio library of Escherichia coli gene-deletion mutants. Our method identified 3,718 constructed mutants out of a total of 3,728 confirmed isolates, with a success rate of 99.7% for identifying the correct kanamycin cassette position. This data set provides a benchmark for the purity of the Keio mutants and a screening method for mapping the position of any linear insertion, such as an antibiotic resistance cassette in any ordered library. IMPORTANCE The construction of ordered gene replacement libraries requires significant investment of time and resources to create a valuable community resource. During construction, technical errors may result in a limited number of incorrect mutants being made. Such mutants may confound the output of subsequent experiments. Here, using the remarkable E. coli Keio knockout library, we describe a method to rapidly validate the construction of every mutant.</p