Interactions between Head Blight Pathogens: Consequences for Disease Development and Toxin Production in Wheat Spikes

Head blight (HB) is one of the most damaging diseases on wheat, inducing significant yield losses and toxin accumulation in grains. Fungal pathogens responsible for HB include the genus Microdochium, with two species, and the toxin producer genus Fusarium, with several species. Field studies and surveys show that two or more species can coexist within a same field and coinfect the same plant or the same spike. In the current study, we investigated how the concomitant presence of F. graminearum and another of the HB complex species influences the spike colonization and the toxin production by the fungi. To study these interactions, 17 well-characterized isolates representing five species were inoculated alone or in pairs on wheat spikes in greenhouse and field experiments. The fungal DNA in the grains was estimated by quantitative PCR and toxin contents (deoxynivalenol and nivalenol) by ultraperformance liquid chromatography-UV detection-tandem mass spectrometry. The responses of the different isolates to the presence of a competitor were variable and isolate specific more than species specific. The development of the most aggressive isolates was either unchanged or a slightly increased, while the development of the less aggressive isolates was reduced. The main outcome of the study was that no trend of increased toxin production was observed in coinoculations compared to single inoculations. On the contrary, the amount of toxin produced was often lower than expected in coinoculations. We thus conclude against the hypothesis that the co-occurrence of several HB-causing species in the same field might aggravate the risk linked to fusarium toxins in wheat production.     

An experimental study of the S-Allee effect in the self-incompatible plant <Emphasis Type="Italic">Biscutella neustriaca</Emphasis>

Homomorphic self-incompatibility (SI) evolved in many plant families to enforce selfing avoidance, and is controlled by a single multiallelic locus (the S-locus). In a fragmented landscape, strong variation in population size and in local density is expected to cause strong variation in allelic diversity at the S-locus, which could generate an Allee effect on female reproductive success by constraining compatible pollen availability. In this experimental study, we aimed at detecting this SI-specific Allee effect (or S-Allee effect) in the endangered species Biscutella neustriaca. We demonstrated the occurrence of a SI mating system in the species and determined compatibility relationships among genotypes through a large set of controlled pollinations. For the experiment, we chose three different pollen receptor genotypes, each compatible with respectively 100, 75 and 25% of four other genotypes, which constituted the pollen sources. We placed different ramets of each receptor at different distances from the pollen sources to control for pollen limitation due to low local density, and we measured the seed set on each receptor plant three times consecutively. Analyses performed with generalized linear mixed models showed that both the distance to the pollen sources and the mate availability due to SI had a significant effect on seed set, with a strong reduction observed when mate availability was limited to 25%. Our results suggest that pollen limitation due to a restriction in compatible mate availability could occur in small or scattered populations exhibiting low allelic diversity at the S-locus.     

Genetic changes during a laboratory adaptive evolution process that allowed fast growth in glucose to an Escherichia coli strain lacking the major glucose transport system

ABSTRACT: BACKGROUND: Escherichia coli strains lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS), which is the major bacterial component involved in glucose transport and its phosphorylation, accumulate high amounts of phosphoenolpyruvate that can be diverted to the synthesis of commercially relevant products. However, these strains grow slowly in glucose as sole carbon source due to its inefficient transport and metabolism. Strain PB12, with 400 % increased growth rate, was isolated after a 120 hours adaptive laboratory evolution process for the selection of faster growing derivatives in glucose. Analysis of the genetic changes that occurred in the PB12 strain that lacks PTS will allow a better understanding of the basis of its growth adaptation and, therefore, in the design of improved metabolic engineering strategies for enhancing carbon diversion into the aromatic pathways. RESULTS: Whole genome analyses using two different sequencing methodologies: the Roche NimbleGen Inc. comparative genome sequencing technique, and high throughput sequencing with Illumina Inc. GAIIx, allowed the identification of the genetic changes that occurred in the PB12 strain. Both methods detected 23 non-synonymous and 22 synonymous point mutations. Several non-synonymous mutations mapped in regulatory genes (arcB, barA, rpoD, rna) and in other putative regulatory loci (yjjU, rssA and ypdA). In addition, a chromosomal deletion of 10,328 bp was detected that removed 12 genes, among them, the rppH, mutH and galR genes. Characterization of some of these mutated and deleted genes with their functions and possible functions, are presented. CONCLUSIONS: The deletion of the contiguous rppH, mutH and galR genes that occurred simultaneously, is apparently the main reason for the faster growth of the evolved PB12 strain. In support of this interpretation is the fact that inactivation of the rppH gene in the parental PB11 strain substantially increased its growth rate, very likely by increasing glycolytic mRNA genes stability. Furthermore, galR inactivation allowed glucose transport by GalP into the cell. The deletion of mutH in an already stressed strain that lacks PTS is apparently responsible for the very high mutation rate observed.     

Levels of Intervention: How Are They Used in Quebec Hospitals?

In order to promote better practices and communication around end-of-life decision-making, several Canadian hospitals in the province of Quebec have developed a tool called “Levels of Intervention” (LOI). No work to date has been published demonstrating improvement since these forms were implemented. The purpose of the present study was to obtain information about the use of LOI forms across Quebec hospitals and to identify gaps in practice as well as areas for improvement. A retrospective study was undertaken of 299 charts of patients who had died in three Quebec hospitals with a LOI ordered. Results were analysed through a principlism ethical framework. High compliance with the level of intervention ordered at the time of death was recorded, as well as high involvement of patient and/or family, demonstrating the efficiency of LOI in promoting respect for autonomy. Other results show delays in end-of-life care discussions in the course of the hospitalization. Only a small proportion of patients who died had a palliative care consultation, which may reflect equity issues in access to care. This study highlights the importance of the LOI in Quebec and the role it is playing in respect for end-of-life preferences as well as in the involvement of patients and families in the decision-making process. Training specific to end-of-life decision-making conversations would help support the LOI form’s use, as would developing provincial or national guidelines on the use of LOI to standardize organizational policies and practice around end-of-life care.     

Metabolic engineering for improving anthranilate synthesis from glucose in Escherichia coli

Background  

Anthranilate is an aromatic amine used industrially as an intermediate for the synthesis of dyes, perfumes, pharmaceuticals and other classes of products. Chemical synthesis of anthranilate is an unsustainable process since it implies the use of nonrenewable benzene and the generation of toxic by-products. In Escherichia coli anthranilate is synthesized from chorismate by anthranilate synthase (TrpED) and then converted to phosphoribosyl anthranilate by anthranilate phosphoribosyl transferase to continue the tryptophan biosynthetic pathway. With the purpose of generating a microbial strain for anthranilate production from glucose, E. coli W3110 trpD9923, a mutant in the trpD gene that displays low anthranilate producing capacity, was characterized and modified using metabolic engineering strategies.     

Homolactic fermentation from glucose and cellobiose using Bacillus subtilis

Backgroung  

Biodegradable plastics can be made from polylactate, which is a polymer made from lactic acid. This compound can be produced from renewable resources as substrates using microorganisms. Bacillus subtilisis a Gram-positive bacterium recognized as a GRAS microorganism (generally regarded as safe) by the FDA. B. subtilisproduces and secretes different kind of enzymes, such as proteases, cellulases, xylanases and amylases to utilize carbon sources more complex than the monosaccharides present in the environment. Thus, B. subtiliscould be potentially used to hydrolyze carbohydrate polymers contained in lignocellulosic biomass to produce chemical commodities. Enzymatic hydrolysis of the cellulosic fraction of agroindustrial wastes produces cellobiose and a lower amount of glucose. Under aerobic conditions, B. subtilisgrows using cellobiose as substrate.