Transcriptional Responses of Herbaspirillum seropedicae to Environmental Phosphate Concentration

Herbaspirillum seropedicae is a nitrogen-fixing endophytic bacterium associated with important cereal crops, which promotes plant growth, increasing their productivity. The understanding of the physiological responses of this bacterium to different concentrations of prevailing nutrients as phosphate (Pi) is scarce. In some bacteria, culture media Pi concentration modulates the levels of intracellular polyphosphate (polyP), modifying their cellular fitness. Here, global changes of H. seropedicae SmR1 were evaluated in response to environmental Pi concentrations, based on differential intracellular polyP levels. Cells grown in high-Pi medium (50 mM) maintained high polyP levels in stationary phase, while those grown in sufficient Pi medium (5 mM) degraded it. Through a RNA-seq approach, comparison of transcriptional profiles of H. seropedicae cultures revealed that 670 genes were differentially expressed between both Pi growth conditions, with 57% repressed and 43% induced in the high Pi condition. Molecular and physiological analyses revealed that aspects related to Pi metabolism, biosynthesis of flagella and chemotaxis, energy production, and polyhydroxybutyrate metabolism were induced in the high-Pi condition, while those involved in adhesion and stress response were repressed. The present study demonstrated that variations in environmental Pi concentration affect H. seropedicae traits related to survival and other important physiological characteristics. Since environmental conditions can influence the effectiveness of the plant growth-promoting bacteria, enhancement of bacterial robustness to withstand different stressful situations is an interesting challenge. The obtained data could serve not only to understand the bacterial behavior in respect to changes in rhizospheric Pi gradients but also as a base to design strategies to improve different bacterial features focusing on biotechnological and/or agricultural purposes

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Screening faba bean for chocolate spot resistance: Evaluation methods and effects of age of host tissue and temperature

Chocolate spot is an important disease of faba bean (Vicia faba) caused by the necrotrophic fungus Botrytis fabae. The aims of this work were: i) to compare different methods of screening for resistance; ii) to assess the influence of the age of host tissue and temperature on this pathosystem. To this effect, a collection of 42 faba bean accessions was evaluated in mature plant stage in the field in Cordoba (Southern Spain) and in detached leaflet and whole plant tests under controlled conditions. Field results correlated better with those of the whole plant test than with those of the detached leaflet assay. Integration of results from the field and whole plant experiments resulted in the selection of six accessions of interest as sources of resistance. Influence of leaf age on disease development was found to be genotype dependent. Older leaves were more susceptible than younger ones in 23 accessions, while no difference between leaf ages was detected in the remaining accessions. The effects of plant age and temperature were assessed by a whole plant test on seven accessions at two plant ages (4 and 7 weeks) and three temperatures (13, 20, and 25°C). Results showed that the differential genotypic responses to B. fabae were not significantly influenced by either plant age or temperature, although there was a tendency towards lower susceptibility to chocolate spot in faba bean plants as they become older. Further, a partial high-temperature, young-plant resistance was detected. © 2011 KNPV.Financial support by Spanish project AGL2008-01239 is acknowledged.Peer Reviewe

Mechanism of resistance in faba bean (Vicia faba) against broomrape species

Trabajo presentado en la International Conference Advances in grain legume breeding, cultivations and uses for a more competitive value-chain, celebrada en Novi Sad (Serbia) el 27 y 28 de septiembre de 2017.Broomrapes are weedy root parasitic plants that severely constraint faba bean (Vicia faba) production in Mediterranean basin. The most widely distributed species affecting faba bean is Orobanche crenata, although O. foetida and Phelipanche aegyptiaca are of local importance. Extensive and long efforts have been made by breeders, but unfortunately only moderately resistant cultivars are available to farmers. Here we summarize a series of experiments intending to characterize the resistance mechanisms involved in accessions with varying levels of resistance earlier reported. In a first rhyzotron experiment we studied the responses of six faba bean accession against O. crenata, O. foetida and P. aegyptiaca. A proportion of broomrape radicles successfully contacting faba bean roots might later become necrotic and fail the tubercle development against a Spanish O. crenata population. Formed broomrape tubercles might later become necrotic, mainly in the case of some of the resistant faba bean accessions to the Spanish O. crenata and to P. aegyptiaca but not to a Syrian O. crenata or to O. foetida. There was little effect on induction of seed germination. In an attempt to go deeper in the germination step a separate series of experiments was performed with other accessions allowing the identification of accessions inducing low germination of O. crenata, O. foetida and P. aegyptiaca, a mechanism that we consider most promising and we are combining with the other ones in our breeding program.N

Multiple-disease resistance in Vicia faba: Multi-environment field testing for identification of combined resistance to rust and chocolate spot

