Intra-annual density fluctuations in tree rings are proxies of air temperature across Europe.

Intra-Annual Density Fluctuations (IADFs) are an important wood functional trait that determine trees' ability to adapt to climatic changes. Here, we use a large tree-ring database of 11 species from 89 sites across eight European countries, covering a climatic gradient from the Mediterranean to northern Europe, to analyze how climate variations drive IADF formation. We found that IADF occurrence increases nonlinearly with ring width in both gymnosperms and angiosperms and decreases with altitude and age. Recently recorded higher mean annual temperatures facilitate the formation of IADFs in almost all the studied species. Precipitation plays a significant role in inducing IADFs in species that exhibit drought tolerance capability, and a growth pattern known as bimodal growth. Our findings suggest that species with bimodal growth patterns growing in western and southern Europe will form IADFs more frequently, as an adaptation to increasing temperatures and droughts.

Probiotic Properties of Alcaligenes faecalis Isolated from Argyrosomus regius in Experimental Peritonitis (Rat Model).

A strain of Alcaligenes faecalis A12C (A. faecalis A12C) isolated from Argyrosomus regius is a probiotic in fish. Previous experiments showed that A. faecalis A12C had inhibitory effects on the growth of multidrug-resistant bacteria. We aimed to confirm whether A. faecalis A12C is safe and has adequate intestinal colonization in experimental rats, and evaluate its efficacy in an animal model of peritonitis. We used 30 male rats, randomly divided into 6 groups (n = 5): three groups (HA7, HA15, HA30) received A. faecalis A12C in drinking water (6 × 108 CFU/mL) for 7 days, and three control groups received drinking water only. All groups were evaluated at 7, 15, and 30 days. Survival after A. faecalis A12C administration was 100% in all groups. Mild eosinophilia (1.5%, p < 0.01) and increased aspartate aminotransferase (86 IU/L, p < 0.05) were observed in HA7, followed by progressive normalization. No histological signs of organ injury were found. We observed significant E. coli decline in faeces, parallel to an increase in A. faecalis A12C at 7 days. E. coli had a tendency to recover initial values, while A. faecalis A12C disappeared from the intestinal microbiota at 30 days. To evaluate its efficacy against peritonitis, we studied two additional groups of animals: IA group pretreated with A. faecalis A12C before E. coli intra-abdominal inoculation, and IC group inoculated with no A. faecalis A12C. We found an increase in C-reactive protein, alanine aminotransferase, urea, and eosinophils in IC animals when compared with IA. Peritonitis was more evident in IC than in IA animals. Our findings suggest that A. faecalis A12C altered clinically relevant parameters in sepsis and was associated with a lesser spread of infection.

Phase-field model for the morphology of monolayer lipid domains.

Phase-separated domains exist in multicomponent lipid monolayers and bilayers. We present here a phase-field model that takes into account the competition between lipid dipole-dipole interactions and line tension to define the domain morphology. A dynamic equation for the phase-field is solved numerically showing stationary non-circular shapes like starfish shapes. This phase-field model could be applied to study the dynamic properties of complex problems like phase segregation in pulmonary surfactant membranes and films.

Constricting force of filamentary protein rings evaluated from experimental results.

We present a model of Z -ring constriction in bacteria based on different experimental in vitro results. The forces produced by the Z ring due to lateral attraction of its constituent parts, estimated in previous studies that were based on FtsZ filaments observed by atomic force microscopy, are in good agreement with an estimation of the force required for recently found deformations in liposomes caused by FtsZ. These forces are calculated within the usual Helfrich energy formalism. In this context, we also explain the apparent attraction of multiple Z rings in the liposomes initially separated by small distances, as well as the stable distribution of rings separated by distances greater than approximately twice the diameter of the cylindrical liposomes. We adapted the model to the in vivo conditions imposed by the bacterial cell wall, concluding that the proposed mechanism gives a qualitative explanation for the force generation during bacterial division.

