The inverse autotransporters of Yersinia ruckeri,YrInv and YrIlm,contribute to biofilm formation and virulence

Yersinia ruckeri causes enteric redmouth disease (ERM) that mainly affects salmonid fishes and leads to significant economic losses in the aquaculture industry. An increasing number of outbreaks and the lack of effective vaccines against some serotypes necessitates novel measures to control ERM. Importantly, Y. ruckeri survives in the environment for long periods, presumably by forming biofilms. How the pathogen forms biofilms and which molecular factors are involved in this process, remains unclear. Yersinia ruckeri produces two surface-exposed adhesins, belonging to the inverse autotransporters (IATs), called Y. ruckeri invasin (YrInv) and Y. ruckeri invasin-like molecule (YrIlm). Here, we investigated whether YrInv and YrIlm play a role in biofilm formation and virulence. Functional assays revealed that YrInv and YrIlm promote biofilm formation on different abiotic substrates. Confocal microscopy revealed that they are involved in microcolony interaction and formation, respectively. The effect of both IATs on biofilm formation correlated with the presence of different biopolymers in the biofilm matrix, including extracellular DNA, RNA and proteins. Moreover, YrInv and YrIlm contributed to virulence in the Galleria mellonella infection model. Taken together, we propose that both IATs are possible targets for the development of novel diagnostic and preventative strategies to control ERM.     

Rainfall manipulation experiments as simulated by terrestrial biosphere models: Where do we stand?

Changes in rainfall amounts and patterns have been observed and are expected to continue in the near future with potentially significant ecological and societal consequences. Modelling vegetation responses to changes in rainfall is thus crucial to project water and carbon cycles in the future. In this study, we present the results of a new model‐data intercomparison project, where we tested the ability of 10 terrestrial biosphere models to reproduce the observed sensitivity of ecosystem productivity to rainfall changes at 10 sites across the globe, in nine of which, rainfall exclusion and/or irrigation experiments had been performed. The key results are as follows: (a) Inter‐model variation is generally large and model agreement varies with timescales. In severely water‐limited sites, models only agree on the interannual variability of evapotranspiration and to a smaller extent on gross primary productivity. In more mesic sites, model agreement for both water and carbon fluxes is typically higher on fine (daily–monthly) timescales and reduces on longer (seasonal–annual) scales. (b) Models on average overestimate the relationship between ecosystem productivity and mean rainfall amounts across sites (in space) and have a low capacity in reproducing the temporal (interannual) sensitivity of vegetation productivity to annual rainfall at a given site, even though observation uncertainty is comparable to inter‐model variability. (c) Most models reproduced the sign of the observed patterns in productivity changes in rainfall manipulation experiments but had a low capacity in reproducing the observed magnitude of productivity changes. Models better reproduced the observed productivity responses due to rainfall exclusion than addition. (d) All models attribute ecosystem productivity changes to the intensity of vegetation stress and peak leaf area, whereas the impact of the change in growing season length is negligible. The relative contribution of the peak leaf area and vegetation stress intensity was highly variable among models.     

Economic Recession and Emergence of an HIV-1 Outbreak among Drug Injectors in Athens Metropolitan Area: A Longitudinal Study

Background

During 2011, a dramatic increase (1600%) of reported HIV-1 infections among injecting drug users (IDUs) was noted in Athens, Greece. We herein assess the potential causal pathways associated with this outbreak.

Methods

Our study employed high resolution HIV-1 phylogenetic and phylogeographic analyses. We examined also longitudinal data of ecological variables such as the annual growth of gross domestic product (GDP) of Greece in association with HIV-1 and HCV sentinel prevalence in IDUs, unemployment and homelessness rates and HIV transmission networks in Athens IDUs before and during economic recession (2008–2012).

Results

IDU isolates sampled in 2011 and 2012 suggested transmission networks in 94.6% and 92.7% of the cases in striking contrast with the sporadic networking (5%) during 1998–2009. The geographic origin of most HIV-1 isolates was consistent with the recently documented migratory waves in Greece. The decline in GDP was inversely correlated with annual prevalence rates of HIV and HCV and with unemployment and homelessness rates in IDUs (all p<0.001). The slope of anti-HCV prevalence in the sentinel populations of IDUs and in “new” drug injectors was found 120 and 1.9-fold (p = 0.007, p = 0.08 respectively) higher in 2008–2012 (economic recession) compared with 2002–2006. The median (25th, 75th) size of transmission networks were 34 (12, 58) and 2 (2, 2) (p = 0.057) in 2008–2012 and 1998–2007, respectively. The coverage of harm reduction services was low throughout the study period.

Conclusions

Scaling-up harm reduction services and addressing social and structural factors related to the current economic crisis should be urgently considered in environments where HIV-1 outbreaks may occur.     

Transcriptional and epigenetic effects of Vitis vinifera L. leaf extract on UV-stressed human dermal fibroblasts

Molecular Biology Reports - Adverse environmental conditions such as UV radiation induce oxidative and aging events leading to severe damage to human skin cells. Natural products such as plant...     

Sizeable acquired subglottic cyst in a baby with Williams–Beuren syndrome: Association or coincidence?

We describe a case of an acquired subglottic cyst presented with persistent stridor and voice hoarsening in a baby diagnosed with Williams–Beuren syndrome that was born premature and required intubation during neonatal period. We also comment on whether this is a coincidence or there can be an association between impaired elastogenesis, a feature of patients with the syndrome and the formation of a subglottic cyst.     

