Isolation of Bacteria with Antifungal Activity against the Phytopathogenic Fungi Stenocarpella maydis and Stenocarpella macrospora

Stenocarpella maydis and Stenocarpella macrospora are the causal agents of ear rot in corn, which is one of the most destructive diseases in this crop worldwide. These fungi are important mycotoxin producers that cause different pathologies in farmed animals and represent an important risk for humans. In this work, 160 strains were isolated from soil of corn crops of which 10 showed antifungal activity against these phytopathogens, which, were identified as: Bacillus subtilis, Pseudomonas spp., Pseudomonas fluorescens, and Pantoea agglomerans by sequencing of 16S rRNA gene and the phylogenetic analysis. From cultures of each strain, extracellular filtrates were obtained and assayed to determine antifungal activity. The best filtrates were obtained in the stationary phase of B. subtilis cultures that were stable to the temperature and extreme pH values; in addition they did not show a cytotoxicity effect against brine shrimp and inhibited germination of conidia. The bacteria described in this work have the potential to be used in the control of white ear rot disease

Biochemical study of the extracellular aspartyl protease Eap1 from the phytopathogen fungus Sporisorium reilianum

In this work, the extracellular protease Eap1 from Sporisorium reilianum was characterized in solid and liquid cultures using different culture media. The results showed that Eap1 was produced in all media and under all culture conditions, with the most activity in solid culture at an acidic pH of 3-5. Following purification, the 41 kDa protease demonstrated aspartyl protease activity. The enzyme was stable at a wide range of temperatures and pH values, but 45 C and pH 3 were optimal. The Km and Vmax values obtained were 0.69 mg/mL and 0.66 μmol/min, respectively, with albumin as the substrate. Eap1 degraded hemoglobin as well as proteins obtained from corn germ, roots, stems and slides at pH 3 and also had milk-clotting activity. Sequencing analysis showed that this protein has 100% similarity to the peptide sequence theoretically obtained from the sr11394 gene, which encodes an aspartyl protease secreted by S. reilianum. © 2013 Elsevier Ltd. All rights reserved.Fondo Mixto-Consejo Nacional de Ciencia y Tecnología; the government of the state of Hidalgo (FOMIXCONACyT); Fondo de Ciencia Básica SEP-CONACyTPeer Reviewe