Potencial biotecnológico de espécies dos gêneros streptomyces e bacillus isolados dos rios madeira e purus para aplicação agrícola

Abstract

Microorganisms are known for their high capacity to produce bioactive compounds that have a wide range of applications. In addition to the natural products with biotechnological potential produced, many microorganisms have been used in the development of agricultural bio-inputs applied in disease control and plant growth promotion. In this context, the present work aimed to isolate, select and characterize Bacillus and Streptomyces species from sediments of the Madeira and Purus Rivers with potential for the control of phytopathogens. 145 isolates were screened for the formation of inhibition halos against phytopathogenic fungi: Colletotrichum siamense, Fusarium decemcellulare and Moniliophthora perniciosa. Based on the results of antibiosis, 38 isolates were selected for analysis of mycelial growth inhibition (PIC), which ranged from 0 to 90% for at least one of the three phytopathogens. Molecular identification based on the 16S region characterized the isolates with antifungal activity in two genera: Bacillus and Streptomyces. From each genus, three isolates were selected for morphological characterization and activity tests against other pathogens. From the genus Streptomyces, isolates APUR 32.5, MPUR 40.3, MPUR 46.7 were selected, whose multilocus phylogenetic analysis based on gyrB, trpB and 16S region genes indicated them as possible new species. The three Streptomyces isolates were tested against seven other different phytopathogens (Corynespora cassiicola, Colletotrichum guaranicola, Colletotrichum sp., Pseudocercospora fijiensis, Neopestalotiopsis formicarum, Pseudopestalotiopsis gilvanii and Rhizoctonia sp.) indicating that the best performance was against C. guaranicola, with PIC values ranging from 73 to 84%. The three selected Bacillus isolates (MPUR 33.1, MPUR 35.2 and MPUR 44.1), when tested against several phytopathogens, showed better activity against M. perniciosa, with values ranging from 80 to 88%. The Minimum Inhibitory Concentration (MIC) of extracts from Streptomyces isolates showed 100% inhibition against M. perniciosa. The bactericidal action was demonstrated by the extract of the isolate MPUR 40.3 against B. cereus at a concentration of 50 ppm. In addition to their antimicrobial activity, Streptomyces isolates were also shown to produce amylase, cellulase, lipase or protease.