Biofilms on Plant Surfaces

Land plants modify the terrestrial environment extensively by nutrient acquisition, water utilization, physical disruption and cohesion of the soil, and the release of complex exudate materials. Decaying plant matter is also a major source of organic material in soils. Large numbers of microorganisms associate with and flourish on, within, and around plants, colonizing virtually all exposed tissues. While some of these microbes may incite disease on certain plants, a large number are harmless or beneficial symbionts. Microbial populations multiply in response to the plant environment and often form multicellular complexes that range from small aggregates to expansive, highly structured biofilms. Plant-associated biofilms have important consequences for plant health and disease, as the microorganisms within these populations may provide benefits or, conversely, damage the host. The structure, activity and microbial diversity harbored within biofilms influence the plant interaction to varying degrees, dependent on plant type, growth stage and environmental conditions. Likewise, plants influence the bacterial population density, fostering communities that interact with each other and the plant through metabolic activity and cell–cell communication mechanisms that allow the microbes to coordinate their activities and optimize their competitive success.