Unraveling Azospirillum's colonization ability through microbiological and molecular evidence.

It is known that members of the bacterial genus Azospirillum can promote the growth of a great variety of plants, an ability harnessed by the industry to create bioproducts aimed to enhance the yield of economically relevant crops. Its versatile metabolism allows this bacterium to adapt to numerous environments, from optimal to extreme or highly polluted. The fact of having been isolated from soil and rhizosphere samples collected worldwide and many other habitats proves its remarkable ubiquity. Azospirillum rhizospheric and endophytic lifestyles are governed by several mechanisms, leading to efficient niche colonization. These mechanisms include cell aggregation and biofilm formation, motility, chemotaxis, phytohormone and other signaling molecules production, and cell-to-cell communication, in turn, involved in regulating Azospirillum interactions with the surrounding microbial community. Despite being infrequently mentioned in metagenomics studies after its introduction as an inoculant, an increasing number of studies detected Azospirillum through molecular tools (mostly 16S rRNA sequencing) as part of diverse, even unexpected, microbiomes. This review focuses on Azospirillum traceability and the performance of the available methods, both classical and molecular. An overview of Azospirillum occurrence in diverse microbiomes and the less-known features explaining its notorious ability to colonize niches and prevail in multiple environments is provided.

Day and blue light modify growth, cell physiology and indole-3-acetic acid production of Azospirillum brasilense Az39 under planktonic growth conditions.

AIM: In this work, we evaluated the effects of light on growth, cell physiology and stress response of Azospirillum brasilense Az39, a non-photosynthetic rhizobacteria, under planktonic growth conditions. METHODS AND RESULTS: Exponential cultures of Az39 were exposed to blue (BL), red (RL) and daylight (DL) or maintained in darkness for 24, 48 and 72 h. The biomass production and indole 3-acetic acid (IAA) biosynthesis increased by exposition to DL. Conversely, BL decreased IAA concentration through a direct effect on the molecule. The DL increased superoxide dismutase activity, hydrogen peroxide and thiobarbituric acid reactive substances levels, but the last one was also increased by BL. Both DL and BL increased cell aggregation but only BL increased biofilm formation. CONCLUSIONS: We demonstrated that both BL and DL are stress effectors for A. brasilense Az39 under planktonic growth conditions. The DL increased biomass production, IAA biosynthesis and bacterial response to stress, whereas BL induced cell aggregation and biofilms formation, but decreased the IAA concentration by photooxidation. SIGNIFICANCE AND IMPACT OF THE STUDY: Blue light and DL changes growth capacity, cell physiology and plant growth promotion ability of A. brasilense Az39 and these changes could be considered to improve the production and functionality of biofertilizers.

Azospirillum brasilense Az39, a model rhizobacterium with AHL quorum-quenching capacity.

AIMS: The aim of this research was to analyse the quorum-sensing (QS) and quorum-quenching (QQ) mechanisms based on N-acyl-l-homoserine lactones (AHLs) in Azospirillum brasilense Az39, a strain with remarkable capacity to benefit a wide range of crops under agronomic conditions. METHODS AND RESULTS: We performed an in silico and in vitro analysis of the quorum mechanisms in A. brasilense Az39. The results obtained in vitro using the reporter strains Chromobacterium violaceum and Agrobacterium tumefaciens and liquid chromatography coupled with mass-mass spectrometry analysis showed that although Az39 does not produce AHL molecules, it is capable of degrading them by at least two hypothetical enzymes identified by bioinformatics approach, associated with the bacterial cell. In Az39 cultures supplemented with 500 nmol l-1 of the C3 unsubstituted AHLs (C4, C6, C8, C10, C12, C14), AHL levels were lower than in noninoculated LB media controls. Similar results were observed upon the addition of AHLs with hydroxy (OH-) and keto (oxo-) substitutions in C3. These results not only demonstrate the ability of Az39 to degrade AHLs. They also show the wide spectrum of molecules that can be degraded by this bacterium. CONCLUSIONS: Although A. brasilense Az39 is a silent bacterium unable to produce AHL signals, it is able to interrupt the communications between other bacteria and/or plants by a QQ activity. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report confirming by unequivocal methodology the ability of A. brasilense, one of the most agriculturally used benefic bacteria around the world, to degrade AHLs by a QQ mechanism.

Clinical comparison between simple laminectomy and laminectomy plus posterior instrumentation in surgical treatment of cervical myelopathy.

