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.
Laguna Azul is an oligotrophic lake situated at 4,560 m above sea level and subject to a high level of solar radiation. Bacterioplankton community composition (BCC) was analysed by denaturing gradient gel electrophoresis and the impact of solar ultraviolet radiation was assessed by measuring cyclobutane pyrimidine dimers (CPD). Furthermore, pure cultures of Acinetobacter johnsonii A2 and Rhodococcus sp. A5 were exposed simultaneously and CPD accumulation was studied. Gel analyses generated a total of 7 sequences belonging to Alpha-proteobacteria (1 band), Beta-proteobacteria (1 band), Bacteroidetes (2 bands), Actinobacteria (1 band), and Firmicutes (1 band). DGGE profiles showed minimal changes in BCC and no CPD was detected even though a high level of damage was found in biodosimeters. A. johnsonii A2 showed low level of DNA damage while Rhodococcus sp. A5 exhibited high resistance since no CPD were detected under natural UV-B exposure, suggesting that the bacterial community is well adapted to this highly solar irradiated environment.
High-altitude "ndean lakes are exposed to extreme environmental factors like high salinity, ultraviolet radiation, heavy metals, among others. "s it was previously shown, these lakes are not only the habitat of a high diversity of bacteria with multiple resistances they also support an enormous population of flamingos, which migrate among these wetlands, and they could play a role as disseminators and/or reservoirs of pathogenic bacteria.The aim of this work was to analyze, by Denaturant Gradient Gel Electrophoresis, the bacterial population under selective antibiotic pressure from bacterioplankton and flamingo feces from three lakes, placed between altitudes , and , m. "lmost all bands were present in antibiotic-enriched cultures. Several bands identified in water were found in feces as well, presenting mainly correspondence with Gamma-proteobacteria. Few bands were exclusively identified in water, and those presenting correspondence with Alfa-proteobacteria and "ctinobacteria were only identified in Laguna "zul. This study established that flamingos' enteric biota is in close interaction with lake water and demonstrated that bacteria with the ability to grow in antibiotics are abundant and diverse in the microbiota of "ndean lakes. "dditionally, flamingos could be considered as vectors of pathogenic organisms, since Stenotrophomonas seem to be the widest spread bacteria in the studied lakes.
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