Co-evolution with lytic phage selects for the mucoid phenotype of Pseudomonas fluorescens SBW25

The effects of co-evolution with lytic phage on bacterial virulence-related traits are largely unknown. In this study we investigate the incidence of the mucoid phenotype of the bacterium Pseudomonas fluorescens SBW25 in response to co-evolution with the lytic phage phi2 (φ2). The mucoid phenotype of Pseudomonas spp. is due to overproduction of alginate and is a considerable virulence factor contributing to the intractability of infections most notably in cystic fibrosis (CF) lung, but also in pathogenic infections of plants. Our data show that this phenotype can evolve as an adaptive response to phage predation and is favoured under specific abiotic conditions, in particular a homogenous spatial structure and a high rate of nutrient replacement. The mucoid phenotype remains partially sensitive to phage infection, which facilitates ‘apparent competition'' with phage-sensitive competitors, partially offsetting the costs of alginate production. Although P. fluorescens SBW25 is not a pathogen, several key characteristics typical of Pseudomonas aeruginosa clinical isolates from CF lung were noted, including loss of motility on mucoid conversion and a high rate of spontaneous reversion to the wild-type phenotype. Although the genetic mechanisms of this phenotype remain unknown, they do not include mutations at many of the commonly reported loci implicated in mucoid conversion, including mucA and algU. These data not only further our understanding of the potential role phage have in the ecology and evolution of bacteria virulence in both natural and clinical settings, but also highlight the need to consider both biotic and abiotic variables if bacteriophages are to be used therapeutically.     

Direct Observation of Surface Plasmon Polariton Propagation and Interference by Time-Resolved Imaging in Normal-Incidence Two Photon Photoemission Microscopy

Plasmonics - Time-resolved imaging of the propagation and interference of isolated ultrashort surface plasmon polariton wave packets is demonstrated using two photon photoemission microscopy. The...     

Governance of indigenous policy in the neo-liberal age: indigenous disadvantage and the intersecting of paternalism and neo-liberalism as a racial project

Thinking about the governance of Indigenous poverty as an economic, social and racial project, the paper offers a way of understanding the dynamics of Indigenous policy formation in Australia in the neo-liberal age as what Howard Winant first coined a racial formation. In providing this analysis, this paper sits alongside a small, but growing body of work that reveals the racialized effects of governing through poverty in the neo-liberal age.     

Effecten van geriatrische COPD-revalidatie op ziekenhuisopnames en inspanningstolerantie: een retrospectief observationele studie

Introduction

Frail COPD patients are frequently not accepted for regular pulmonary rehabilitation programs due to low physical condition and functional limitations. Rehabilitation programs in nursing homes for geriatric patients with COPD have been developed. The effects of such programs are largely unknown.

Aims

To assess the course of COPD-related hospital admissions and exercise tolerance in a cohort of frail COPD patients participating in geriatric COPD rehabilitation.

Methods

Retrospective observational study with a follow up of 12 months after discharge from rehabilitation. COPD related hospital admission days were measured in the year before and after participating rehabilitation. Exercise tolerance was measured by the six minute walk test (6MWT) at admission and at discharge from rehabilitation.

Results

Fifty-eight participants accomplished the rehabilitation program. Twelve patients died in the first year after discharge. The median number of hospital admission days in the year before participating rehabilitation was 21 (IQR 10–33). The first year after discharge this was decreased to a median of 6 (IQR 0–12). The 6MWT increased from 194 (SD 85) meters at admission to 274 (SD 95) meters at discharge (mean difference 80 m, SD 72; p < 0.05).

Conclusions

Geriatric COPD rehabilitation in a nursing home setting seems to reduce hospital admissions in frail COPD patients and to increase exercise tolerance.