BACKGROUND: Posterior stabilization in patients treated with laminectomy for spondylotic cervical myelopathy is still a debate. Despite both being reported in literature by several authors, some controversies still exist. The aim of this study is to compare clinical and radiological outcomes in patients treated with laminectomy or laminectomy with posterior stabilization. MATERIAL AND METHODS: We retrospectively evaluated 42 patients affected by cervical myelopathy (mean age 70.43 ± 5.03 years), 19 treated with laminectomy (group A) and 23 with laminectomy and posterior instrumentation (group B). Neurological status was assessed with Nurick scale, pain with VAS and radiological parameters with C2-C7 SVA, T1 slope and C2-C7 lordosis, clinical function with modified Japanese Orthopaedic Association score (JOA). Also, surgery time and blood loss were recorded. Student's t test was used for continuous variables, while Kruskal-Wallis test was used for categorical values. RESULTS: No differences were found in postoperative Nurick scale (p = 0.587), VAS (p = 0.62), mJOA (p = 0.197) and T1 slope (p = 0.559), while laminectomy with fusion showed better postoperative cervical lordosis (p = 0.007) and C2-C7 SVA (p < 0.00001), but higher blood loss (p < 0.00001) and surgical time (p < 0.00001). Both groups showed better Nurick scale (p = 0.00017 for group A and p = 0.00081 for group B), VAS (p = 0.02 for group A and p = 0.046 for group B) and mJOA (p < 0.00001 for both groups) than preoperative values. CONCLUSIONS: Both treatments are a valuable choice, offering some benefits and disadvantages against each other. Each procedure must be carefully evaluated on the basis of patients' general status, preoperative pain, signs of instability and potential benefits from cervical alignment correction.

Phenogenetic profile and agronomic contribution of Azospirillum argentinense Az39T, a reference strain for the South American inoculant industry.

Azospirillum sp. is a plant growth-promoting rhizobacteria largely recognized for its potential to increase the yield of different important crops. In this work, we present a thorough genomic and phenotypic analysis of A. argentinense Az39T to provide new insights into the beneficial mechanisms of this microorganism. Phenotypic analyses revealed the following in vitro abilities: growth at 20-38 °C (optimum, 28 °C), pH 6.0-8.0 (optimum, pH 6.8), and in the presence of 1% (w/v) NaCl; production of variable amounts of PHB as intracellular granules; nitrogen fixation under microaerophilic conditions; IAA synthesis in the presence of L-tryptophan. Through biochemical (API 20NE) and carbon utilization profiling (Biolog) assays, we proved that A. argentinense Az39T is able to use 15 substrates and metabolize 19 different carbon substrates. Lipid composition indicated a predominance of medium and long-chain saturated fatty acids. A total of 6 replicons classified as one main chromosome, three chromids, and two plasmids, according to their tRNA and core essential genes contents, were identified. Az39T genome includes genes associated with multiple plant growth-promoting (PGP) traits such as nitrogen fixation and production of auxins, cytokinin, abscisic acid, ethylene, and polyamines. In addition, Az39T genome harbor genetic elements associated with physiological features that facilitate its survival in the soil and competence for rhizospheric colonization; this includes motility, secretion system, and quorum sensing genetic determinants. A metadata analysis of Az39T agronomic performance in the pampas region, Argentina, demonstrated significant grain yield increases in wheat and maize, proving its potential to provide better growth conditions for dryland cereals. In conclusion, our data provide a detailed insight into the metabolic profile of A. argentinense Az39T, the strain most widely used to formulate non-legume inoculants in Argentina, and allow a better understanding of the mechanisms behind its field performance.

Multiple 3D inversion recovery imaging for volume T1 mapping of the heart.

In this article, a three-dimensional inversion recovery sequence was optimized with the aim of generating in vivo volume T(1) maps of the heart using a 1.5-T MR system. Acquisitions were performed before and after gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) administration in one patient with hypertrophic cardiomyopathy and in two healthy volunteers. Data were acquired with a multishot fast field echo readout using both ECG and respiratory triggers. A dedicated phantom, composed of four solutions with different T(1) values, was positioned on the subjects' thoracic region to perform patient-specific calibration. Pixel based T(1) maps were calculated with a custom Matlab(®) code. Phantom measurements showed a good accuracy of the technique and in vivo T(1) estimation of liver, skeletal muscle, myocardium, and blood resulted in good agreement with values reported in the literature. Multiple three-dimensional inversion recovery technique is a feasible and accurate method to perform T(1) volume mapping.

