Biocontrol and plant growth-promoting activities of airborne bacteria

The potential of airborne bacteria as a sustainable alternative for agriculture was evaluated. Bacteria were isolated from air samples and evaluated for their plant growth-promoting (PGPB) and antifungal properties as biocontrol of phytopathogens. Results showed that diverse bacterial species, including Exiguobacterium, Rhodococcus, Kocuria, and Staphylococcus genera, exhibited PGPB activities such as phosphorus solubilization, siderophore production, and auxin production. Kocuria strains showed high auxin production. Rhodococcus sp. was observed to significantly promote root growth and the formation of beneficial biofilms on bean roots. Additionally, this bacterium opened the xylem vessels, facilitating the absorption of nutrients and water. Kocuria sp. strains exhibited high antifungal activity against Fusarium oxysporum and Phytophthora cinnamomi due to volatile organic compounds (VOCs) produced by these strains. Volatile profile revealed compounds such as dimethyl disulfide, pyrazines, and benzaldehyde derivatives associated with fungal growth inhibition. This study demonstrates the potential of airborne bacteria as both biofertilizers (producers of indole-3-acetic acid IAA, potassium, and phosphorus solubilizers, siderophore producers, and ammonium producers) and biocontrol agents (against the phytopathogenic fungus Fusarium oxysporum and Phytophthora cinnamomi).