Association of NADPH oxidase p22phox gene C242T, A640G and −930A/G polymorphisms with primary knee osteoarthritis in the Greek population

Osteoarthritis (OA) is the most common form of arthritis with still unknown pathogenic etiology and considerable contribution of genetic factors. Recently, a new emerging role of oxidative stress in the pathology of OA has been reported, lacking however elucidation of the underlying mechanism. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase being a complex enzyme produced by chondrocytes, presents the major source of reactive oxygen species and main contributor of increased oxidative stress. The present study aims to evaluate the association of NADPH oxidase p22phox gene C242T, A640G and ?A930G polymorphisms with primary knee OA in the Greek population. One hundred fifty five patients with primary symptomatic knee OA participated in the study along with 139 matched controls. Genotypes were determined using polymerase chain reaction and restriction fragment length polymorphism technique. Allelic and genotypic frequencies were compared between both study groups. NADPH p22phox ?A930G polymorphism was significantly associated with knee OA in the crude analysis (P = 0.018). No significant difference was detected for C242T and A640G polymorphisms (P > 0.05). The association between ?A930G polymorphism and knee OA disappeared when the results were adjusted for obesity (P = 0.078, odds ratio 0.54, 95 % CI 0.272–1.071). The interaction between all three polymorphisms was not significant. The present study shows that NADPH oxidase p22phox gene C242T, A640G and ?A930G polymorphisms are not risk factors for knee OA susceptibility in the Greek population. Further studies are needed to give a global view of the importance of this polymorphism in the pathogenesis of OA.     

Efficient homologous recombination with short length flanking fragments in Ku70 deficient Yarrowia lipolytica strains

In Yarrowia lipolytica, targeted gene replacement occurs only with long length (1 kb) homologous flanking fragments, as this yeast preferentially uses the non-homologous end-joining mechanism (NHEJ) for DNA repair over homologous recombination (HR). To improve the frequency of HR, we identified and disrupted the KU70 and KU80 genes responsible for double strand break repair in the NHEJ pathway in Y. lipolytica. In ku70? HR of URA3 marker at the ADE2 locus occurred with 43 % frequency with as little as 50 bp long flanking regions. The number of Ura⁺ transformants was reduced to 1 % of the Po1d (ura3-302) wild type-like strain level, regardless of the flanking fragment length. On the contrary, even though HR was not improved in ku80?, Ura⁺ transformants was 60 % lower compared to the wild type.     

Diversity of Planktonic and Attached Bacterial Communities in a Phenol-Contaminated Sandstone Aquifer

Polluted aquifers contain indigenous microbial communities with the potential for in situ bioremediation. However, the effect of hydrogeochemical gradients on in situ microbial communities (especially at the plume fringe, where natural attenuation is higher) is still not clear. In this study, we used culture-independent techniques to investigate the diversity of in situ planktonic and attached bacterial communities in a phenol-contaminated sandstone aquifer. Within the upper and lower plume fringes, denaturing gradient gel electrophoresis profiles indicated that planktonic community structure was influenced by the steep hydrogeochemical gradient of the plume rather than the spatial location in the aquifer. Under the same hydrogeochemical conditions (in the lower plume fringe, 30 m below ground level), 16S rRNA gene cloning and sequencing showed that planktonic and attached bacterial communities differed markedly and that the attached community was more diverse. The 16S rRNA gene phylogeny also suggested that a phylogenetically diverse bacterial community operated at this depth (30 mbgl), with biodegradation of phenolic compounds by nitrate-reducing Azoarcus and Acidovorax strains potentially being an important process. The presence of acetogenic and sulphate-reducing bacteria only in the planktonic clone library indicates that some natural attenuation processes may occur preferentially in one of the two growth phases (attached or planktonic). Therefore, this study has provided a better understanding of the microbial ecology of this phenol-contaminated aquifer, and it highlights the need for investigating both planktonic and attached microbial communities when assessing the potential for natural attenuation in contaminated aquifers.     

Importance of the methyl-citrate cycle on glycerol metabolism in the yeast Yarrowia lipolytica

A novel approach to trigger lipid accumulation and/or citrate production in vivo through the inactivation of the 2-methyl-citrate dehydratase in Yarrowia lipolytica was developed. In nitrogen-limited cultures with biodiesel-derived glycerol utilized as substrate, the Δphd1 mutant (JMY1203) produced 57.7 g/L of total citrate, 1.6-fold more than the wild-type strain, with a concomitant glycerol to citrate yield of 0.91 g/g. Storage lipid in cells increased at the early growth stages, suggesting that inactivation of the 2-methyl-citrate dehydratase would mimic nitrogen limitation. Thus, a trial of JMY1203 strain was performed with glycerol under nitrogen-excess conditions. Compared with the equivalent nitrogen-limited culture, significant quantities of lipid (up to ∼31% w/w in dry weight, 1.6-fold higher than the nitrogen-limited experiment) were produced. Also, non-negligible quantities of citric acid (up to ∼26 g/L, though 0.57-fold lower than the nitrogen-limited experiment) were produced, despite remarkable nitrogen presence into the medium, indicating the construction of phenotype that constitutively accumulated lipid and secreted citrate in Y. lipolytica during growth on waste glycerol utilized as substrate.