A Homolog of Bacillus subtilis Trigger Factor in Listeria monocytogenes Is Involved in Stress Tolerance and Bacterial Virulence

Molecular chaperones play an essential role in the folding of nascent chain polypeptides, as well as in the refolding and degradation of misfolded or aggregated proteins. They also assist in protein translocation and participate in stress functions. We identified a gene, designated tig, encoding a protein homologous to trigger factor (TF), a cytosolic ribosome-associated chaperone, in the genome of Listeria monocytogenes. We constructed a chromosomal Δtig deletion and evaluated the impact of the mutation on bacterial growth in broth under various stress conditions and on pathogenesis. The Δtig deletion did not affect cell viability but impaired survival in the presence of heat and ethanol stresses. We also identified the ffh gene, encoding a protein homologous to the SRP54 eukaryotic component of the signal recognition particle. However, a Δffh deletion was not tolerated, suggesting that Ffh is essential, as it is in Bacillus subtilis and Escherichia coli. Thus, although dispensable for growth, TF is involved in the stress response of L. monocytogenes. The Δtig mutant showed no or very modest intracellular survival defects in eukaryotic cells. However, in vivo it showed a reduced capacity to persist in the spleens and livers of infected mice, revealing that TF has a role in the pathogenicity of L. monocytogenes.     

Invading parasites: spillover of an alien nematode reduces survival in a native species

Biological Invasions - It is widely assumed that spillover of alien parasites to native host species severely impacts naïve populations, ultimately conferring a competitive advantage to...     

Fruit and vegetable and fried food consumption and 3-(2-deoxy-β-D-erythro-pentafuranosyl)pyrimido[1,2-α] purin-10(3H)-one deoxyguanosine adduct formation

Diet has been shown to modulate M(1)dG adduct, a biomarker of oxidative stress and lipid peroxidation. Thus, we analysed the association between diet and M(1)dG in 120 controls and 67 Map Ta Phut industrial estate workers in Rayong, Thailand, to evaluate the influence of fruit and vegetables, and fried and charcoal-grilled/barbecued food consumption on M(1)dG. M(1)dG was decreased in controls reporting to consume 14-17 servings/week of fruit and vegetables (mean ratio [MR]= 0.35, CI 0.18-0.69, p< 0.05). Conversely, a non-statistically significant M(1)dG increment was detected in controls consuming 9-18 servings/week of fried food (MR = 1.33, CI 0.88-2.00, p = 0.168). No effect of charcoal-grilled/barbecued food was found. No effect of diet was observed in workers. An association with smoking was observed in controls (MR = 1.88, CI 1.14-3.10, p < 0.05), but not in workers. M(1)dG can induce mutations and/or methylation changes within the promoter regions of cancer-related genes, thus promotion of healthy eating practices should be recommended.     

Votive well or refuse tip? Chronicle of an abandonment: taphonomic study of the faunal remains of an iron age well-cistern

Abstract

The well-cistern of the Iberian Fortress of Vilars (Catalonia, Spain) is a monumental feature dating to the late fifth century BCE (Vilars, phases III-IV). Management of water resources is key to interpreting the nature of the fortress, as water was essential not only for human and livestock consumption, but for irrigation, construction, and crafts. Moreover, water was integral to the site in both times of peace and war, as the structures that guaranteed provision and management coincide with facets of military architecture (moat). Yet, why was the well-cistern backfilled with animal remains and other archaeological material only a few years after its construction? To answer this and other questions, this study follows two main lines of research. Firstly, analyses were carried out on the archaeozoological remains collected inside the feature so as to interpret and characterise the nature of the assemblage. Secondly, taphonomic analyses (macro- and microscopic) were undertaken so as to reconstruct the dynamics of accumulation and the premature abandonment of the well-cistern’s primary function: supplying potable water. The results suggest that the abandonment of the well-cistern might be due in part to a drop of the groundwater level during a period of drought.     

Role of the acquisition of a type 3 secretion system in the emergence of novel pathogenic strains of Xanthomonas

Cases of emergence of novel plant-pathogenic strains are regularly reported that reduce the yields of crops and trees. However, the molecular mechanisms underlying such emergence are still poorly understood. The acquisition by environmental non-pathogenic strains of novel virulence genes by horizontal gene transfer has been suggested as a driver for the emergence of novel pathogenic strains. In this study, we tested such an hypothesis by transferring a plasmid encoding the type 3 secretion system (T3SS) and four associated type 3 secreted proteins (T3SPs) to the non-pathogenic strains of Xanthomonas CFBP 7698 and CFBP 7700, which lack genes encoding T3SS and any previously known T3SPs. The resulting strains were phenotyped on Nicotiana benthamiana using chlorophyll fluorescence imaging and image analysis. Wild-type, non-pathogenic strains induced a hypersensitive response (HR)-like necrosis, whereas strains complemented with T3SS and T3SPs suppressed this response. Such suppression depends on a functional T3SS. Amongst the T3SPs encoded on the plasmid, Hpa2, Hpa1 and, to a lesser extent, XopF1 collectively participate in suppression. Monitoring of the population sizes in planta showed that the sole acquisition of a functional T3SS by non-pathogenic strains impairs growth inside leaf tissues. These results provide functional evidence that the acquisition via horizontal gene transfer of a T3SS and four T3SPs by environmental non-pathogenic strains is not sufficient to make strains pathogenic. In the absence of a canonical effector, the sole acquisition of a T3SS seems to be counter-selective, and further acquisition of type 3 effectors is probably needed to allow the emergence of novel pathogenic strains.     