Changing clinical and pathological features of gastric cancer over time.

BACKGROUND: The aim of the present multicentre observational study was to evaluate potential changes in clinical and pathological features of patients with gastric cancer (GC) treated in a 15-year interval. METHODS: A centralized prospective database including clinical, surgical, pathological and follow-up data from 2822 patients who had resection of a primary GC was analysed. The analysis focused on three periods: 1991-1995 (period 1), 1996-2000 (period 2) and 2001-2005 (period 3). Surgical procedure, pathological classification and follow-up were standardized among centres. RESULTS: The number of resections decreased from 1024 in period 1 to 955 and 843 in periods 2 and 3 respectively. More advanced stages and a smaller number of intestinal-type tumours of the distal third were observed over time. Five-year survival rates after R0 resection (2320 patients) did not change over time (overall: 56·6 and 51·2 per cent in periods 1 and 3; disease-free: 66·8 and 61·1 per cent respectively). Decreases in survival in more recent years were related particularly to more advanced stage, distal tumours and tumours in women. Multivariable analysis showed a lower probability of overall and disease-free survival in the most recent interval: hazard ratio 1·22 (95 per cent confidence interval 1·06 to 1·40) and 1·29 (1·06 to 1·58) respectively compared with period 1. Recurrent tumours were more frequently peritoneal rather than locoregional. CONCLUSION: Overall and disease-free survival rates after R0 resection of GC were unchanged over time.

Emergence of complex behavior in gelling systems starting from simple behavior of single clusters.

A theoretical and numerically study of dynamical properties in the sol-gel transition is presented. In particular, the complex phenomenology observed experimentally and numerically in gelling systems is reproduced in the framework of percolation theory, under simple assumptions on the relaxation of single clusters. By neglecting the correlation between particles belonging to different clusters, the quantities of interest (such as the self intermediate scattering function, the dynamical susceptibility, the Van-Hove function, and the non-Gaussian parameter) are written as superposition of those due to single clusters. Connection between these behaviors and the critical exponents of percolation are given. The theoretical predictions are checked in a model for permanent gels, where bonds between monomers are described by a finitely extendable nonlinear elastic potential. The data obtained in the numerical simulations are in good agreement with the analytical predictions.

Self-tuning phase separation in a model with competing interactions inspired by biological cell polarization.

We present a theoretical study of a system with competing short-range ferromagnetic attraction and a long-range antiferromagnetic repulsion, in the presence of a uniform external magnetic field. The interplay between these interactions, at sufficiently low temperature, leads to the self-tuning of the magnetization to a value which triggers phase coexistence, even in the presence of the external field. The investigation of this phenomenon is performed using a Ginzburg-Landau functional in the limit of an infinite number of order parameter components (large N model). The scalar version of the model is expected to describe the phase separation taking place on a cell surface when this is immersed in a uniform concentration of chemical stimulant. A phase diagram is obtained as a function of the external field and the intensity of the long-range repulsion. The time evolution of the order parameter and of the structure factor in a relaxation process is studied in different regions of the phase diagram.

Dynamical heterogeneity in a model for permanent gels: different behavior of dynamical susceptibilities.

We present a systematic study of dynamical heterogeneity in a model for permanent gels upon approaching the gelation threshold. We find that the fluctuations of the self-intermediate scattering function are increasing functions of time, reaching a plateau whose value, at large length scales, coincides with the mean cluster size and diverges at the percolation threshold. Another measure of dynamical heterogeneities-i.e., the fluctuations of the self-overlap-displays instead a peak and decays to zero at long times. The peak, however, also scales as the mean cluster size. Arguments are given for this difference in the long-time behavior. We also find that the non-Gaussian parameter reaches a plateau in the long-time limit. The value of the plateau of the non-Gaussian parameter, which is connected to the fluctuations of diffusivity of clusters, increases with the volume fraction and remains finite at the percolation threshold.

Columnar and lamellar phases in attractive colloidal systems.

In colloidal suspensions, at low volume fraction and temperature, dynamical arrest occurs via the growth of elongated structures that aggregate to form a connected network at gelation. Here we show that, in the region of parameter space where gelation occurs, the stable thermodynamical phase is a crystalline columnar one. Near and above the gelation threshold, the disordered spanning network slowly evolves and finally orders to form the crystalline structure. At higher volume fractions the stable phase is a lamellar one, which seems to have a still longer ordering time.

