Isolation and characterization from solar salterns of North Algeria of a haloarchaeon producing a new halocin

Halophilic archaea, thriving in hypersaline environments, synthesize antimicrobial substances with an unknown role, called halocins. It has been suggested that halocin production gives transient competitive advantages to the producer strains and represents one of the environmental factors influencing the microbial community composition. Herein, we report on the antibacterial activity of a new haloarchaeon selected from solar salterns of the northern coast of Algeria. A total of 81 halophilic strains, isolated from the microbial consortia, were screened for the production of antimicrobial compounds by interspecies competition test and against a collection of commercial haloarchaea. On the basis of the partial 16S rRNA sequencing, the most efficient halocin producer was recognized as belonging to Haloferax (Hfx) sp., while the best indicator microorganism, showing high sensitivity toward halocin, was related to Haloarcula genus. The main morphological, physiological and biochemical properties of Hfx were investigated and a partial purification of the produced halocin was allowed to identify it as a surface membrane protein with a molecular mass between 30 and 40 kDa. Therefore, in this study, we isolated a new strain belonging to Haloferax genus and producing a promising antimicrobial compound useful for applications in health and food industries.

     

High-throughput evaluation of the critical micelle concentration of detergents

Determination of the critical micelle concentration (CMC) value of detergents routinely used in biological applications is necessary to follow possible changes due to different buffer compositions (e.g., temperature, pH) such as those in solutions that are used for protein activity assays or crystallization. Here we report a method to determine the CMC values of detergents through a fast and robust assay that relies on the fluorescence of Hoechst 33342 using a 96-well plate reader. Furthermore, this assay provides the possibility and sensitivity to measure the CMC of detergent mixtures. The examples described here emphasize the potential and applicability of this assay and demonstrate that analysis of the physicochemical parameters of detergents can now be investigated in virtually every laboratory.     

Predictive Value of S100-B and Copeptin for Outcomes following Seizure: The BISTRO International Cohort Study

Objective

To evaluate the performance of S100-B protein and copeptin, in addition to clinical variables, in predicting outcomes of patients attending the emergency department (ED) following a seizure.

Methods

We prospectively included adult patients presented with an acute seizure, in four EDs in France and the United Kingdom. Participants were followed up for 28 days. The primary endpoint was a composite of seizure recurrence, all-cause mortality, hospitalization or rehospitalisation, or return visit in the ED within seven days.

Results

Among the 389 participants included in the analysis, 156 (40%) experienced the primary endpoint within seven days and 195 (54%) at 28 days. Mean levels of both S100-B (0.11 μg/l [95% CI 0.07–0.20] vs 0.09 μg/l [0.07–0.14]) and copeptin (23 pmol/l [9–104] vs 17 pmol/l [8–43]) were higher in participants meeting the primary endpoint. However, both biomarkers were poorly predictive of the primary outcome with a respective area under the receiving operator characteristic curve of 0.57 [0.51–0.64] and 0.59 [0.54–0.64]. Multivariable logistic regression analysis identified higher age (odds ratio [OR] 1.3 per decade [1.1–1.5]), provoked seizure (OR 4.93 [2.5–9.8]), complex partial seizure (OR 4.09 [1.8–9.1]) and first seizure (OR 1.83 [1.1–3.0]) as independent predictors of the primary outcome. A second regression analysis including the biomarkers showed no additional predictive benefit (S100-B OR 3.89 [0.80–18.9] copeptin OR 1 [1.00–1.00]).

Conclusion

The plasma biomarkers S100-B and copeptin did not improve prediction of poor outcome following seizure. Higher age, a first seizure, a provoked seizure and a partial complex seizure are independently associated with adverse outcomes.     

A new family of structurally conserved fungal effectors displays epistatic interactions with plant resistance proteins

Recognition of a pathogen avirulence (AVR) effector protein by a cognate plant resistance (R) protein triggers a set of immune responses that render the plant resistant. Pathogens can escape this so-called Effector-Triggered Immunity (ETI) by different mechanisms including the deletion or loss-of-function mutation of the AVR gene, the incorporation of point mutations that allow recognition to be evaded while maintaining virulence function, and the acquisition of new effectors that suppress AVR recognition. The Dothideomycete Leptosphaeria maculans, causal agent of oilseed rape stem canker, is one of the few fungal pathogens where suppression of ETI by an AVR effector has been demonstrated. Indeed, AvrLm4-7 suppresses Rlm3- and Rlm9-mediated resistance triggered by AvrLm3 and AvrLm5-9, respectively. The presence of AvrLm4-7 does not impede AvrLm3 and AvrLm5-9 expression, and the three AVR proteins do not appear to physically interact. To decipher the epistatic interaction between these L. maculans AVR effectors, we determined the crystal structure of AvrLm5-9 and obtained a 3D model of AvrLm3, based on the crystal structure of Ecp11-1, a homologous AVR effector candidate from Fulvia fulva. Despite a lack of sequence similarity, AvrLm5-9 and AvrLm3 are structural analogues of AvrLm4-7 (structure previously characterized). Structure-informed sequence database searches identified a larger number of putative structural analogues among L. maculans effector candidates, including the AVR effector AvrLmS-Lep2, all produced during the early stages of oilseed rape infection, as well as among effector candidates from other phytopathogenic fungi. These structural analogues are named LARS (for Leptosphaeria AviRulence and Suppressing) effectors. Remarkably, transformants of L. maculans expressing one of these structural analogues, Ecp11-1, triggered oilseed rape immunity in several genotypes carrying Rlm3. Furthermore, this resistance could be suppressed by AvrLm4-7. These results suggest that Ecp11-1 shares a common activity with AvrLm3 within the host plant which is detected by Rlm3, or that the Ecp11-1 structure is sufficiently close to that of AvrLm3 to be recognized by Rlm3.     

Influence of detergents on the activity of the ABC transporter LmrA

The ABC transporter LmrA from Lactococcus lactis has been intensively studied and a role in multidrug resistance was proposed. Here, we performed a comprehensive detergent screen to analyze the impact of detergents for a successful solubilization, purification and retention of functional properties of this ABC transporter. Our screen revealed the preference of LmrA for zwitterionic detergents. In detergent solution, LmrA purified with FC-16 was highly active with respect to ATPase activity, which could be stimulated by a substrate (rhodamine 123) of LmrA. Both, high ATPase activity and substrate stimulation were not detected for LmrA solubilized in DDM. Interestingly, reconstituted LmrA showed an opposite behavior, with a high basal ATPase activity and stimulation by rhodamine 123 for a DDM-reconstituted, but only low ATPase activity and no substrate stimulation for a FC-16 reconstituted sample.     

Molecular characterization of bacteria associated with the trophosome and the tube of Lamellibrachia sp., a siboglinid annelid from cold seeps in the eastern Mediterranean

Specimens of Lamellibrachia ( Annelida: Siboglinidae ) were recently discovered at cold seeps in the eastern Mediterranean. In this study, we have investigated the phylogeny and function of intracellular bacterial symbionts inhabiting the trophosome of specimens of Lamellibrachia sp. from the Amon mud volcano, as well as the bacterial assemblages associated with their tube. The dominant intracellular symbiont of Lamellibrachia sp. is a gammaproteobacterium closely related to other sulfide-oxidizing tubeworm symbionts. In vivo uptake experiments show that the tubeworm relies on sulfide for its metabolism, and does not utilize methane. Bacterial communities associated with the tube form biofilms and occur from the anterior to the posterior end of the tube. The diversity of 16S rRNA gene phylotypes includes representatives from the same divisions previously identified from the tube of the vent species Riftia pachyptila , and others commonly found at seeps and vents.