The role of biofilm formation by plant-associated beneficial bacteria in reducing the damage of plant pathogens

Beneficial bacteria protect the plants against pathogens in various strategies. Some of these strategies are included the production of secondary metabolites such as antibiotics, volatile organic compounds and siderophores, plant resistance induction and promoting the plant growth parameters. In recent years, biofilm production has been considered as one of the important features in the survival of plant beneficial bacteria. A biofilm is a community of one or more bacterial species surrounded by polymeric materials. In addition to bacteria, fungi, algae and protozoa may be found in the biofilm. Living in biofilms has many benefits for antagonistic bacteria. Biofilm protects bacteria against adverse nutritional conditions, shortage of available oxygen, high osmotic pressure, sudden changes in temperature and pH, drought stress and antimicrobial compounds such as antibiotics and chlorine compounds. In addition to enhancing the production of effective secondary metabolites in disease biocontrol in biofilm, its matrix provides complete protection of these compounds. Concerning the importance of forming complete and three–dimensional biofilms by beneficial bacteria, and its positive effects on increasing their biocontrol capability, it is suggested that this feature be considered in the screening of beneficial bacteria to select effective strains in biocontrol of plant diseases and their use in commercial production.