Flavonoid Accumulation Varies in Medicago truncatula in Response to Mercury Stress.

Mercury (Hg) contamination is increasing worldwide in both wild ecosystems and agricultural soils due to natural processes, but mostly to anthropic activities. The molecular mechanisms involved in Hg toxicity and tolerance in plants have been extensively studied; however, the role of flavonoids in response to Hg stress remains to be investigated. We conducted a metabolomic study to analyze the changes induced at the secondary metabolite level in three Hg-tolerant and one Hg-sensitive Medicago truncatula cultivars. A total of 46 flavonoid compounds, classified into five different flavonoid families: anthocyanidins, flavones, isoflavones, pterocarpan flavonoids, and flavanones, along with their respective glycoconjugate derivatives, were identified in leaf and root tissues. The synthesis of free isoflavones, followed by monoglycosylation and further malonylation was shown to be characteristic of root samples, whereas higher glycosylation, followed by further acylation with coumaric and ferulic acid was characteristic of leaf tissues. While minor changes were observed in leaves, significant quantitative changes could be observed in roots upon Hg treatment. Some flavonoids were strongly upregulated in roots, including malonylglucosides of biochanin A, formononetin and medicarpin, and aglycones biochanin, daidzein, and irisolidone. Hg tolerance appeared to be mainly associated to the accumulation of formononetin MalGlc, tricin GlcAGlcA, and afrormosin Glc II in leaves, whereas aglycone accumulation was associated with tolerance to Hg stress in roots. The results evidence the alteration of the flavonoid metabolic profile and their glycosylation processes in response to Hg stress. However, notable differences existed between varieties, both in the basal metabolic profile and in the response to treatment with Hg. Overall, we observed an increase in flavonoid production in response to Hg stress, and Hg tolerance appeared to be associated to a characteristic glycosylation pattern in roots, associated with the accumulation of aglycones and monoglycosylated flavonoids. The findings are discussed in the context of the flavonoid biosynthetic pathway to provide a better understanding of the role of these secondary metabolites in the response and tolerance to Hg stress in M. truncatula.

The classification of Staphylococcus aureus strains by biofilm production differs depending on the method used.

INTRODUCTION: Strains can be classified in terms of biofilm production from quantitative absorbance values collectively by dividing strains into tertile ranks or individually by calculating the optical density for the negative control. However, these methods have not been compared in a large sample of Staphylococcus aureus strains. Therefore, our objective was to analyze the agreement between both methods in terms of biomass production and metabolic activity of their biofilm. METHODS: We classified 233 S. aureus strains by biomass production and metabolic activity using the crystal violet and XTT assays, respectively. Strains were classified as low, moderate, or high biofilm producers according to tertile or optical density. RESULTS: We found no agreement between both methods (p<0.001 and p=0.028, respectively). CONCLUSIONS: We consider strains' biofilm classification by optical density to be a more reliable method, as it depends on the individual absorbance of each strain.

The classification of Staphylococcus aureus strains by biofilm production differs depending on the method used / La clasificación de cepas de Staphylococcus aureus según la producción de biopelícula varía dependiendo del método utilizado

IntroductionStrains can be classified in terms of biofilm production from quantitative absorbance values collectively by dividing strains into tertile ranks or individually by calculating the optical density for the negative control. However, these methods have not been compared in a large sample of Staphylococcus aureus strains. Therefore, our objective was to analyze the agreement between both methods in terms of biomass production and metabolic activity of their biofilm.MethodsWe classified 233 S. aureus strains by biomass production and metabolic activity using the crystal violet and XTT assays, respectively. Strains were classified as low, moderate, or high biofilm producers according to tertile or optical density.ResultsWe found no agreement between both methods (p<0.001 and p=0.028, respectively).ConclusionsWe consider strains’ biofilm classification by optical density to be a more reliable method, as it depends on the individual absorbance of each strain.

IntroducciónLas cepas se pueden clasificar en términos de producción de biopelícula a partir de valores cuantitativos de absorbancia dividiendo de forma colectiva las cepas en rangos por terciles o individualmente calculando la densidad óptica para el control negativo. Sin embargo, estos métodos no se han comparado en una gran muestra de cepas de Staphylococcus aureus. Por lo tanto, nuestro objetivo fue analizar la concordancia entre ambos métodos en términos de producción de biomasa y actividad metabólica de la biopelícula.MétodosSe clasificaron 233 cepas de S. aureus por producción de biomasa y actividad metabólica utilizando los ensayos de cristal violeta y de XTT, respectivamente. Las cepas se clasificaron como altamente, moderadamente o bajamente productoras de biopelícula según terciles o densidad óptica.ResultadosNo encontramos concordancias entre ambos métodos (p<0,001 y p=0,028, respectivamente).ConclusionesConsideramos que la clasificación del biofilm de cepas por densidad óptica es un método más fiable, ya que depende de la absorción individual de cada cepa.

The classification of Staphylococcus aureus strains by biofilm production differs depending on the method used.

INTRODUCTION: Strains can be classified in terms of biofilm production from quantitative absorbance values collectively by dividing strains into tertile ranks or individually by calculating the optical density for the negative control. However, these methods have not been compared in a large sample of Staphylococcus aureus strains. Therefore, our objective was to analyze the agreement between both methods in terms of biomass production and metabolic activity of their biofilm. METHODS: We classified 233 S. aureus strains by biomass production and metabolic activity using the crystal violet and XTT assays, respectively. Strains were classified as low, moderate, or high biofilm producers according to tertile or optical density. RESULTS: We found no agreement between both methods (p<0.001 and p=0.028, respectively). CONCLUSIONS: We consider strains' biofilm classification by optical density to be a more reliable method, as it depends on the individual absorbance of each strain.

Cerebellar involvement in Hodgkin's lymphoma: an atypical site of relapse.

The presentation of intracranial metastases from Hodgkin's lymphoma is an infrequent event that worsens clinical outcome. A case of Hodgkin's lymphoma relapse in the cerebellum is described in a 70-year-old woman with a previously treated stage IVA Hodgkin's lymphoma. Diagnostic workup and treatment strategies for central nervous system relapses are reviewed and discussed. A combination of surgery, radiotherapy and occasionally chemotherapy remains the most appropriate approach to intracranial Hodgkin's lymphoma.