DNA replication proteins as potential targets for antimicrobials in drug-resistant bacterial pathogens

Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc

Numerical investigation of geogrid back-anchored sheet pile walls

peer reviewedIn the last decades, geosynthetic reinforcement has been widely used in geotech-nical applications. Recently, geogrid has also been used to back-anchor sheet pile walls. However, this system has not received sufficient attention neither in research nor in construction. Due to the complex interactions between soil, geogrid and sheet pile wall, the applicability of common design guidelines for conventionally back-anchored walls to this particular system has to be proven. To develop a fundamental understanding about the influence of various components of the system on its behaviour, numerical investigations have been conducted within this study. In this paper the influence of geogrid inclination, design of geogrid-sheet pile connection including prestressing and geogrid position on the earth pressure distribution and wall deformation is discussed. The numerical results revealed that the position of geogrid and design of geogrid-sheet pile connection significantly affect the earth pressure distribution. The wall deformations are mainly influenced by the geogrid position

Practical observations on the use of fluorescent reporter systems in Clostridioides difficile

Fluorescence microscopy is a valuable tool to study a broad variety of bacterial cell components and dynamics thereof. For Clostridioides difficile, the fluorescent proteins CFPopt, mCherry(Opt) and phiLOV2.1, and the self-labelling tags SNAP(Cd) and HaloTag, hereafter collectively referred as fluorescent systems, have been described to explore different cellular pathways. In this study, we sought to characterize previously used fluorescent systems in C. difficile cells. We performed single cell analyses using fluorescence microscopy of exponentially growing C. difficile cells harbouring different fluorescent systems, either expressing these separately in the cytosol or fused to the C-terminus of HupA, under defined conditions. We show that the intrinsic fluorescence of C. difficile cells increases during growth, independent of sigB or spo0A. However, when C. difficile cells are exposed to environmental oxygen autofluorescence is enhanced. Cytosolic overexpression of the different fluorescent systems alone, using the same expression signals, showed heterogeneous expression of the fluorescent systems. High levels of mCherry(Opt) were toxic for C. difficile cells limiting the applicability of this fluorophore as a transcriptional reporter. When fused to HupA, a C. difficile histone-like protein, the fluorescent systems behaved similarly and did not affect the HupA overproduction phenotype. The present study compares several commonly used fluorescent systems for application as transcriptional or translational reporters in microscopy and summarizes the limitations and key challenges for live-cell imaging of C. difficile. Due to independence of molecular oxygen and fluorescent signal, SNAP(Cd) appears the most suitable candidate for live-cell imaging in C. difficile to date.Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc

Practical observations on the use of fluorescent reporter systems in Clostridioides difficile

Fluorescence microscopy is a valuable tool to study a broad variety of bacterial cell components and dynamics thereof. For Clostridioides difficile, the fluorescent proteins CFPopt, mCherry(Opt) and phiLOV2.1, and the self-labelling tags SNAP(Cd) and HaloTag, hereafter collectively referred as fluorescent systems, have been described to explore different cellular pathways. In this study, we sought to characterize previously used fluorescent systems in C. difficile cells. We performed single cell analyses using fluorescence microscopy of exponentially growing C. difficile cells harbouring different fluorescent systems, either expressing these separately in the cytosol or fused to the C-terminus of HupA, under defined conditions. We show that the intrinsic fluorescence of C. difficile cells increases during growth, independent of sigB or spo0A. However, when C. difficile cells are exposed to environmental oxygen autofluorescence is enhanced. Cytosolic overexpression of the different fluorescent systems alone, using the same expression signals, showed heterogeneous expression of the fluorescent systems. High levels of mCherry(Opt) were toxic for C. difficile cells limiting the applicability of this fluorophore as a transcriptional reporter. When fused to HupA, a C. difficile histone-like protein, the fluorescent systems behaved similarly and did not affect the HupA overproduction phenotype. The present study compares several commonly used fluorescent systems for application as transcriptional or translational reporters in microscopy and summarizes the limitations and key challenges for live-cell imaging of C. difficile. Due to independence of molecular oxygen and fluorescent signal, SNAP(Cd) appears the most suitable candidate for live-cell imaging in C. difficile to date

Geogrid-Anchored sheet pile walls; A small-scale experimental and numerical study

The use of geogrids to anchor Sheet Pile Walls (SPW) is relatively new. A series of small-scale tests was performed to investigate the behaviour of geogrid-Anchored SPWs subjected to strip footing surcharge loading. Particle Image Velocimetry (PIV) techniques were used to measure soil displacement and analyse the global failure mechanism and dominant soil-geogrid interaction mechanisms. One of the tests was duplicated in a test box that was eight times as wide, showing that the influence of the small width of the test box was acceptably small. A 2D finite element model (PLAXIS) was used to simulate the tests and there was a reasonable match with the test results. The position of the strip footing load, and the length and number of the geogrid anchors, proved to be key factors in determining the bearing capacity. The results provide new insights into the stabilising effect and the effective length of the geogrid anchors, in other words the length along which geogrid-soil friction is mobilised. Contrary to the Dutch design guidelines for reinforced soil walls and conventionally anchored sheet pile walls, the results showed that the geogrid provides resistance in the active zone under the strip footing surcharge loading. </p