Complex viscosity behavior and cluster formation in attractive colloidal systems.

The increase in viscosity that is observed in attractive colloidal systems by varying the temperature or the volume fraction can be related to the formation of structures due to particle aggregation. In particular we have studied the nontrivial dependence of the viscosity from the temperature and the volume fraction in the copolymer-micellar system L64. The comparison of the experimental data with the results of numerical simulations in a simple model for gelation phenomena suggests that this intriguing behavior can be explained in terms of cluster formation and that this picture can be quite generally extended to other attractive colloidal systems.

Gastric GISTs: Analysis of c-Kit, PDGFRA and BRAF mutations in relation to prognosis and clinical pathological characteristics of patients - A GIRCG study.

BACKGROUND: Gastric gastrointestinal stromal tumors (GISTs) represent a subgroup of GISTs with a better prognosis than those located in other areas. In this retrospective study we performed a molecular characterization of a large series of patients with gastric GISTs in relation to clinical-pathological characteristics and prognosis. METHODS: DNA was extracted from paraffin-embedded sections from 221 gastric GIST patients submitted to surgery. Exons 9, 11, 13 and 17 of KIT, exons 12 and 18 of PDGFRA and exons 11 and 15 of BRAF were analyzed by direct sequencing. Cox regression analysis adjusted for clinical-pathological factors was performed to evaluate KIT and PDGFRA mutations in relation to the composite endpoint of relapse or death. RESULTS: KIT and PDGFRA mutations were observed in 119 (53.8%) and 56 (25.3%) patients, respectively, whereas 46 (20.8%) patients had wild type (wt) disease. Univariable analyses showed that a high Miettinen risk category and the presence of ulceration and KIT deletions were associated with increased risk of relapse or death (p < 0.001; p = 0.0389 and p = 0.002, respectively). After adjusting for Miettinen risk score, KIT deletions remained an independent prognostic factor (HRadj = 2.65, 95% CI [1.15-6.13], p = 0.023). Moreover, KIT deletions in exon 11 codons 557, 558 or 559 were associated with a higher risk of relapse or death than wt tumors (HRadj = 3.29 95% CI [1.64-6.64], p = 0.001). CONCLUSIONS: KIT deletions in exon 11, especially those involving codons 557, 558 or 559, were correlated with a more aggressive gastric GIST phenotype and increased risk of relapse or death.

Extended lymphadenectomy in elderly and/or highly co-morbid gastric cancer patients: A retrospective multicenter study.

BACKGROUND: Gastrectomy with extended lymphadenectomy is considered the gold standard treatment for advanced gastric cancer, with no age- or comorbidity-related limitations. We evaluated the safety and efficacy of curative gastrectomy with extended nodal dissection, verifying survival in elderly and highly co-morbid patients. METHODS: In a retrospective multicenter study, we examined 1322 non-metastatic gastric-cancer patients that underwent curative gastrectomy with D2 versus D1 lymphadenectomy from January 2000 to December 2009. Postoperative complications, overall survival (OS), and disease-specific survival (DSS) according to age and the Charlson Comorbidity Score were analyzed in relation to the extent of lymphadenectomy. RESULTS: Postoperative morbidity was 30.4%. Complications were more frequent in highly co-morbid elderly patients, and, although general morbidity rates after D2 and D1 lymphadenectomy were similar (29.9% and 33.2%, respectively), they increased following D2 in highly co-morbid elderly patients (39.6%). D2-lymphadenectomy significantly improved 5-year OS and DSS (48.0% vs. 37.6% in D1, p < 0.001 and 72.6% vs. 58.1% in D1, p < 0.001, respectively) in all patients. In elderly patients, this benefit was present only in 5-year DSS. D2 nodal dissection induced better 5-year OS and DSS rates in elderly patients with positive nodes (29.7% vs. 21.2% in D1, p = 0.008 and 47.5% vs. 30.6% in D1, p = 0.001, respectively), although it was present only in DSS when highly co-morbid elderly patients were considered. CONCLUSION: Extended lymphadenectomy confirmed better survival rates in gastric cancer patients. Due to high postoperative complication rate and no significant improvement of the OS, D1 lymphadenectomy should be considered in elderly and/or highly co-morbid gastric cancer patients.