     

Characterization of the Streptomyces lividans PspA response

Phage shock protein (Psp) is induced by extracytoplasmic stress that may reduce the energy status of the cell. It is encoded in Escherichia coli by the phage shock protein regulon consisting of pspABCDE and by pspF and pspG. The phage shock protein system is highly conserved among a large number of gram-negative bacteria. However, many bacterial genomes contain only a pspA homologue but no homologues of the other genes of the Psp system. This conservation indicates that PspA alone might play an important role in these bacteria. In Streptomyces lividans, a soil-borne gram-positive bacterium, the phage shock protein system consists only of the pspA gene. In this report, we showed that pspA encodes a 28-kDa protein that is present in both the cytoplasmic and the membrane fractions of the S. lividans mycelium. We demonstrated that the pspA gene is strongly induced under stress conditions that attack membrane integrity and that it is essential for growth and survival under most of these conditions. The data reported here clearly show that PspA plays an important role in S. lividans under stress conditions despite the absence of other psp homologues, suggesting that PspA may be more important in most bacteria than previously thought.     

Differences in cue-dependent spatial navigation may be revealed by in-depth swimming analysis

Several factors can influence allocentric navigation in the Morris water maze (MWM), including the number of available distal visual cues. Using in-depth analytical measures investigating platform-based and swimming behaviour, we examine and compare animals exposed to either one or three distal visual cues during MWM acquisition. We demonstrate that, although animals exposed to one cue can acquire the task as well as those in a multiple cue condition, several subtle differences between the groups’ swimming behaviours are noted. Both groups actively use cues to guide them to the platform, but changing the number of cues alters the animals’ patterns of behaviour, wherein exposure to a single cue leads to a simpler strategy in which the cue appears to act as a beacon for navigation.     

Synthetic sheep urine alters fungal community structure in an upland grassland soil

Agricultural improvement (fertilisation, liming, intensification of grazing) of acidic upland pastures results in loss of indigenous flora and notable changes in microbial community structure. Such practices have recently raised concerns regarding the possible impacts on natural ecosystem biodiversity and functioning. The effects of synthetic sheep urine (SSU) and plant species on fungal community structure in upland grassland microcosms were investigated. Plant species typical of agriculturally unimproved (Agrostis capillaris) and improved (Lolium perenne) pastures were treated with low, medium or high concentrations of SSU, with harvests carried out 10 d and 50 d after SSU application. Root biomass was negatively affected by SSU addition whereas shoot biomass did not display any significant change. Fungal richness (number of operational taxonomic units) was negatively correlated with SSU concentration (p < 0.001), and also with time (p < 0.001).Multi-dimensional scaling plots revealed significant changes in fungal community composition, depending on concentration of SSU and plant species type, while canonical correspondence analysis also emphasised the importance of interacting environmental variables. In addition, SIMPER analyses supported the finding that shifts in fungal community composition under different SSU and plant treatments had occurred. Overall, while SSU appeared to be influential in determining fungal community structure, community changes were largely driven by interacting environmental factors. This study contributes to our understanding of the potential implications of intensified farming, in particular increased pressure from grazing animals, on fungal community structure in semi-natural grassland systems.     

Murine Bioluminescent Hepatic Tumour Model

This video describes the establishment of liver metastases in a mouse model that can be subsequently analysed by bioluminescent imaging. Tumour cells are administered specifically to the liver to induce a localised liver tumour, via mobilisation of the spleen and splitting into two, leaving intact the vascular pedicle for each half of the spleen. Lewis lung carcinoma cells that constitutively express the firefly luciferase gene (luc1) are inoculated into one hemi-spleen which is then resected 10 minutes later. The other hemi-spleen is left intact and returned to the abdomen. Liver tumour growth can be monitored by bioluminescence imaging using the IVIS whole body imaging system. Quantitative imaging of tumour growth using IVIS provides precise quantitation of viable tumour cells. Tumour cell death and necrosis due to drug treatment is indicated early by a reduction in the bioluminescent signal. This mouse model allows for investigating the mechanisms underlying metastatic tumour-cell survival and growth and can be used for the evaluation of therapeutics of liver metastasis. Download video file.^{(57M, mp4)}