Botrytis cinerea is the causing agent of plant gray mold disease. This aggressive fungal phytopathogen is necrotrophic and could infect almost all the vegetable and fruit crops. Each year, the gray mold disease causes an estimated loss of $10-100 billion worldwide. Beneficial bacteria may provide effective biocontrol against B. cinerea by direct and indirect antagonistic interactions. Here we show that two novel Gram-positive Bacillus spp. (named OSUB3 and OSUB22 respectively), which are originally isolated from plant roots, can inhibit B. cinerea growth and further disable its pathogenicity on susceptible host plants including Arabidopsis and tomato. We hypothesize that these Bacillus spp. strategically deliver extracellular exudates against B. cinerea growth and infection. The main goal of this project is to identify and characterize new active metabolites from theses Bacillus exudates, which can thus further be developed and applied to control the gray mold disease strategically. The goal will be achieved with the integrated approaches, including the genomics, metabolomics, bioinformatics, and infectious disease biology. Natural compounds produced by Bacillus spp. are believed to have less environmental persistence and low mammalian toxicity. This approach provides a promising alternative to chemical pesticides that are widely used in agriculture, considering that those synthetic chemicals pose great threats to both human health and the environment. The outcome of this research will contribute to manage the gray mold disease in a more effective and sustainable way.