Jamming transition in granular media: a mean-field approximation and numerical simulations.

In order to study analytically the nature of the jamming transition in granular material, we have considered a cavity method mean-field theory, in the framework of a statistical mechanics approach, based on Edwards' original idea. For simplicity, we have applied the theory to a lattice model, and a transition with exactly the same nature of the glass transition in mean-field models for usual glass formers is found. The model is also simulated in three dimensions under tap dynamics, and a jamming transition with glassy features is observed. In particular, two-step decays appear in the relaxation functions and dynamic heterogeneities resembling ones usually observed in glassy systems. These results confirm early speculations about the connection between the jamming transition in granular media and the glass transition in usual glass formers, giving moreover a precise interpretation of its nature.

Traumatic lesions of the diaphragm. Our experience in 33 cases and review of the literature.

We reviewed 33 consecutive patients with diaphragmatic injuries. Twenty-nine were admitted in emergency conditions after blunt (22 patients) or penetrating injury, presenting shock, dyspnoea, coma or acute abdomen in 21 cases; major associated lesions were found in 23 patients. Four patients presented acute complications of visceral herniation 2, 4, 84 and 216 months after the trauma. The diagnosis was preoperative in 23 cases, intraoperative in 9; in one case it was missed at laparotomy, becoming evident the day after. The sensibility of preoperative chest x-ray and CT was 86% and 100% in presence of visceral herniation, 14% and 0% in absence of visceral hernia. The diaphragmatic repair was always obtained by direct suture, following 20 haemostatic procedures (liver, spleen, mesenterium) and two bowel resections. The mortality rate was 24.4%; the morbidity rate was 48%. Traumatic lesions of the diaphragm are generally expression of particularly severe trauma whose outcome is mainly influenced by the associated lesions. They are also correlated to specific morbidity and mortality, so the surgical exploration is mandatory whenever this injury is suspected, considering that the preoperative diagnosis relies on visceral dislocation. Associated lesions influence the surgical strategy but a direct suture is usually effective in preventing specific complications.

Dynamics and thermodynamics of the spherical frustrated Blume-Emery-Griffiths model.

We introduce a spherical version of the frustrated Blume-Emery-Griffiths model and solve exactly the statics and the Langevin dynamics for zero particle-particle interaction (K=0). In this case the model exhibits an equilibrium transition from a disordered to a spin glass phase, which is always continuous for nonzero temperature. The same phase diagram results from the study of the dynamics. Furthermore, we note the existence of a nonequilibrium time regime in a region of the disordered phase, characterized by aging, as occurs in the glassy phase. Due to a finite equilibration time, the system displays in this region the pattern of interrupted aging.

Slow dynamics and aging in a constrained diffusion model.

We carry out a complete analysis of the schematic diffusive model recently introduced for the description of supercooled liquids and glassy systems above the glass temperature. The model is described by a trivial equilibrium measure and the presence of kinetics constraints is mimicked through a rapidly decreasing mobility at high particle density. The governing equation describing a sudden quench process is investigated analytically in a mean field approach and by means of numerical simulations. For deep quenches a long lasting off-equilibrium dynamics is observed in dense systems before equilibration is achieved, where time translational invariance lacks and the system ages. The kinetics is slow in this time domain since the average particle diffusivity D decreases in time, as opposed to the standard diffusion case of a constant D, that is recovered only in equilibrium. The autocorrelation function decays slower than an exponential, falling in mean field as an enhanced power law. The linear response function is computed and the modalities of the break-down of the fluctuation dissipation theorem are analytically investigated, showing that an effective temperature can be defined which slowly approaches the bath temperature from above.

Percolation and Burgers' dynamics in a model of capillary formation.

Capillary networks are essential in vertebrates to supply tissues with nutrients. Experiments of in vitro capillary formation show that cells randomly spread on a gel matrix autonomously organize to form vascular networks. Cells form disconnected networks at low densities and connected ones above a critical density. Above the critical density the network is characterized by a typical mesh size approximately 200 microm, which is approximately constant on a wide range of density values. In this paper we present a full characterization of a recently proposed model which reproduces the main features of the biological system, focusing on its dynamical properties, on the fractal properties of patterns, and on the percolative phase transition. We discuss the relevance of the model in relation with some experiments in living beings and proposed diagnostic methods based on the measurement of the fractal dimension of vascular networks.