ABSTRACT
Economic losses caused by postharvest diseases represent one of the main problems of the citrus industry worldwide. The major diseases affecting citrus are the "green mold" and "blue mold", caused by Penicillium digitatum and P. italicum, respectively. To control them, synthetic fungicides are the most commonly used method. However, often the emergence of resistant strains occurs and their use is becoming more restricted because of toxic effects and environmental pollution they generate, combined with trade barriers to international markets. The aim of this work was to isolate indigenous killer yeasts with antagonistic activity against fungal postharvest diseases in lemons, and to determine their control efficiency in in vitro and in vivo assays. Among 437 yeast isolates, 8.5% show to have a killer phenotype. According to molecular identification, based on the 26S rDNA D1/D2 domain sequences analysis, strains were identified belonging to the genera Saccharomyces, Wickerhamomyces, Kazachstania, Pichia, Candida and Clavispora. Killers were challenged with pathogenic molds and strains that caused the maximum in vitro inhibition of P. digitatum were selected for in vivo assays. Two strains of Pichia and one strain of Wickerhamomyces depicted a significant protection (p <0.05) from decay by P. digitatum in assays using wounded lemons. Thus, the native killer yeasts studied in this work showed to be an effective alternative for the biocontrol of postharvest fungal infections of lemons and could be promising agents for the development of commercial products for the biological control industry.
Subject(s)
Citrus/microbiology , Penicillium/physiology , Pest Control, Biological/methods , Plant Diseases/microbiology , Yeasts/physiology , Citrus/growth & development , Phenotype , Plasmids/genetics , Yeasts/geneticsABSTRACT
La Leishmaniasis es una enfermedad parasitaria desatendida causada por hemoflagelados del género Leishmania y transmitida a humanos por la picadura de dípteros de la sub-familia Phlebotomies. Dependiendo de la especie de Leishmania, la enfermedad presenta diferentes formas clínicas incluyendo manifestaciones cutáneas, mucocutáneas y viscerales. En América Latina, la Leishmaniasis Tegumentaria Americana que engloba las formas cutánea y mucocutánea, es endémica desde la península de Yucatán hasta el norte de Argentina, incluida la provincia de Tucumán. El presente estudio tuvo como objetivo realizar el estudio retrospectivo de pacientes con sospecha clínica de Leishmaniasis Tegumentaria (LT) derivados al Departamento Bioquímico-Laboratorio de Salud Pública de San Miguel de Tucumán, durante abril de 2015 a marzo de 2017. Un total de 30 muestras de frotis de lesión y/o biopsia de 23 pacientes fue analizado por microscopía óptica (M.O.) y PCR. Las muestras en las que se detectó banda específica de Leishmania spp. por amplificación de ADN kinetoplastídico (ADNk) fueron sometidas a PCR Específica de Polimorfismo (PS-PCR) para la investigación de subgénero y especie. Además se procedió al análisis de la secuencia del gen de citocromo b para la confirmación de especie. Se diagnosticaron 4 pacientes con LT por M.O. (17,4%). La amplificación del ADNk resultó positiva en 8 pacientes (34,8%). La combinación de M.O. y amplificación del ADNk a partir de muestras de frotis de lesión y tejido de biopsia mejoró notablemente el diagnóstico de LT. Con respecto a los sub-géneros identificados, se detectó que el mismo fue Viannia y las especies asociadas correspondieron a braziliensis
Subject(s)
Leishmania braziliensis , Diagnosis , Leishmania , Molecular BiologyABSTRACT
Xanthomonas citri subsp. citri (Xcc) is the bacterium responsible for citrus canker. This bacterium is exposed to reactive oxygen species (ROS) at different points during its life cycle, including those normally produced by aerobic respiration or upon exposition to ultraviolet (UV) radiation. Moreover, ROS are key components of the host immune response. Among enzymatic ROS-detoxifying mechanisms, catalases eliminate H2O2, avoiding the potential damage caused by this specie. Xcc genome includes four catalase genes. In this work, we studied the physiological role of KatG, the only bifunctional catalase of Xcc, through the construction and characterization of a modified strain (XcckatG), carrying an insertional mutation in the katG gene. First, we evaluated the involvement of KatG in the bacterial adaptive response to H2O2. XcckatG cultures exhibited lower catalase activity than those of the wild-type strain, and this activity was not induced upon treatment with sub-lethal doses of H2O2. Moreover, the KatG-deficient mutant exhibited decreased tolerance to H2O2 toxicity compared to wild-type cells and accumulated high intracellular levels of peroxides upon exposure to sub-lethal concentrations of H2O2. To further study the role of KatG in Xcc physiology, we evaluated bacterial survival upon exposure to UV-A or UV-B radiation. In both conditions, XcckatG showed a high mortality in comparison to Xcc wild-type. Finally, we studied the development of bacterial biofilms. While structured biofilms were observed for the Xcc wild-type, the development of these structures was impaired for XcckatG. Based on these results, we demonstrated that KatG is responsible for Xcc adaptive response to H2O2 and a key component of the bacterial response to oxidative stress. Moreover, this enzyme plays an important role during Xcc epiphytic survival, being essential for biofilm formation and UV resistance.