Modeling morphological instabilities in lipid membranes with anchored amphiphilic polymers.

Anchoring molecules, like amphiphilic polymers, are able to dynamically regulate membrane morphology. Such molecules insert their hydrophobic groups into the bilayer, generating a local membrane curvature. In order to minimize the elastic energy penalty, a dynamic shape instability may occur, as in the case of the curvature-driven pearling instability or the polymer-induced tubulation of lipid vesicles. We review recent works on modeling of such instabilities by means of a mesoscopic dynamic model of the phase-field kind, which take into account the bending energy of lipid bilayers.

Polymer-induced tubulation in lipid vesicles.

A mechanism of extraction of tubular membranes from a lipid vesicle is presented. A concentration gradient of anchoring amphiphilic polymers generates tubes from budlike vesicle protrusions. We explain this mechanism in the framework of the Canham-Helfrich model. The energy profile is analytically calculated and a tube with a fixed length, corresponding to an energy minimum, is obtained in a certain regime of parameters. Further, using a phase-field model, we corroborate these results numerically. We obtain the growth of tubes when a polymer source is added, and the budlike shape after removal of the polymer source, in accordance with recent experimental results.

[Phenotypes and genetic mechanisms of resistance to macrolides and lincosamides in viridans group streptococci]. / Fenotipos y mecanismos genéticos de resistencia a macrólidos y lincosamidas en estreptococos del grupo viridans.

Viridans group streptococci (VGS) are part of the oropharyngeal, intestinal and genital flora, but they may cause endocarditis and bacteremia in susceptible patients. Penicillin- and macrolide-resistant strains are increasing every year. The aim of this study was to investigate genetic mechanisms of resistance to macrolides in clinically relevant isolates. We identified 85 isolates from January 2004 to June 2006. Susceptibility to penicillin, cefotaxime, erythromycin, clindamycin and gentamycin was determined. A resistance phenotype was assigned according to the disk approximation test (erythromycin-clindamycin). The mechanism of resistance was determined by PCR for the following genes: ermB, ermA, ermC, ermA (TR) and mefA/E. We identified 51 isolates belonging to Streptococcus anginosus species, most of which were obtained from abdominal abscesses, and 34 isolates belonging to other species, most of which were obtained from blood cultures. The macrolide resistance rate was 28.2% (24/85). The MLS(B) phenotype was observed in 66.7% of the isolates, primarily in the S. anginosus group. The M phenotype was predominant in S. mitis and S. oralis. Isolates that expressed the constitutive MLS(B) phenotype carried the ermB gene, and those that expressed the inducible MLSB phenotype carried the ermA gene. Isolates that expressed the M phenotype carried the mefA/E gene. There was coresistance with penicillin in 20.8% (5/24) of the isolates. Coresistance with penicillin was low. These results suggest that screening for macrolide resistance in VGS would be desirable because of the potential transmission of resistance genes to other pathogenic streptococci.

Model for curvature-driven pearling instability in membranes.

A phase-field model for dealing with dynamic instabilities in membranes is presented. We use it to study curvature-driven pearling instability in vesicles induced by the anchorage of amphiphilic polymers on the membrane. Within this model, we obtain the morphological changes reported in recent experiments. The formation of a homogeneous pearled structure is achieved by consequent pearling of an initial cylindrical tube from the tip. For high enough concentration of anchors, we show theoretically that the homogeneous pearled shape is energetically less favorable than an inhomogeneous one, with a large sphere connected to an array of smaller spheres.

