Isolation and characterization of agricultural soil bacteria with biotechnological and biological control potential applications

Unsustainable agricultural practices as the indiscriminate use of agrochemicals to increase crop yield eventually have an impact on soil conditions and their microbiological diversity. To regain balance and improve the efficient use of the natural resources, ecologically sound strategies as those microbe-based can be an alternative. In this work, a collection of bacteria was isolated from agricultural soil and characterized to evaluate their properties for biotechnological and/or biocontrol applications, mainly capacity for phosphorus, nitrogen and iron biofertilization, exoenzyme production, and biological control of several species of phytopathogenic fungi. Bacterial identification pointed out to a majority of Bacillus spp. along with other several minority genera. Isolates globally displayed a high proportion of the biological activities tested, especially concerning production of hydrolytic enzymes such as proteases, lipases, amylases, gelatinases and DNases but, also production of siderophores, and other activities like solubilization of phosphates and fixation of nitrogen. Inhibition on fungal growth was also displayed with variable results among the soil bacterial isolates by production of diffusible compounds and/or VOCs (volatile organic compounds) against the phytopathogenic Verticillium dahliae, Fusarium pseudograminearum, F. oxysporum, Neofusicoccum parvum and Diplodia seriata. One of the isolates also displayed capacity for plant-growth promotion of tomato plants. Evidence from this work provides promise for the application of soil bacterial isolates to improve agricultural soil management and crop production as well as to control diseases and promote plant growth.