The aim of this work was to identify Vicia faba germplasm resistant both to rust and chocolate spot. A collection of 43 accessions of V. faba previously identified as chocolate-spot resistant was evaluated for rust and chocolate spot resistance in Egypt and in Spain. The genotype and genotype × environment (GGE) biplot analyses allowed the selection of 11 accessions resistant to both diseases in those locations. These 11 accessions were evaluated for rust in an additional field trial in Spain, all performing better than the susceptible check. The joint analysis of the 11 accessions in the four field trials where they had been evaluated revealed no significant effects either for genotype, environment or the genotype × environment interaction. They are hence promising sources of resistance, both for their low severities and their stable responses across the studied environments. This collection was also tested under controlled conditions against the Egyptian and the Spanish isolates of rust present in the field trials further underlining the stable performance of these genotypes. Finally, the effect of previous infection with chocolate spot on rust resistance was assessed under controlled conditions and no influence of it was found. © 2011 Elsevier B.V.Peer Reviewe

Polyphosphate Degradation in Stationary Phase Triggers Biofilm Formation via LuxS Quorum Sensing System in <em>Escherichia coli</em>

<div><p>In most natural environments, association with a surface in a structure known as biofilm is the prevailing microbial life-style of bacteria. Polyphosphate (polyP), an ubiquitous linear polymer of hundreds of orthophosphate residues, has a crucial role in stress responses, stationary-phase survival, and it was associated to bacterial biofilm formation and production of virulence factors. In previous work, we have shown that <em>Escherichia coli</em> cells grown in media containing a critical phosphate concentration >37 mM maintained an unusual high polyP level in stationary phase. The aim of the present work was to analyze if fluctuations in polyP levels in stationary phase affect biofilm formation capacity in <em>E. coli</em>. Polymer levels were modulated by the media phosphate concentration or using mutant strains in polyP metabolism. Cells grown in media containing phosphate concentrations higher than 25 mM were defective in biofilm formation. Besides, there was a disassembly of 24 h preformed biofilm by the addition of high phosphate concentration to the medium. These phenotypes were related to the maintenance or re-synthesis of polyP in stationary phase in static conditions. No biofilm formation was observed in <em>ppk⁻ppx⁻</em> or <em>ppk⁻ppx⁻</em>/<em>ppk⁺</em> strains, deficient in polyP synthesis and hydrolysis, respectively. <em>luxS</em> and <em>lsrK</em> mutants, impaired in autoinducer-2 quorum sensing signal metabolism, were unable to form biofilm unless conditioned media from stationary phase wild type cells grown in low phosphate were used. We conclude that polyP degradation is required for biofilm formation in sufficient phosphate media, activating or triggering the production of autoinducer-2. According to our results, phosphate concentration of the culture media should be carefully considered in bacterial adhesion and virulence studies.</p> </div

Prospects for durability of available resistances to fungal diseases and parasitic weeds in pea and faba bean

Trabajo presentado en la International Conference Advances in grain legume breeding, cultivations and uses for a more competitive value-chain, celebrada en Novi Sad (Serbia) el 27 y 28 de septiembre de 2017.Peas and faba beans, as any other crops, can be damaged by a number of diseases. Breeders have explored a range of strategies to exploit available resistances, that unfortunately use to be scarce, incomplete and of limited heritability. As a result, only cultivars with moderate levels of resistance are available to farmers in most instances. This is further complicated by the fact that several clearly distinct species (i.e. Orobanche crenata and O. foetida; Uromyces viciae-fabae and U. pisi; Erysiphe pisiand E. trifolii) can infect the same legume crop. Here we will revise current status of resistance in pea and faba bean to a number of fungal diseases and parasitic weeds discussing historic and recent achievements, with a special focus on potential durability.N

Biofilm formation by <i>luxS</i> mutant in conditioned media.

<p><i>luxS⁻</i> cells growing in MT medium during 24 h were reinoculated in wild type MT CM or MT+P CM and in <i>ppk⁻ppx⁻</i> MT CM from different growth times, as indicated. Biofilm formation was determined 24 h after the shift to CM. 48 h MT cultures were used as control (–). Different letters indicate significant differences according to Tukey's test with a <i>p</i>-value of 0.05.</p

Biofilm formation after reinoculation in CM.

*<p>Biofilm formation was determined 24 h after the cells transference to CM. 48 h MT cultures were used as control. Different letters indicate significant differences according to Tukey's test with a <i>p</i>-value of 0.05.</p

Biofilm formation after changes of phosphate concentration in stationary phase.

<p>Biofilm formation by MC4100 was measured at indicated times of growth in MT and in MT with the addition of 40 mM phosphate buffer pH 7 at 24 h (MT+24P) or at 48 h (MT+48P) (<b>left panel</b>), or in MT+P and in MT+P culture switched to fresh MT at 24 h (MT+P→24MT) (<b>right panel</b>). Result represents the mean ± SD of at least three independent experiments performed in triplicate. Different letters indicate significant differences according to Tukey's test with a <i>p</i>-value of 0.05.</p