Fenotipos y mecanismos genéticos de resistencia a macrólidos y lincosamidas en estreptococos del grupo viridans / Phenotypes and genetic mechanisms of resistance to macrolides and lincosamides in viridans group streptococci

Los estreptococos del grupo viridans forman parte de la flora orofaríngea, intestinal y genital, pero pueden causar endocarditis y bacteriemia en pacientes susceptibles. Cada vez se describen más cepas resistentes a las penicilinas y a los macrólidos. El objetivo de nuestro estudio fue conocer los mecanismos de resistencia a los macrólidos en aislamientos con significación clínica. De enero de 2004 a junio de 2006 se identificaron 85 cepas de estreptococos del grupo viridans. Se determinó la sensibilidad a penicilina, cefotaxima, eritromicina, clindamicina y gentamicina. Se estableció el fenotipo de resistencia a los macrólidos mediante aproximación de discos (eritromicina-clindamicina). Se detectó el mecanismo genético de resistencia mediante PCR para los genes ermB, ermA, ermC, ermA (TR) y mefA/E. Se identificaron 51 cepas pertenecientes a especies del grupo anginosus, obtenidas mayoritariamente de abscesos abdominales, y 34 cepas de otras especies, obtenidas mayoritariamente de hemocultivos. La tasa de resistencia a los macrólidos fue del 28,2% (24/85). El fenotipo MLSB se observó en el 66,7% de las cepas, principalmente del grupo anginosus. El fenotipo M predominó en S. mitis y S. oralis. En las cepas con fenotipo MLSB constitutivo se detectó el gen ermB, mientras que en las cepas con expresión inducible se detectó el gen ermA. En las cepas con fenotipo M se detectó el gen mefA/E. Se observó corresistencia con penicilina en el 20,8% (5/24) de las cepas. La resistencia a los macrólidos en los estreptococos del grupo viridans es ligeramente menor que la observada en otros estudios. Destacamos mayor resistencia y presencia del fenotipo MLSB en cepas del grupo anginosus, y del fenotipo M en las restantes especies, lo cual podría estar relacionado con el origen anatómico de las cepas. La corresistencia a la penicilina fue baja. Sería recomendable vigilar periódicamente la resistencia a los macrólidos en los estreptococos del grupo viridans, posibles transmisores de resistencia a otras especies de estreptococos patógenos

Viridans group streptococci (VGS) are part of the oropharyngeal, intestinal and genital flora, but they may cause endocarditis and bacteremia in susceptible patients. Penicillin- and macrolide-resistant strains are increasing every year. The aim of this study was to investigate genetic mechanisms of resistance to macrolides in clinically relevant isolates. We identified 85 isolates from January 2004 to June 2006. Susceptibility to penicillin, cefotaxime, erythromycin, clindamycin and gentamycin was determined. A resistance phenotype was assigned according to the disk approximation test (erythromycin-clindamycin). The mechanism of resistance was determined by PCR for the following genes: ermB, ermA, ermC, ermA (TR) and mefA/E. We identified 51 isolates belonging to Streptococcus anginosus species, most of which were obtained from abdominal abscesses, and 34 isolates belonging to other species, most of which were obtained from blood cultures. The macrolide resistance rate was 28.2% (24/85). The MLSB phenotype was observed in 66.7% of the isolates, primarily in the S. anginosus group. The M phenotype was predominant in S. mitis and S. oralis. Isolates that expressed the constitutive MLSB phenotype carried the ermB gene, and those that expressed the inducible MLSB phenotype carried the ermA gene. Isolates that expressed the M phenotype carried the mefA/E gene. There was coresistance with penicillin in 20.8% (5/24) of the isolates. Coresistance with penicillin was low. These results suggest that screening for macrolide resistance in VGS would be desirable because of the potential transmission of resistance genes to other pathogenic streptococci

Dynamic model and stationary shapes of fluid vesicles.

A phase-field model that takes into account the bending energy of fluid vesicles is presented. The Canham-Helfrich model is derived in the sharp-interface limit. A dynamic equation for the phase-field has been solved numerically to find stationary shapes of vesicles with different topologies and the dynamic evolution towards them. The results are in agreement with those found by minimization of the Canham-Helfrich free energy. This fact shows that our phase-field model could be applied to more complex problems of instabilities.