How rainfall, relative humidity and temperature influence volatile emissions from apple trees in situ

Headspace volatiles from apple-bearing twigs were collected in the field with a Radiello sampler during three different diurnal periods over the complete fruit growing season. Analyses by thermal desorption-GC-MS identified a total of 62 compounds in changing quantities, including the terpenoids alpha-pinene, camphene, beta-pinene, limonene, beta-caryophyllene and (E,E)-alpha-farnesene, the aldehydes (E)-2-hexenal, benzaldehyde and nonanal, and the alcohol (Z)-3-hexen-1-ol. The variations in emission of these plant odours were statistically related to temperature, humidity and rainfall in the field. Remarkably, rainfall had a significant positive influence on changes in volatile release during all three diurnal periods, and further factors of significance were temperature and relative humidity around noon, relative humidity in the late afternoon, and temperature and relative humidity during the night. Rainfall was associated consistently with an increase in the late afternoon in terpene and aldehyde volatiles with a known repellent effect on the codling moth, one of the key pests of apple fruit. During the summer of 2003, a season characterized by below-average rainfall, some postulated effects of drought on trees were tested by establishing correlations with rainfall. Emissions of the wood terpenes alpha-pinene, beta-pinene and limonene were negatively correlated with rainfall. Another monoterpene, camphene, was only detected in this summer but not in the previous years, and its emissions were negatively correlated with rainfall, further supporting the theory that drought can result in higher formation of secondary metabolites. Finally, the two green leaf volatiles (E)-2-hexenal and (Z)-3-hexen-1-ol were negatively correlated with rainfall, coinciding well with the expectation that water deficit stress increases activity of lipoxygenase. To our knowledge, this work represents the first empirical study concerning the influence of abiotic factors on volatile emissions from apple trees in situ.     

Maternal food calling in domestic hens: influence of feeding context

The aim of this study was to understand the relationship between production of food calls by maternal hens and food context. In a series of experiments with broody hens, we manipulated quality of items, quantity of food, food experience and dispersion of food items. We measured the frequency of food calling during standardized tests. Our results show that all the variables tested had significant effects on food calling. These results present some similarities and some discrepancies with previous reports on food calling by cockerels.     

A Simple Method for the Reconstitution of Membrane Proteins into Giant Unilamellar Vesicles

A simple method for the reconstitution of membrane protein from submicron proteoliposomes into giant unilamellar vesicles (GUVs) is presented here: This method does not require detergents, fusion peptides or a dehydration step of the membrane protein solution. In a first step, GUVs of lipids were formed by electroformation, purified and concentrated; and in a second step, the concentrated GUV solution was added to a small volume of vesicles or proteoliposomes. Material transfer from submicron vesicles and proteoliposomes to GUVs occurred spontaneously and was characterized with fluorescent microscopy and patch-clamp recordings. As a functional test, the voltage-dependent, anion-selective channel protein was reconstituted into GUVs, and its electrophysiological activity was monitored with the patch clamp. This method is versatile since it is independent of the presence of the protein, as demonstrated by the fusion of fluorescently labeled submicron vesicles and proteoliposomes with GUVs.     

Allelic diversity and phylogeny of homB, a novel co-virulence marker of Helicobacter pylori

Background  

The homB gene is a Helicobacter pylori disease-marker candidate, strongly associated with peptic ulcer disease, while homA, its paralogue gene with 90% sequence identity, is correlated with non-ulcer dyspepsia. The HomB encoded outer membrane protein was shown to contribute to the proinflammatory properties of H. pylori and also to be involved in bacterial adherence.     

Hypothesis: hyperstructures regulate initiation in Escherichia coli and other bacteria

Hyperstructures or modules have been proposed to constitute a level of organisation intermediate between macromolecules and whole cells. In this model of intracellular organisation, hyperstructures compete and collaborate for existence within the membrane and cytoplasm. Those directly involved in the cell cycle include initiation, replication and division hyperstructures based on DnaA, SeqA and the 2-minute cluster, respectively. During the run-up to initiation, the mass to DNA ratio increases and, we contend, differential gene expression leads to some hyperstructures becoming more active and stable than others. This results in a drop in the diversity of hyperstructures, some of which release DnaA as they dissociate, and a DnaA-initiation hyperstructure forms. Subsequent DNA replication and cell division generate different daughter cells containing different hyperstructures. This has the advantage of increasing the phenotypic diversity of the population. In developing this model, we also invoke hyperstructures in the partitioning of origins of replication.