Rhizobacterial Biofilms: Diversity and Role in Plant Health

The diverse nature of rhizobacteria and their interaction with plant roots involves complex processes and provides a unique microbial niche in the rhizosphere both beneficial and harmful to plant health depending on nature of bacteria. Biofilms are defined as the bacterial populations which stick to living and nonliving surfaces and encased in a self-produced extracellular polymeric substances (EPS). Both disease-causing and beneficial plant growth-encouraging bacteria may form biofilm on abiotic and biotic surfaces including plant surface and in soil. It is now well known that a microbe under natural condition forms mixed/polymicrobial biofilm. The process of biofilm development and their regulation are well studied among human pathogenic bacteria such as Pseudomonas aeruginosa. However, recent investigations indicated an increased interest in the research on biofilm on plant-associated rhizobacteria such as Azotobacter, Acinetobacter, Bacillus, Burkholderia, Klebsiella, Pantoea, Pseudomonas and Rhizobium. In this chapter we have made an attempt to review recent studies on rhizobacterial biofilms and their possible impact on plant health under natural and stress conditions.