Isolation and characterization of soil microorganisms from two National Parks located in the middle of the Mediterranean area as potential biocontrol agents

Biological control for plant disease, the direct or indirect inhibition of diseases by microorganisms, can be considered an interesting tool for sustainable development (1,2). Bacteria are the most abundant living microorganisms in the soil, containing the enzymatic set able to degrade the organic matter. In fact, the fungal cell wall is mainly composed of chitin, glucans, mannans, and glycoproteins that can be degraded by chitinolytic or cellulolytic bacteria. This study aims to isolate organic matter degrading bacteria from soil and to evaluate their potential biocontrol activity against phytopathogenic fungi. Soil samples were collected in the area of Pollino National Park and Sila National Park; bacteria were isolated for the capacity to grow on selective lignocellulosic medium, they are characterized microbiologically and enzymatically through Iodine test solution, betaglucosidase and N-acetyl-glucosaminidase assays. Moreover, bacterial strains were tested for resistance to heavy metals and petroleum derivates (toluene). The biocontrol capacity against phytopathogenic fungi was evaluated. Sequencing analyses have been started for the taxonomic identification of bacteria. A total of 150 bacterial strains, 75 belonging to the Pollino soil and 75 from Sila soil, were isolated. Bacteria were analyzed for their cellulolytic potential activity by Lugol test: a total of 22 strains (16 from Pollino massif and 6 from Sila plateau) showed cellulolytic activity in culture supernatant after growth in carboxymethyl cellulose (soluble cellulose). Some of 22 strains form a halo at Lugol test after growth in AVICEL (crystallin cellulose). The set of 22 bacterial strains were subjected to taxonomic analyses through 16S rDNA gene sequencing: homology sequences were detected by Ribosomal Database and BLAST. The beta-glucosidase and the N-acetyl-glucosaminidase activities were quantified in supernatant spectrophotometrically. Among all the isolated bacteria, an interesting number of these strains significantly inhibited the growth of both Fusarium sambucinum and Fusarium cerealis. Within the ONFOODS project, 150 soil bacterial strains belonging to the area of southern Italy were isolated and characterized for the first time. Some of them showed interesting activity, suggesting they could be used as biocontrol agents.